RADIO ASTRONOMY Journal of the Society of Amateur Radio Astronomers March – April 2014
March- April 2014
Radio Astronomy
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Radio Waves
President’s Page Editors’ Notes
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Bill Lord SARA President
Melinda Lord Editor
Whitham D. Reeve Contributing Editor
Christian Monstein Contributing Editor Stan Nelson Contributing Editor Radio Astronomy is published bimonthly as the official journal of the Society of Amateur Radio Astronomers. Duplication of uncopyrighted material for educational purposes is permitted but credit shall be given to SARA and to the specific author. Copyrighted materials may not be copied without written permission from the copyright owner.
Radio Astronomy is available for download only by SARA members from the SARA web site and may not be posted anywhere else.
It is the mission of the Society of Amateur Radio Astronomers (SARA) to: Facilitate the flow of information pertinent to the field of Radio As‐ tronomy among our members; Promote members to mentor newcomers to our hobby and share the excitement of radio astronomy with other interested persons and organizations; Promote individual and multi station observing programs; Encourage programs that enhance the technical abilities of our members to monitor cosmic radio signals, as well as to share and analyze such signals; Encourage educational programs within SARA and educational outreach initiatives. Founded in 1981, the Society of Amateur Radio Astronomers, Inc. is a membership supported, non‐profit [501(c) (3)], educational and scientific corporation.
Copyright © 2014 by the Society of Amateur Radio Astronomers, Inc. All rights reserved On the Cover‐ Image credits: Mike Peel, Jodrell Bank Centre for Astrophysics, University of Manchester. The Mark 1 Lovell Telescope is located at Jodrell Bank in Lower Withington, Cheshire, England. It is the third largest steerable radio telescope in the world. http://www.jb.man.ac.uk/
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March- April 2014
News
Mark Your Calendar SARA Annual Conference at NRAO Keynote Speaker Abstracts Tentative Schedule Ladies Outings Door Prizes Officer and Director Nominations Radio Jove Conference Abstracts Tentative Radio JOVE Meeting Schedule SARA at Claremore Hamfest Western Conference Report
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Feature Articles
Radio Astronomy Receivers‐ Bruce Randall 30 Noise|| Noise: Y‐factor versus Signal‐to‐Noise Ratio Christian Monstein and Whitham D. Reeve 37 Radio, Magnetic and (Possible) X‐Ray Observations of the X1 Solar Flare on 29 March 2014‐ Whitham D. Reeve 41 Detection of Jovian VLF Noise‐ John Avellone 48 FM notch filter in front & behind the low noise amplifier of a Callisto Radio Spectrometer in Gauribidanur, India‐ Christian Monstein 58 An Antenna with an Historical Past‐ Jeffrey M. Lichtman 61 Report from an expert meeting at United Nations Office for Outer Space Affairs (UNOOSA)‐ Christian Monstein 64 Transmission Line Details ~ Software Calculator Review Whitham D. Reeve 68 Improving long time stability of a radio astronomy receiver Christian Monstein 75 Old Tool, New Use: GPS and the Terrestrial Reference Frame Alex H. Kasprak 78 Strong RFI observed in protected 21 cm band at Zurich 80 Observatory, Switzerland‐ Christian Monstein RASDR update‐ Paul Oxley, Bogdan Vacaliuc, David Fields, Carl Lyster, Stan Kurtz, and Zydrunas Tamosevicius 83 Great Projects to Get Started in Radio Astronomy 87
Membership
New Members Membership Dues & Promotion
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Administrative
Officers, directors and additional SARA contacts
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Resources
New Web Links Education Links and Resources Online Resources For Sale, Trade and Wanted
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Radio Waves
President’s Page
SARA dues are up for renewal June 30 and are still just $20 a year. Your dues fund student and teacher grants for radio astronomy projects. The following e‐mail from a student illustrates the success of the grant program. Anthony used a SuperSID for his project. “I wanted to share some amazing news with you. Last year I went to the International Science and Engineering Fair for my project “A practical notification system to identify incoming sudden ionospheric disturbances”. This year I applied to the Junior Science and Humanities Symposium with this project and won 1st place in the category of engineering. Before even competing in the fair my paper was carefully reviewed from a grouping of 300 applicants which were then narrowed down to 50. After winning first place in my category I went up against the other 1st place winners in other categories a total of 10 other students and out of these 10 I was 2nd place in fair. For this achievement I am awarded a $1,500 dollar scholarship and also a spot as a presenter at the National JSHS (Junior Science and Humanities Symposia) in Washington D.C. April 23‐27 where I will compete against other students in the engineering category for more scholarship money and a trip to London. Thanks for all your help and support you have been able to give me! It really was astounding having the ability to have my work published in the ISWI (International Space Weather Initiative).” From, Anthony Bisulco Your dues also fund outreach like the 2014 USA Science & Engineering Festival. This is the largest and only national Science & Engineering Festival, with the goal to re‐invigorate the interest of our nation's youth in science, technology, engineering and math (STEM) by presenting the most compelling, educational and entertaining science festival in the United States. This event took place April 25to 27 in Washington, DC. and SARA had a booth. SARA and The Radio JOVE Project will have a booth again at the Dayton Hamvention May 16 to 18 at the Hara Arena in Dayton, Ohio. We will again be in the Ball Arena booth BA0421 (near ARRL.) Stop in and say “hi” and you can pay your SARA dues renewal. We will have SuperSID and Radio JOVE kits available for sale as well as CD’s and back issues of the Proceedings. The Annual Conference is set for June 29 to July 2, 2014 at the National Radio Astronomy Observatory in Green Bank, West Virginia. The Radio Jove Team will be holding a conference following us on July 2 to July 4. SARA members are invited to attend along with Radio Jove enthusiasts. More details will be made available on‐line at http://www.radio‐astronomy.org/meetings and in the next Journal. Until next time, happy monitoring, Bill Lord KJ4SKL
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Editor’s Notes We are always looking for basic radio astronomy articles, radio astronomy tutorials, theoretical articles, application and construction articles, news pertinent to radio astronomy, profiles and interviews with amateur and professional radio astronomers, book reviews, puzzles (including word challenges, riddles, and crossword puzzles), anecdotes, expository on “bad astronomy,” articles on radio astronomy observations, suggestions for reprint of articles from past journals, book reviews and other publications, and announce‐ ments of radio astronomy star parties, meetings, and outreach activities. If you would like to write an article for Radio Astronomy, please follow the Author’s Guide on the SARA web site: http://www.radio‐astronomy.org/publicat/RA‐JSARA_Author’s_ Guide.pdf. Please note that the new version of the Author’s Guide includes several changes, mostly dealing with article images. Let us know if you have questions; we are glad to assist authors with their articles and papers and will not hesitate to work with you. You may contact your editors any time via email here: editor@radio‐ astronomy.org.
Please consider submitting your radio astronomy observations for publication: any object, any wavelength. Strip charts, spectrograms, magnetograms, meteor scatter records, space radar records, photographs; examples of radio frequency interference (RFI) are also welcome. Guidelines for submitting observations may be found here: http://www.radio‐astronomy.org/publicat/RA‐ JSARA_Observation_Submission_Guide.pdf Tentative Radio Astronomy due dates and distribution schedule Issue Articles Radio Waves Review Distribution Jan – Feb February 12 February 20 February 23 February 28 Mar – Apr April 12 April 20 April 25 April 30 May – Jun June 10 June 10 June 20 June 30 Jul – Aug August 12 August 20 August 25 August 31 Sep – Oct October 12 October 20 October 25 October 31 Nov – Dec December 12 December 15 December 20 December 31
HELP WANTED Want to see all the great Journal articles before anyone else? We are looking for an editor(s) for the SARA Journal. We have three very active contributing editors who write papers for the Journal and need someone who will combine all of the submittals. You do not have to be a radio astronomy expert. We have members willing to review technical articles submitted for publication. If you are interested in the position, please contact Bill Lord president@radio‐astronomy.org or call 319‐591‐ 1131.
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Mark Your Calendar April 26‐27, 2014 USA Science & Engineering Festival, Walter E. Washington Convention Center in Washington, D.C. SARA Booth 2061 http://www.usasciencefestival.org/ May 16‐18, 2014 Dayton, Ohio Hamvention http://www.hamvention.org/index.php SARA will be in booth BA0421 at this event. Contact Bill Lord at ap_guardian_at_yahoo.com to volunteer. June 6, 2014 Astronomy on the National Mall, Washington, DC This event is hosted by Hofstra University, Department of Physics and Astronomy. Contact Bill Lord at ap_guardian_at_yahoo.com to volunteer. June 29‐ July 2, 2014 SARA Annual Conference, National Radio Astronomy Observatory, Green Bank, West Virginia http://www.radio‐astronomy.org/?q=node/124 July 2‐ July 4, 2014 Radio Jove Conference, National Radio Astronomy Observatory, Green Bank, West Virginia http://www.radio‐astronomy.org/?q=node/124 July 17‐19, 2014 ARRL National Centennial Convention, Hartford, Connecticut https://www.regonline.com/builder/site/Default.aspx?EventID=1248082 Contact Bill Lord at ap_guardian_at_yahoo.com to volunteer. Do you have an event to share with SARA members? Send information to editor@radio‐astronomy.org to be included in the next issue.
Understanding Engineers #3 A priest, a doctor, and an engineer were waiting one morning for a particularly slow group of golfers. The engineer fumed, "What's with those guys? We must have been waiting for fifteen minutes!" The doctor chimed in, "I don't know, but I've never seen such inept golf!" The priest said, "Here comes the greens keeper. Let's have a word with him." He said, "Hello George, What's wrong with that group ahead of us? They're rather slow, aren't they?" The greens keeper replied, "Oh, yes. That's a group of blind firemen. They lost their sight saving our clubhouse from a fire last year, so we always let them play for free anytime!." The group fell silent for a moment. The priest said, "That's so sad. I think I will say a special prayer for them tonight." The doctor said, "Good idea. I'm going to contact my ophthalmologist colleague and see if there's anything she can do for them." The engineer said, "Why can't they play at night?"
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2014 SARA Annual Conference to be Held June 29 to July 2 Radio Jove Conference July 2 to 3 at National Radio Astronomy Observatory, Green Bank, West Virginia, USA
Conference Registration Fees: This year the Radio Jove Conference will be held immediately after the SARA conference. Anyone interested in radio astronomy is invited to attend either or both conferences. The fee for the 2014 SARA Conference has been set at U$165 for all registered participants. This fee includes Conference registration, payment of your 2015 SARA membership dues, and one copy of the published Conference Proceedings (to be distributed at the meeting), morning coffee breaks, afternoon snack breaks, evening refreshments, and eight meals, as indicated below. Please note that all SARA 2014 memberships expire on 15 June 2014. Since SARA Membership Dues are now inseparable from Conference registration; all registered attendees automatically become SARA Members in Good Standing through 15 June 2015. SARA Life Members, or those who have already paid their 2015 membership dues prior to registering, may deduct $20 from the above amount. Those registered for the 2014 Conference who subsequently purchase a Life Membership anytime during the 2014~2015 membership year may deduct $20 from the Life Member Fee (currently set at US$400). And, because SARA offers a special membership rate of US$5.00 for students, all fulltime students under the age of 18 may deduct US$5.00 from the above Conference registration fee. The attendance fee for an accompanying family member (non‐participating spouse, child, or companion of a registered Conference attendee) is US$80, which includes morning coffee breaks, afternoon snacks, evening refreshments, and meals. The cited fees are calculated on a break‐even basis, and apply only to advance registrations received prior to 31 May 2014. All registrations received thereafter are subject to an additional late registration fee, as indicated below. The Radio Jove Conference will be held directly following the SARA Conference on July 2 to July 4. The fee for the Radio Jove conference has been set at $75.00 for both participants and non‐participating guests or spouses. This fee includes morning coffee breaks, afternoon snack breaks, evening refreshments, and six meals, as indicated below.
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Included Meal Plan: Green Bank is a small community with few dining establishments. Thus, SARA has arranged for conference registration to include a meal plan at the NRAO employee's cafeteria, to include: • • •
Dinner Sunday night Breakfast / Lunch / Dinner Monday and Tuesday Breakfast on Wednesday
Radio Jove conference registration includes a meal plan at the NRAO employee's cafeteria, to include: • • •
Lunch / Dinner Wednesday Breakfast / Lunch / Dinner Thursday Breakfast on Friday
The NRAO Cafeteria is not a public dining facility, does not sell individual meals to visitors, and is, in fact, doing us a favor in allowing our group to use their cafeteria at all. Thus, the Meal Plan is an integral part of, and inseparable from, Conference Registration. Please note that, in addition to the above meals, the Conference fee (or Accompanying Person fee) includes refreshments and coffee breaks during the Conference presentations, and snacks and beverages in the Drake Lounge in the evenings. Exceptions to the meal plan will be considered on a case‐by‐case basis, for those Conference attendees residing on site, or others with special dietary needs. Please contact our Treasurer directly with your specific requests. In general, except under unusual circumstances, one should consider the cost of meals to be a part of, and inseparable from, the conference registration fee. Conference Proceedings: Once again this year, a formal, printed Proceedings is being professionally published. One copy of the Proceedings is included in your paid Conference Registration. (Proceedings are not provided to accompanying family members.) A limited number of additional copies of this year's and previous years' Proceedings will be available at Green Bank for US$20 each. You may, if you wish, reserve and prepay additional Proceedings copies, by including the appropriate amount in your check to our Treasurer. Advance Registration Deadline: Because SARA Conferences require quite a bit of advance planning, early registration is encouraged. To register for the 2014 SARA Conference at the rates cited above, your remittance in full must be received by our Treasurer (not simply postmarked) not later than 31 May, 2014. All registrations received after that date, or walk‐in registrations, will be assessed an additional 15% late registration fee. Payment of Conference Fees: Payment for either OR both conferences can be made by check, money order, PayPal or credit card. Complete the registration form at http://www.radio‐astronomy.org/node/153 and submit with payment. Checks (in US Dollars only, drawn on a US bank) should be sent in advance to: SARA 2189 Redwood Ave Washington, IA 52353 USA
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You can also make payment by going to www.PayPal.com and send money to treasurer@radio‐ astronomy.org. Additional information concerning lodging, directions and information for first time attendees can be found at this link: http://www.radio‐astronomy.org/?q=node/124
Keynote Speaker Announced Vice‐President Tom Crowley is delighted to report that Dr Joe Taylor, K1JT will be our keynote speaker at the Green Bank SARA Conference 29 June ‐ 2 July. A short bio of Dr Taylor follows: Taylor immediately went to the National Radio Astronomy Observatory's telescopes in Green Bank, West Virginia, and participated in the discovery of the first pulsars discovered outside Cambridge. Since then, he has worked on all aspects of pulsar astrophysics. In 1974, Hulse and Taylor discovered the first pulsar in a binary system, named PSR B1913+16 after its position in the sky, during a survey for pulsars at the Arecibo Observatory in Puerto Rico. Although it was not understood at the time, this was also the first of what are now called recycled pulsars: neutron stars that have been spun‐ up to fast spin rates by the transfer of mass onto their surfaces from a companion star. The orbit of this binary system is slowly shrinking as it loses energy because of emission of gravitational radiation, causing its orbital period to speed up slightly. The rate of shrinkage can be precisely predicted from Einstein's General Theory of Relativity, and over a thirty‐year period Taylor and his colleagues have made measurements that match this prediction to much better than one percent accuracy. This was the first confirmation of the existence of gravitational radiation. There are now scores of binary pulsars known, and independent measurements have confirmed Taylor's results. Taylor has used this first binary pulsar to make high‐precision tests of general relativity. Working with his colleague Joel Weisberg, Taylor has used observations of this pulsar to demonstrate the existence of gravitational radiation in the amount and with the properties first predicted by Albert Einstein. He and Hulse shared the Nobel Prize for the discovery of this object. In 1980, he moved to Princeton University, where he was the James S. McDonnell Distinguished University Professor in Physics, having also served for six years as Dean of Faculty. He retired in 2006. Amateur Radio Joe Taylor first obtained his amateur radio license as a teenager, which led him to the field of radio astronomy. Taylor is well known in the field of amateur radio weak signal communication and was assigned the call sign K1JT by the Federal Communications Commission (FCC). He had previously held the call signs K2ITP, WA1LXQ, W1HFV, and VK2BJX (the latter in Australia).[2] His Amateur Radio feats have included mounting an 'expedition' in April 2010 to use the Arecibo Radio Telescope to conduct moonbounce with Amateurs around the world using voice, Morse Code, and digital communications. He wrote several computer programs and communications protocols, including WSJT ("Weak Signal/Joe Taylor"), a software package and protocol suite that utilizes computer‐generated messages in conjunction with radio transceivers to communicate over long distances with other amateur radio operators. WSJT is useful for passing short messages via non‐traditional radio communications methods, such as moonbounce and meteor scatter and other low signal‐to‐noise ratio paths. It is also useful for extremely long‐distance contacts using very low power transmissions. More information on Dr. Taylor can be found at: http://en.wikipedia.org/wiki/Joseph_Hooton_Taylor,_Jr.
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Abstracts‐ 2014 Annual SARA Conference June 29 to July 2 The following papers will be presented at the annual conference at NRAO in Green Bank, WV. Check back for late additions. An Overview of the Radio JOVE Project The Radio Jove Project Team By: Dr. Chuck Higgins Abstract: Radio JOVE is an education and outreach project intended to give students and other interested individuals a hands‐on experience in learning radio astronomy. After selling our first kit in 1999, Radio Jove has sold about 1900 radio telescopes in more than 70 countries around the world. Hardware and software has evolved in this time, and the Radio Jove Team will give a complete update and overview of the status of the program as of 2014. Specifically, we will summarize the latest hardware and software for Radio Jove, include some recent Jupiter and solar observations highlighting the data archive, and discuss some research projects for students. Finally, we will discuss some upcoming projects for Radio Jove and highlight some advanced equipment, software, and results. SETI's New Horizons
by Prof. H. Paul Shuch, N6TX Executive Director Emeritus, The SETI League, Inc. Abstract: The author and his colleagues have proposed to NASA the creation and uploading of a message into the New Horizons spacecraft's memory, following a successful Pluto encounter in 2015. In the tradition of the Voyager Records now traveling through interstellar space, this message will be a self‐portrait of our planet and species, to be shared with all humanity, and potentially with intelligent species elsewhere. The message contents are being crowd‐sourced by people worldwide, and thus represent our planet as a whole. An international board of expert space scientists and engineers has determined this proposal to be technically feasible, and is currently managing all technical details. Programs for K‐12 students will also increase interest in the New Horizons interplanetary probe mission, as well as showing students how they may share in this rare chance to help make a message that will soar among the stars. Production Manufacturing Plan for the RASDR2 Appliance By: Bogdan Vacaluic Authors: Bogdan Vacaliuc, David Fields, Paul Oxley, Stan Kurtz, Carl Lyster, Ricardas Vadoklis and Zydrunas Tamosevicius. Abstract: For the last three years, SARA members have worked to construct a low cost hardware to enable radio astronomy using software defined radio (SDR) techniques. With significant contributions from Lime Microsystems, Ltd. and members of the worldwide community, the team are able to offer to SARA members a high performance receiver appliance specifically tuned for radio frequency measurement. The presentation will describe the appliance, its bill of materials and construction as well as the plan to manufacture and distribute it to radio astronomers and educational institutions. RASDRviewer RASDR2 Control and Analysis Software By: Paul Oxley, David Fields, Stan Kurtz, Steve Berl
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Abstract: The Radio Astronomy Software Defined Receiver (RASDR) is a system that provides a receiver that is optimized for Radio Astronomy. RASDR2 is the current hardware that is in testing with a planned general release at this conference. See multiple other presentations at this conference as well as previous SARA Journals and Proceedings publications for the history of this SARA project. RASDRviewer is the software that controls RASDR2 and presents captured data to the user. It uses a Windows based GUI that is designed for portability to both the Linux and MAC platforms. This portability is mainly based on the use of the wxWidgets development tool that is available as open source freeware. wxWidgets abstracts most of the common graphical window objects to a common language that is applicable across all of the platforms. Thus the look and feel of the user experience is the same regardless of the platform being used. This paper describes the RASDRviewer software and documents some of the experiences in its implementation. A brief discussion of the Windows Driver and FX3 firmware is also included. RASDRviewer is an extension of the Lime Microsystems FFTviewer to optimize radio astronomy functionality. The original FFTviewer presented three charts, I & Q samples vs time, I vs Q for system verification and an output display showing results of a large Fast Fourier Transform (FFT) that operates in near real time. The FFT is capable of delivering up to 16,384 frequency bins multiple times per second. The control of the system required knowledge of the Lime chip architecture and RF engineering theory. For RASDRviewer, modifications have been made to customize the software for Radio Astronomy use. This includes optimization of control functions for radio astronomy use, addition of a Power vs Time plot, file outputs and inclusion of a simplified selection of the user options. In addition, RASDRviewer makes full use of the receive capabilities of the Lime Chip including sample rates up to 32 M Samples / Second and 28 MHz of bandwidth. RASDRviewer is being demonstrated at this conference. The demonstration will include real‐ time control of RASDR2 to produce three dimensional FFT plots. A copy of the software executable is included in the CD for this meeting. Measuring the Field Strengths of VLF Stations By: Tom Hagen Abstract: This presentation is about an attempt to get calibrated measurements of the magnetic field strengths of the various VLF stations used by the SuperSID program as reference sources to detect sudden ionospheric disturbances (SID’s). Presently, data coming in from the various SuperSID stations around the world is uncalibrated in amplitude. When a SID is detected, there is a measurable change in relative signal strength, but actual field strengths are unknown. Different stations around the world report different SID levels for a given event. Are the causes of these differences loop antennas, preamp gains, sound card settings, sound card gain, or actual differences in field strength levels? And for better system design, the typical range of field strengths would be good to know for improving and standardizing the design of pre‐ amps and loop antennas. Finally, a mathematical model is developed and verified for the Helmholtz Coil that was used for test setup calibration. 611 MHz Total Power Radio Telescope‐Part 0x02 By: Ken Redcap Abstract: Part 0x01 of this presentation was given at the SARA 2014 West Conference. Part 0x02 will focus on analyzing the results from an 8‐Bay bowtie TV receive antenna, configuring/tuning the C# program SDRSharp.exe, investigating available software plugins for SDR# and testing a second (yagi) antenna. This project is a work in progress and is my first effort on a radio telescope to detect energy in this frequency range. The telescope is being set up at the McMath Hulbert Solar Observatory (MHO) in Lake Angelus, MI. All electronic components and antennas (3) required were purchased from Amazon except for the low noise
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amplifier. All freeware software components were derived from sites with various versions of SDR# like SDRSharp.Com. Inspiration for the project comes from Kurt Kinghorn's presentation at the 2013 SARA Western Conference on low cost radio telescopes using off‐ the‐shelf TV receive antennas and an article in the August, 2013 SARA Journal about a low cost HI receiver. Microwave Antenna Demonstrations By: Jon Wallace Abstract: The presenter has had a fascination with non‐visual astronomy for over 25 years and has developed and built devices to share this with students and other teachers. After seeing a video of John Kraus giving a demonstration on radio antennas many years ago to the IEEE, the presenter was so inspired that he sought to reproduce as much of it as he could. Many of the ideas were unknown to the presenter and a couple were thought provoking and required exploration. It is hoped that these demonstrations will educate and inspire others to explore as well. The equipment consists of a Gunn diode source with horn antenna and a horn antenna with crystal detector, instrumentation amplifier, and VCO so that changes in intensity will be heard as pitch changes. The demonstrations cover topics which include: beam width, inverse square law, polarization, reflection, refraction, interference, absorption, gain, wave guides, and more. VSRT Radio Demonstration By: Jon Wallace Abstract: After working with the new radio astronomer at Wesleyan University, Meredith Hughes, building the SRT and VSRT, the presenter experimented with the VSRT himself. The VSRT was designed primarily by Alan Rogers of Haystack Observatory in Massachusetts. We visited him and tested equipment and were able to come away with some real insight into the Haystack teaching radio telescopes. The presenter hopes to demonstrate the VSRT and show some of the activities it can do. It is a wonderful way to explore interferometry in a classroom and perhaps beyond. An Introduction to Black Body Radiation By: Tom Crowley Abstract: This is an introduction to Black body Radiation and its importance to radio astronomy. The discussion will relate temperature to Electro‐magnetic Radiation and how to compute what the frequency based on temperature and vice versa. Radio Astronomy with RASDR2 Authors: D. Fields, P. Oxley, B. Vacaliuc, S. Kurtz, C. Lyster, Z. Tamosevicius, C. Sufitchi and S. Berl By: David Fields Abstract: The RASDR design team is releasing an initial version of a software‐defined receiver (SDR) for radio astronomy entitled RASDR2. The receiver consists of two high‐density circuit boards ‐‐ a wide‐band femtocell chip on the front end analog interface MyriadRF board linked to a digitization and function control DigiRed board ‐‐ coupled to a computer via a USB3 interface. RASDRViewer software runs in a Windows environment and performs receiver control, FFT analysis, spectrum averaging, power monitoring and other functions. Depending on specific application, RASDR2 is used with an antenna, filter, preamplifier, optional upconversion or system control devices, and external frequency/time reference signals. The team has three RASDR2 units in operation and is working to make units available to SARA members.
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RASDR2 software, firmware and hardware are discussed in other conference presentations. This presentation covers RASDR2 application to solve some common experimental challenges encountered by members of the community of amateur radio astronomers. Results of operation in several RF spectral bands will be shown and discussed. SID Monitoring using Raspberry Pi By: Ciprian “Chip” Sufitchi Abstract:As technology advances and becomes more and more affordable, research/crowdsourcing projects such as Sudden Ionospheric Disturbance (SID) monitoring could run 24 hours a day on inexpensive devices. Traditionally, a computer (PC) equipped with a good quality sound card is required to receive VLF signals, process them, store and draw data, and report it in a public database. For a continuos operation a PC is not an ideal platform though, being unreliable and expensive. Attempts to use microcontrollers such as Arduino were successfull, as presented at the Annual SARA Conference in 2013 (“Sidruino”) however they generally require an external VLF receiver. Raspberry Pi, a credit‐card‐sized single‐board computer developed in the UK by the Raspberry Pi Foundation based on Linux as operating system, could be an attractive alternative – it is inexpensive, fast enough to perform Fast Fourier transform on incoming audio signal from the audio board, can be powered from batteries and it is supported by a large group of open‐source enthusiasts around the world. The paper will focus on external hardware able to receive a wide VLF spectrum and a few SID monitoring applications running on Raspberry Pi. The role of mass produced antennas and feeds on the future of radio astronomy development "A Survey" By: Mohammed Q. Hassan Abstract: The rapid development in modern radio astronomy has led to proposing low cost high production level antennas. While the Allen Telescope array is dependent on 21 ft. offset Gregorian antennas having 42 antennas and the potential of increasing it to the full array of 350 units depending on funding, there is a far more profound project that is better financed internationally with a potential of having 3000 antennas, which is the Square Kilometer Array (SKA). The SKA will have similar offset Gregorian antenna design except that the antennas will be considerably larger (49 ft. or 15m in diameter), providing lower frequency start‐up and ending range from its log periodic feeds. Such a single antenna configuration can make it attractive for university based educational radio astronomy projects, where simultaneous observations over a number of frequencies within the specified range can be made possible. This review / survey paper will show us the challenges put forward to combine several ground breaking concepts leading to a unified design that could be produced in large numbers. Several institutions are collaborating to bring this into fruition.
Tentative 2014 SARA Conference Schedule Sunday 29 June‐ Wednesday 2 July, 2014
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Day
Time
Speaker
Title
Sunday
12:00 PM
Melinda Lord
Registration at NRAO Dorms
29 June
12:30 PM
Tom Hagen
Radio Astronomy Beginner Session
3:00 PM
Tom Crowley
40 FT Radio Telescope Workshop
5:15 PM
Dinner NRAO Cafeteria
6:30 PM
Set Up Outside Experiments
Sunday
8:00 PM
Social at Drake Lounge
Monday
7:15 AM
Lynn Crowley
Ladies meet in residents dorm lobby for car pool to Greenbrier for Breakfast
30 June
7:45 AM
Breakfast in NRAO Cafeteria
9:00 AM
Tom Crowley, VP
Introductions and Opening Remarks
9:15 AM
Bill Lord, President
SARA Announcements
9:45 AM
Jon Wallace
Microwave antenna demonstration
10:15 AM
Coffee Break and Poster Session
10:30 AM
David Fields
Radio Astronomy with RASDR2
Paul Oxley
RASDR2 Control and Analysis Software
Bogdan Vacaluic
Production Manufacturing for the RASDR2
12:30 PM
Lunch NRAO Cafeteria
1:30 PM
Bill Lord
Call for Nominations
2:00 PM
Paul Shuch
SETI New Horizons
2:40 PM
Coffee Break and Poster Session
2:55 PM
NRAO
Science Update
3:40 PM
Tom Hagen
Measuring the Field Strengths of VLF Stations
4:10 PM
Jon Wallace
VSRT Demonstration
4:45PM
Tom Crowley
Black Body Radiation
5:15 PM
Dinner at the NRAO Cafeteria
6:15PM
Flea Market in Dorm Parking Lot
6:15 PM
Setup Outside Experiments
7:00 PM
SARA Board of Directors Meeting
Monday
8:00 PM
Social at Drake Lounge
Tuesday
7:45 AM
Breakfast at NRAO Cafeteria
1 July
9:00 AM
Bill Lord
Elections
9:30 AM
Bill Lord
Business Meeting
10:00 AM
Coffee Break and Poster Session
10:15 AM
Joe Taylor
Key Note Speaker
11:15AM
Chip Sufitichi
SID Monitoring using Raspberry Pi
11:50 AM
Ken Redcap
611 MHz Total Power Radio Telescope
12:00 PM
Lynn Crowley
Ladies meet in residents dorm lobby for car
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pool to Cass Railway
12:30 PM
Lunch NRAO Cafeteria
1:30 PM
Group Picture
1:45 PM
Sue Ann Heatherly
NRAO High‐Tech Tour
3:15 PM
Snack Break and Poster Session
3:30 PM
Mohammed Hassan
The Role of Mass Produced Antennas and feeds on the future of Radio Astronomy Development
4:15 PM
Chuck Higgins
An Overview of the Radio Jove Project
5:00 PM
Tom Crowley
2014 Conference Plans
5:15 PM
Dinner at NRAO Cafeteria
6:15 PM
Setup outside experiments
Tuesday
8:00 PM
Social in Drake Lounge
Wednesday 7:45 AM
Breakfast in NRAO Cafeteria
2 July
9:00 AM
Conference Ends
9:00 AM
Radio Jove Conference Begins
Ladies Outings at SARA Annual Conference Preliminary Schedule Monday, June 30
7:15 AM ‐ Meet in the Residents Dorm Lobby to car pool
9:00 AM ‐ Breakfast at the Greenbrier Hotel's main dining room “Breakfast is a gracious and traditional affair featuring regional signatures, American favorites, and delicious healthy options served a la carte and buffet style. Breakfast prices are not longer posted on the Greenbrier's web site. In 2012 menu items were from $4 to $14 a la carte, and the Breakfast Buffet was $23.
10:30 AM ‐ Interior Tour of the Greenbrier Hotel
11:30 AM – Explore the hotel or shopping in White Sulphur Springs
3:00 PM‐ish – Return to Greenbank
Tuesday, July 1
AM (Time TBD) ‐ Meet in the Residents Dorm Lobby to car pool
12:00 Noon ‐ Cass Scenic Railroad 4 ½ hour trip to Bald Knob, the third highest point in West Virginia. The overlook at Bald Knob provides a spectacular view at an altitude of 4,700 feet and the National Radio Astronomy Observatory can be seen from the overlook. Adult ticket is $25.
4:30 PM – Return to Greenbank For questions contact Lynn Crowley ‐ cell 404.683.7948 or e‐mail
[email protected]
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SARA Annual Conference Door Prizes Watch for more door prizes in the next Journal. Radio Astronomy Supplies will be donating a SpectraCyber receiver as a door prize at this year’s meeting in Green Bank. This unit is contained in a 12” table top cabinet instead of the usual rack mount chassis. If all goes well with antenna transportation this unit will be demonstrated at the grassy area behind the dorm during the conference. The winner will need to supply a feedhorn and preamp as well as an antenna to complete the station. The value of this prize is estimated at $1500. At right‐ is data recorded by the SpectraCyber unit. SARA is donating a SuperSID system complete with antenna wire and coax. Value $85.00 HP3576 Selective Level Meter with 32 MHz bandwidth, can be used as a signal generator, comes with manual, donated by Bill Lord Microdyne Model 1100‐TVR(X24)B2 Receiver 3.7 to 4.2 GHz New in Box with original manual, donated by Ed Harris of Lincolnwood, Illinois Books‐ “The Elegant Universe” by Brian Greene and “Atlas of the Skies” donated by Bill Lord DataQ A to D converter with serial port donated by the SARA SuperSID Project
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Officer and Director Nominations Ballots for members not attending will be in the next Journal.
President Nominated for President‐ Ken Redcap I am Ken Redcap and would be excited to serve as president of SARA. I live in Rochester, MI and also spend time in Charlottesville, VA (which happens to be the home of NRAO). My call sign is KD8WOA as of this last February (at HAMcation). I have a BSEE, BSCh and an MSEE and am currently employed as an industrial engineer.
I am also a member of the McMath Hulbert Astronomical Society along with Tom Hagen. We are currently setting up an "Off‐The‐Shelf 611 MHz Total Power Telescope" on site at the McMath Hulbert Solar Observatory ‐ which has been inspired by Curt Kinghorn. This is a very exciting time for SARA with the availability of low cost hardware and software components ‐ and along with other members of SARA I use these components to spread the word about radio astronomy both at home and in the class room.
Vice‐President Nominated for Vice‐ President‐ Tom Hagen, I'd be honored to serve as SARA Vice President and to continue the fine work of the past officers and appointees. My vision for SARA is continued growth of the organization. There are several areas where I feel I could contribute: ‐Make the hobby more accessible to first time radio astronomers by promoting the development of simple radio telescopes based on the recent availability of inexpensive SDR dongles and freeware ‐Organize annual conferences with fun and interesting activities, presentations, and keynote speakers ‐Work with the SARA leadership as a team player to achieve larger organizational goals My background is in electrical engineering, with a Master's degree; I live and work in the Detroit area with my wife and 3 cats.
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Secretary (One year term position vacated by Tom Hagen) Nominated for Secretary‐ Bruce Randall, Hello I’m Bruce Randall and live in Rock Hill S.C. I was born in 1949, so am getting to be an old timer. My first ham radio license was in 1966. Presently I have an extra class license with the call of NT4RT. (The RT in the call is for “Radio Telescope.”) Ham radio and optical astronomy led to my interest in radio astronomy. I Retired September 2013. I had been an electronic engineer since 1978, with involvement in analog circuit design, power supplies, electromagnetic compatibility, a bit of DSP work and some antenna design. My hobbies include old British cars, astronomy, ham radio and radio astronomy. I also enjoy canoeing, hiking and camping, as time permits. I have been a SARA member for over 20 years and am now a life member. Experiments with radio astronomy started in 1990, in the days of the chart recorder as the output device. The present interested is interferometers and possible extended baselines in the future. I have been on the SARA board in the past and would like to serve SARA as secretary.
Director (Two year term) Two Open Positions Director (One year term position vacated by Ken Redcap) Nominated for Director‐ Stephen Tzikas Steve Tzikas is a recent newcomer to SARA, joining in 2013 and attending his first SARA conference the same year. He has been interested in astronomy since childhood. He has a MAppSc in Chemical Engineering and Industrial Chemistry from UNSW in Australia, and a BS in Chemical Engineering from Rensselaer Polytechnic Institute in NY. He is also a member of the Northern Virginia Astronomy Club (NOVAC), ALPO, and the Rensselaer Astrophysical Society (RAS). He is currently a Management Analyst / Computer Modeler for the Department of Homeland Security, and has 30 years of experience in government and the private sector. His early career was focused on environmental engineering. Steve’s many personal interests include travel, genealogy, philosophy, art, and classical music.
Steve’s goals for the future of SARA is to make it more amenable to interest segmentation and participation. This includes establishing: Radio Astronomy sections within SARA A cataloged archive of list‐serv information Correspondence tools for local astronomy club / park partnerships in urban / suburban locations where large yards conducive to radio astronomy observation might not be common. An observing certificate program
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Nominated for Director‐ Carl Lyster Carl is one of the original founders of SARA at #18 on the roster. He has previously held a position on the board of directors and is a regular at the Green Bank meeting. He is in his 36th year at the Y‐12 National Security Complex where he is employed as an Engineer in the Analytical Chemistry Lab. Carl is the creator of the Spectracyber hydrogen line spectrometer which is the culmination of a life’s work since age 14. (This is a funny story, ask him about it sometime)! He is an avid electronics enthusiasts and Amateur Radio Operator since 1972. Definitely one of the old Analog guys! Nominated for Director: Jim Brown NJ3B Jim Brown has been an active SARA member since 1999 and currently serves on the Grant Committee. As Mentor Chairperson, Jim compiled a computer disk full of radio astronomy resources to support the mentors in their outreach. Jim has served on the board of directors. Jim is an avid Radio Jove observer and provides mentoring to new RJ observers on calibrating and other topics. Nominated for Director‐ Preston Ozmar Preston Ozmar received his Bachelor of Science and Master of Science degrees from Virginia Tech in 1969 and 1976, both in Electrical Engineering. Preston serves as an adjunct science instructor at Wave Leadership College in Virginia Beach, VA. He worked 10 years at Virginia Tech in Blacksburg, VA as a Television Systems Engineer and 28 years at CBN as a Senior Network Design Engineer. Preston’s call sign is WB4GQD and he has an advanced class amateur radio license. In addition to SARA, Preston is a member of the Institute of Electrical and Electronic Engineers and the Optical Society of America, a society of the American Institute of Physics. Preston enjoys using his Jove receiver and being a part of SARA.
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Director‐At‐Large (Two year term) Two Open Positions Nominated for Director‐At‐Large: Keith Payea Keith was born at the beginning of the space race, and was fascinated with science from an early age. A crystal radio kit and a department store telescope were early Christmas gifts. He won a Bausch and Lomb Science award in High School and went on to earn a BSEE from Worcester Polytechnic Institute in 1979. As a freshman at WPI, Keith received his first amateur radio license. After a 24 year career as an engineer, project manager, and department manager, he decided to become a full‐time consultant in 2003. A flier on the wall at work in 2000 introduced Keith to the Robert Ferguson Observatory (RFO) in Kenwood, CA. He quickly signed on as a docent and became very involved in the local amateur astronomy community. For two years, Keith was President of the Sonoma County Astronomical Society. In parallel he had discovered the online presence of SARA and the SETI League and joined both. For the last few years his primary activity at the RFO has been to interpret Radio Astronomy for the visitors using a donated Radio Jove receiver in the context of general solar observing. A long term goal is to have 24/7, remotely accessible radio observations at the RFO. In early 2011 Keith took all three tests in one sitting and earned his Extra Class license, AG6CI. He is also active in the local ham radio club and enjoys operating “Field Day” style at parks and campgrounds. Keith has been an attendee and sometimes presenter at four of the SARA Western Conferences so far. High on his “Bucket List” is to attend the SARA annual conference and meet some of the folks he has only known on‐line. Keith lives in Santa Rosa, CA with his wife Nicolette and a cat named Luna. Nominated for Director‐At‐Large: David Westman David Westman lives in Seattle, WA. He is a retired software engineer, and he was born in 1944. He majored in Physics/Astronomy at Pomona College in Claremont, CA, graduating in 1966. Since this was the middle of the Vietnam War troop buildup, he elected to join the Air Force rather than be drafted into the Army. After his Air Force service was over, he worked for several years as a technical editor, and then took some more classes to become a computer programmer. After a few years, he landed a job at Boeing in Seattle, and they paid his way to earn a degree in Computer Science. He worked at Boeing for 26 years, retiring in 2005. After he retired from Boeing, he resumed his interest in astronomy and renewed his study of radio astronomy. He earned a Masters of Astronomy from James Cook University in Australia over the internet, and has audited many classes in astronomy and physics at the University of Washington in Seattle. He has
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also taken a radio astronomy course over the internet from Jodrell Bank Observatory in Manchester, UK. He eagerly keeps up with the latest scientific research, and regularly meets with faculty members at the UW to deepen his understanding of these topics. He has taken part in research on QSO variability and large scale survey variable star identification, and hopes to carry on useful work in radio astronomy for many more years. He is married and has two grown sons; one works as a fisheries biologist, and the other is a junior manager at a company selling vinyl cutting equipment. Nominated for Director‐At‐Large: Dave James
Inspired by the British amateur Frank Hyde, whom he never met, Dave built a simple VHF radio telescope when at high school in England, but only returned to the subject ‐ as an amateur again ‐ a couple of years ago in retirement. He originally worked in R & D for space systems in Canada, and later worked for companies that included Ferranti, Nortel, Racal, ArrayComm. He was also a consultant, visiting UMIST lecturer, and also founded a company specialising in solid‐state combinatorial power amplifiers. Much of his working life was spent in managing R & D in microwave technology, but he also worked on low‐loss ceramics, high‐vacuum technology and hi‐rel packaging. At one point he built parametric and transistor amplifiers for radio astronomers and subsystems for data links for the original MERLIN. The main systems he was involved in were civil and military satcom, radar, EW, missile, telecomm and cellular mobile. He also worked in CEPT, CITEL and ITU‐R on spectrum regulation and in the IEEE, ETSI and TIA on international microwave system standards. Dave recently became a licensed amateur radio ham. He built an optical observatory in his garden a couple of years ago, and is now building up a radio astronomy and geophysics observatory at a quiet rural location near his home in S West England. He now edits the BAA’s new RAGazine, and also has an interest in social insects.
Radio Jove Conference Jim Thieman The JOVE Team, together with the Society of Amateur Radio Astronomers (SARA), is pleased to announce a joint meeting this summer at the National Radio Astronomy Observatory in Green Bank, WV. This meeting will take place from Sunday June 29 through the morning of Friday July 4, 2014. The SARA part of the meeting will start Sunday with an introduction to Radio Astronomy at the Science Center classroom, followed by learning to operate the forty foot radio telescope (1,420 MHz ‐ 21 cm). Presentations by SARA members and guests will be given on Monday and Tuesday. A High Tech tour of the NRAO facility will be conducted on Tuesday 1 July. The JOVE meeting will occur Wednesday and Thursday with talks ranging from entry level descriptions of Jove hardware and software to more advanced measurement techniques and science of the Jovian emission sources.
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Attendees may register for either the SARA segment or the JOVE segment of the meeting, or both. Registration details may be found on the SARA website http://radio‐astronomy.org/meetings. Contact Melinda or Bill Lord (
[email protected]) if you have questions about the logistics. Contact Jim Thieman (
[email protected]) if you have questions about the Radio Jove meeting agenda.
An overview of the Radio Jove portion of the 2014 SARA/JOVE summer meeting The Jove meeting begins on Wednesday morning with a discussion of the Jove radio telescope. Throughout the day we will progress from the basics of radio Jove to more advanced systems. Along with discussions of receiver hardware and analysis software, you will hear about Jovian emissions, the source of these signals, and remaining mysteries as to how these signals are generated. Beginning at an introductory level suitable for the new Jove observer, we will progress to advanced receiving systems and analysis being performed by amateur and professional Jupiter radio astronomers. On Wednesday morning, Dr. Jim Thieman will begin with an overview of the Jove program. Wes Greenman and Dick Flagg will describe the Jove radio telescope performance in terms of noise figure, dynamic range, gain and frequency stability, antenna beaming pattern, phasing, sensitivity and calibration. Jim Sky will reveal little known secrets of the ever‐popular SkyPipe and Radio Jupiter Pro software. You will learn about the Jove data archive and new initiatives to share data with global virtual observatories. Dr. Chuck Higgins will give the first of two talks focusing on Jupiter science, describing what has been learned using equipment similar to the Jove radio telescope. Chuck will tell us about the source regions, the Io effect, the radio rotation period of Jupiter, emission spectrum and more. On Wednesday afternoon, Dick Flagg, Dave Typinski, and Jim Sky will describe more advanced receiving hardware and software systems including spectrographs (analog and digital), polarimeters, and wideband antennas. You will learn more about the various forms of Jovian emissions: S‐bursts, L‐bursts, N‐events and modulation lanes as well as propagation effects occurring in the interplanetary medium and earth’s ionosphere. Jupiter’s dynamic radio spectrum as viewed over a time scale varying from hours to a few hundred microseconds will be revealed. Following Dave Typinski’s mind‐numbing tutorial on the fast Fourier transform, we will take a virtual tour of his observatory including a dual polarization spectrograph, a new tuneable wideband receiver and Dave’s wideband, dual polarization, beam steering antenna array. The afternoon will wrap up with a presentation about the recent exploits of the SUG (a spectrograph users group). The Thursday sessions begin with an extension of Jupiter radio science from the day before, and then the talks focus on results gathered with both amateur and professional radio telescopes. Dr. Kazumasa Imai will speak about the Japanese Agawa Radio Observatory. We’ll also have Stan Kurtz from UNAM, Mexico, discussing how Radio Jove is used there for research and education. Other research talks from longtime Radio Jove observers include N‐events, accurate timing systems, the SL‐9 comet encounter with Jupiter, new
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observations made with the Long Wavelength Array (LWA), and some solar radio science. The meeting concludes with an overview of the Juno mission to Jupiter and the future of the Radio Jove program. In addition to the daytime talks, we plan to have the Jove radio telescope and additional equipment set up on the field most evenings. Join us for some hands‐on, one‐on‐one discussions, both there and in the Drake Lounge.
Tentative Radio Jove Meeting Schedule Wednesday July 2, 2014 ‐‐‐ Radio Jove Hardware and Software Basics + Advanced Systems Time Speaker Topic 7:45 am Breakfast Breakfast in the NRAO Cafeteria 8:45 am J. Thieman Welcome and Radio Jove Meeting Overview 9:15 am R. Flagg, Radio Jove Hardware – Receiver and Antenna W. Greenman 9:45 am J. Sky Radio‐Skypipe 101 10:15 am R. Flagg Calibration 10:30 am Break 10:45 am RJ Team Archiving Data 11:00 am C. Higgins Introduction to Jupiter Science 11:30 am J. Sky Radio Jupiter Pro (RJP) Software 12:15 pm Lunch Lunch in the NRAO Cafeteria 1:30 pm R. Flagg Introduction to Advanced Measurements Systems 2:15 pm R. Flagg, D. Typinski, Basic Spectrograph Hardware and Software J. Sky 2:45 pm D. Typinski The Fast Fourier Transform (Tutorial) 3:15 pm Break 3:30 pm R. Flagg, D. Typinski The Tunable, Wideband Receiver (TWB) 4:00 pm D. Typinski Polarization, Beam Steering, Dual Polarization Spectrograph 4:30 pm R. Flagg Spectrograph User’s Group 5:00 pm Dinner Dinner in the NRAO Cafeteria 6:30 pm All Hands‐On Radio Astronomy on the Lawn 7:30 pm All Drake Lounge Open for Discussions and Social Thursday July 3, 2014 ‐‐‐ Science and Radio Jove Future Time Speaker Topic 7:45 am Breakfast Breakfast in the NRAO Cafeteria 9:00 am J. Thieman, Advanced Jupiter Science Summary C. Higgins 9:30 am K. Imai, T. Ohno Status of the Agawa Radio Observatory, Kochi, JAPAN 10:00 am J. Brown Jupiter Narrow Band (N)‐Events 10:30 am Break 10:45 am A. Mount Precision Time by GPS 11:15 am C. Higgins The Long Wavelength Array (LWA) – Jupiter Results 11:45 am F. Reyes Low Frequency Observations of the SL‐9 Impact with Jupiter 12:15 pm Lunch Lunch in the NRAO Cafeteria 1:30 pm S. Kurtz Team Mexico and Radio Jove 2:00 pm RJ Team (tentative) Large Groups using Radio Jove for Education (tentative) 2:30 pm RJ Team Solar Science
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3:00 pm 3:45 pm 4:15 pm 5:15 pm 6:30 pm 7:30 pm
Break RJ Team J. Thieman + RJ Team Dinner All All
Friday 7‐04‐14 ‐‐‐ Departure Time Speaker 7:45 am Continental Breakfast 9:00 am
The Juno Mission 2015‐2017 and Radio Jove Observing The Future of Radio Jove Dinner in the NRAO Cafeteria Hands‐On Radio Astronomy on the Lawn Drake Lounge Open for Discussions and Social
Topic Continental Breakfast in the Drake Lounge [NRAO Cafeteria is closed for the holiday] Departure
Cartoon by Nick D Kim. Strange‐Matter.net Used by permission
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SARA at Claremore, Oklahoma Hamfest Robert Tucker represented SARA at a booth at the Claremore, Oklahoma Hamfest March 7 and 8. This is the second year Robert has set up a display for SARA promoting radio astronomy.
Above‐ Robert’s wife, Marcia at the SARA display. Robert had an iPad with pictures from the 2013 Western Conference held at the Very Long Array (VLA) at Socorro, New Mexico.
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Summary of 2014 SARA Western Conference ~ Bishop, California Julian Jove The 2014 SARA Western Conference was held in Bishop, California USA over the weekend of 22~23 March at the Owens Valley Radio Observatory (OVRO) and Holiday Inn Express. Bill and Melinda Lord again worked hard to get everything setup, and David Westman helped arrange our visit to the OVRO, which is about 27 road miles south of Bishop . Whitham Reeve, conference coordinator, did very little but, of course, took all the credit as we have come to expect. We had 30± attendees at this year’s conference, and to my knowledge there were no trouble‐makers in the group except, as usual, SARA president Bill Lord. The format for this conference included presentations by SARA members and outside speakers and tours of the radio telescopes and laboratory facilities and shops at the main OVRO site in Owens Valley and the CARMA (Combined Array for Research in Millimeter‐Wave Astronomy) site in the mountains east of OVRO. Our morning session on Saturday was at Building 12 on the main site and included opening remarks by the president, an introductory astronomy presentation by SARA member and director Tom Hagen, and presentations by two speakers from OVRO, Stephen Muchovej and David Hawkins. We then toured the aforementioned sites with Mark Hodges (Design Engineer) leading us for the OVRO tour and Nikolaus Volgenau (Assistant Director of Operations) leading our tour of CARMA about 15 road miles from OVRO. Pictured: Left‐to‐right, Front: Tom Hagen, Eric Minassian, Stephen Muchovej, Ken Redcap, Scotty Butler, Jerry Espada, Whitham Reeve. Next row: Virginia Weisz, Karoline Abedi, Ray Fobes, Robert Tucker, Karen Nelson, Lorraine Rumley, Stuart Rumley, Lynne Gose, Jeff Gose, Karin Arnold, Fred Miles, Wolfgang Arnold. Back row: Bill Lord, Mark Hodges, Jim Moravec, Keith Weisz, Richard Rynne, Nikolaus Volgenau, David Hawkins, Tom Butler, Curt Kinghorn, Stan Nelson, Keith Payea, John Roberts, JR Van Hise. Not pictured: Melinda Lord
We finished our tours of the OVRO and CARMA sites early Saturday evening and had our group dinner at Astorga’s Mexican Restaurant just outside Bishop on the North Sierra Highway (Highway 395). Astorga’s is the only restaurant in town that could accommodate 30 people in one group on Saturday night. This worked out quite well. We ate no end of chips and salsa and then had various Mexican dishes and drinks. Another restaurant we found in Bishop that has great food and drink is the Back Alley – the restaurant in the local bowling alley. The service there was excellent, and it actually is in the back alley behind our hotels. We continued our conference on Sunday morning in the “conference room” at the Holiday Inn Express in downtown Bishop, across the street from SARA’s official hotel the Creekside Inn. The management of this Holiday Inn Express must have been on vacation. On our arrival we were told by the front desk “nobody left us a note or anything about this”. Melinda Lord, SARA Treasurer, had previously made arrangements for the conference room but it was not setup for us and nobody there knew we were coming. Furthermore, it was much smaller than we were led to believe. It had three or four chairs, a table and a projection screen. Melinda quickly took charge and grabbed a wrecking bar and industrial size reciprocating saw. In no time we robbed the hotel’s dining area and every loose chair we could find and by 9:00 AM had 30 chairs setup in the room. One of the hotel’s maintenance staff was very helpful, but he was the only one in the whole Holiday
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Inn Express Empire who could not care less about our previous arrangements. As it turned out we made out okay and we were treated to numerous technical presentations by SARA members and directors (see the schedule of presentations at http://www.radio‐astronomy.org/node/160 and their abstracts at http://www.radio‐astronomy.org/node/). Wolfgang Arnold manned the air conditioning controls – we needed the refrigeration unit to cool the room with 30 people that was designed for 10. Satellite Images of the Sites Owens Valley is approximately 250 miles north of Los Angeles on the east side of the Sierra Nevada Mountains not far from nowhere. The image below is for 30 km altitude and shows the city of Bishop in upper‐left, the main OVRO site in lower‐middle and the CARMA site at middle‐right. A scale bar is in the lower‐left. The main site is about 11 airline miles to the south and east of Bishop but the drive is closer to 27 miles. See satellite image from 3 km altitude below. The CARMA site is another 9 airline miles from OVRO but requires driving about 15 miles into the mountains on a narrow, wandering road. A satellite image from 3 km altitude also is shown below. Owens Valley from 30 km altitude
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OVRO from 3 km altitude
LWA
NRAO Telescope
Solar Array
Building 12
40 m Telescope
CARMA from 3 km altitude
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Photo Tour of Owens Valley Radio Observatory
Above: Building 12 on the OVRO site where we had presentations on Saturday morning in a comfortable conference room. The building is conveniently located near the 40 m radio telescope shown below.
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The 40 m telescope rests on railroad trucks and rails but the rails go nowhere. It apparently was originally designed to be part of a moveable array that was never funded. The railroad tracks are massive.
A complete photo tour of OVRA and CARMA can be seen at http://www.radio‐astronomy.org/node/169
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Radio Astronomy Receivers Bruce Randall, WD4JQV
Nature of Radio Astronomy Signals Radio Astronomy signals are generally of a random nature. The random motion of atoms causes electrical noise. Thermal, synchrotron, and spectral line signals are all random signals. (Spectral lines do have a random component.) These random nature signals have significant influence on the design of radio astronomy receivers. The exception to random signals might be a SETI signal, if and when it is found. Our signals are noise to other radio users! The receiver design rules are a bit different from a communications receiver. Most radio astronomy receivers are classified as radiometers. A radiometer is a device that measures the temperature of an object from the electromagnetic radiation given off by the object. In our case the electromagnetic radiation is radio waves. See Figure 1. There is an actual flow of power from the hot object to the power meter via the radio waves and antenna. The measurements from a radiometer are normally given in terms of temperature. The temperature is usually expressed as degrees above absolute zero or Kelvin (K). Even when the electromagnetic radiation is due to some mechanism other than physical temperature, it is normally expressed as an equivalent temperature. Because our signal is random noise, the power meter will have an averaging mechanism to get a stable reading.
In radio astronomy, our hot object does not normally fill the view of the antenna, see Figure 2.
This results in the measured temperature being lower than the actual temperature of the object. If we can not resolve the object with the antenna, we do not know the true temperature. By 10% of the field of view we mean 10% of the area as viewed by the antenna.
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If the object is smaller and hotter it can result in the same receiver input temperature as shown in Figure 3. The receiver sees the average temperature over its field of view.
Expressing the signal as a flux density in units of Janskys takes care of this for the radio telescope. The receiver itself will be characterized in measured temperatures. If the angular size of the object is known, its approximate physical temperature can be calculated from the flux density. Note that the flux density measurement includes antenna area, so indirectly, field of view. Flux density is independent of the radio telescope.
Total Power Receiver Figure 4 shows a block diagram of a total power receiver. It consists of bandpass filters (BPF) to select a range of signal frequencies, an amplifier to bring these very weak signals up to a measurable power level, and a power meter. TA is the received signal from the antenna. TN is the undesired noise generated by the amplifier. TN is often much larger than TA. The power measured is defined by the laws of physics as:
P = k ⋅T⋅ B P is the power in watts. k is Boltzmann’s constant. 1.38 × 10‐23 T is the absolute temperature in Kelvin. It is the sum of TA + TN. B is the receiver bandwidth in Hertz.
Because k is extremely small, the power level to the receiver is extremely small. The amplifier has extremely high power gain to produce a measurable power level. As a practical matter, at least two bandpass filters are needed. The first is between the antenna and the amplifier to protect the amplifier from interference outside the frequency band of interest. A second filter is needed between the amplifier and power meter because any real amplifier generates noise power, both inside and outside the band of interest. The amplifier noise power in the band of interest is added to our sky
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measurement. The noise power that is outside the band of interest is removed by the second filter. A typical receiver is a superhetrodyne, which has many filters and amplifiers. The power detector produces an output voltage that is proportional to the input power. The input power is proportional to input voltage squared, so the detector needs to be a “square law” detector. Kraus [1] on pages 7‐9 and 7‐10 points out the need for square law detection for both best sensitivity and ease of telescope calibration. Logarithmic power detectors, such as the Analog Devices AD8307 have been used in radio telescope projects with some success. The log power detector does limit sensitivity, but gives a very large dynamic range that is needed for work such as solar flares. The average function is shown outside the main receiver block, because it is handled differently in more advanced receivers. This function is labeled as an integrator in most references. Mathematically it is a low pass filter and not an integrator! I have seen failed amateur radio telescopes because someone used an analog integrator from an op amp design book where a low pass filter was needed. Radio telescope sensitivity is the smallest temperature change that can be seen in the random noise of the receiver output. The sensitivity of a total power receiver is defined as: ΔT =
T A + TN B ⋅τ
ΔT is the minimum detectable temperature change of a receiver TA is antenna temperature. This is the temperature of what the antenna sees. TN is the noise temperature of a receiver or amplifier. B is the bandwidth of receiver in Hz τ is the receiver averaging time constant in Seconds. In a communications receiver the best bandwidth is just large enough to pass the information in the signal. In a radio telescope, larger bandwidth yields better sensitivity. Remember our signal is noise. For the sake of illustration, typical values will be assigned to the sensitivity formula: TA = 50K TN = 100K B = 1 × 106 Hz or 1MHz τ = 20 Seconds
ΔT =
50 K + 100 K 10 6 Hz ⋅ 20 S
= 0.034 K
Note that a 0.034K change out of 150K is only about 0.02%. The small change is the signal of interest. It is desired to remove the effects of temperatures not caused by the radio source of interest. This leads into the next receiver type. Examples of the total power receiver are discussed in reference [2].
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Total Power Receiver with Offset. Subtracting an offset voltage from the output of a total power receiver allows making better use of the receiver’s sensitivity. See figure 5. VBAL will be adjusted to be equal to the receiver output voltage with no radio source in the antenna beam. VBAL may come from a voltage source with a potentiometer or a computer controlled Digital to Analog Converter (DAC). Careful setting of this voltage will allow making best use of the receiver sensitivity. Note that TN, the receiver internal noise, has been moved outside the basic receiver block because it is essential to understanding the adjustment of VBAL.
Once VBAL is set correctly the DC Amplifier gain can be set to a high value to allow seeing these very small changes. Any slight change in TN or receiver gain (G) will require readjustment of VBAL to keep the Analog to Digital Converter (ADC) or recording device within its scale. Another approach to acquiring VBAL is to measure the source of the noise we are subtracting out. This leads into the next receiver type.
Dicke Switch Receiver The Dicke switch receiver is a modification of a total power receiver. See Figure 6. It measures the difference between the input signal and a constant temperature reference load (TR). TR is ideally equal to the background antenna temperature. The two switches are flipped back and forth together. Typically the switching frequency is in the area of 500Hz. During the 1st half of the switch cycle R1 and C1 average the signal from the antenna. This average will reflect ( TA + TN )⋅G. During the 2nd half of the switch cycle R2 and C2 average the signal from the reference load. This average will reflect VBAL = ( TR + TN )⋅G. This is essentially the same value of VBAL that would have been set with the control in the Total Power Receiver with Offset. The important difference is that this automatically adjusts for changes in TN and G.
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When the two averages are subtracted the result is ( TA + TN )⋅G ‐ ( TR + TN )⋅G = ( TA ‐ TR )⋅ G Notice that TN does not show up in the result. The removal of TN⋅ G reduces the effects of gain variations. This technique reduces the effects of receiver input noise variation and gain variation. The Dicke receiver would be of little value if total power receivers could be built with perfect gain stability. In fact receiver gain stability is one of the worst problems of radio astronomy receiver design and the Dicke switch receiver is common. Note that we pay a sensitivity penalty because the receiver looks at the sky only half of the time. The improvement in stability is a good trade off in most cases. The receiver was drawn as shown to illustrate the evolution from a total power receiver with offset. In most Dicke switch receivers the output switch is arranged differently so that only one RC is used. Also part of the post detector amplification is done with an AC coupled amplifier between the total power receiver output and the switch. An AC coupled amplifier is OK here because we are interested in the changes in the total power receiver output at the switching rate. Dicke [3] used an interesting mechanical waveguide switch for the antenna switch in his original receiver. Reference [2] shows a modern design approach to the Dicke switch receiver. The 40 foot radio telescope at Greenbank, WV uses a Dicke switch receiver.
Noise Added Radiometer Ohm and Snell, [4], show a design for a noise added radiometer. This 1963 paper shows the advantage of injecting noise via a directional coupler over using the switch as done by Dicke. See Figure 7. A directional coupler can be made with a lower loss than a switch in the antenna circuit. Like the Dicke receiver, the noise added radiometer has two phases of operation. The two phases are typically switched back and forth at a 500Hz rate During the first phase the added noise is turned off, so the receiver is acting as a normal total power receiver. This is averaged R1 C1 as the “A” signal into the computing block.
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During the second phase the added noise is turned on. In a typical case the noise source is 10,000K and the directional coupler that adds this noise has a ‐30dB coupling factor. ‐30dB is a 1:1000 power ratio so TI looks like 10K added temperature from the antenna. Both directional couplers and noise source can be made to very high degrees of accuracy, so this added 10K can be very accurate. This receiver output is averaged in R2 C2 as the “B” signal into the computing block. The computation output is: Out =
(T A + TN ) ⋅ G A = (T A + TN + TI ) ⋅ G − (T A + TN ) ⋅ G B− A
Note that G cancels out, and after we combine terms we get: Out =
TA + TN TI
Note that receiver gain variations are totally removed from the result. TA+TN is given in units of TI. If we multiply Out by TI the result is TA+TN as an actual temperature. Ohm and Snell did all the computation on analog signal using vacuum tubes. A modern approach to this would use high resolution ADCs on the A and B signals, then do the temperature calculations with a digital computer. Reference [5] addresses this. In a 2008 paper [5] a noise added radiometer for detecting forest fires is shown. This radiometer used a 12GHz Satellite TV LNB with a precision noise source and a precision directional coupler. The remainder of this receiver was made from inexpensive components. The clock, or timing function, and everything after the total power receiver was implemented with an 8051 microcomputer chip. The 8051 sent the measured results to a computer via an RS232 serial link. If a receiver with accurate calibration is needed, this approach is viable. Reference [5] is available on the internet for free, and is worthwhile reading.
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Simple Interferometer A simple interferometer consists of two antennas with a signal combiner connected to a total power or Dicke switch receiver. The antennas are spaced some distance apart to create an interference pattern. The receiver itself performs the same as it does in single antenna applications.
Other Receivers The following receivers will be discussed in a future articles: Phase Switched Interferometer, Correlation Interferometer, Spectrometer, Pulsar Processing Receiver, and SETI Receiver
Appendix of terms B Bandwidth of receiver in Hz G Power Gain of an amplifier k Boltzmann’s constant = 1.38 × 10‐23 Joules / Kelvin K Kelvin unit of measure for temperature. It does not use the degree (°) symbol. P Power in watts τ Receiver averaging constant in Seconds T Temperature in K. Radio astronomy temperatures are always in K. TA Antenna temperature. This is the temperature of what the antenna sees. TI Injected noise level for a noise injection radiometer. TN Noise temperature of a receiver or amplifier. TR Reference Temperature for a Dicke switch receiver ΔT Minimum detectable temperature change of a receiver
[1] John D. Kraus, Radio Astronomy, 2nd Edition, Powell, OH, Cygnus‐Quasar Books, 1986. [2] Niels Skou and David LeVine, Microwave Radiometer Systems Design and Analysis, Norwood, MA, Artech House Inc., 2006. [3] R. H. Dicke, “The Measurement of Thermal Radiation at Microwave Frequencies”, The Review of Scientific Instruments, Volume 17, Number 7, July 1946. [Online] http://www.eng.yale.edu/rslab/internal/Papers/dickepaper.pdf [4] E. A. Ohm and W. W. Snell, “A Radiometer for a Space Communications Receiver,” Bell System Technical Journal, September 1963, pp 2047‐2080. [5] F. Alimenti, S. Bonafoni, S. Leone, G. Tasselli, P. Basili, L. Roselli, K. Solbach, “A Low‐Cost Microwave Radiometer for the Detection of Fire in Forest Environments” IEEE Transactions on Geoscience and Remote Sensing, Sept. 2008, pp. 2632 ‐ 2643. Paper can now be acquired for free. [Online] http://www.researchgate.net/publication/3205975_A_Low‐ Cost_Microwave_Radiometer_for_the_Detection_of_Fire_in_Forest_Environments
Biography of Bruce Randall Bruce Randall was born in 1949, so he is getting to be an old timer. Bruce got his first ham radio license in 1966. He has worked as an electronic engineer since 1978, with involvement in analog circuit design. His hobbies include astronomy, ham radio and radio astronomy. Bruce also enjoys canoeing and hiking, as time permits. He also fiddles with a 1972 MG sports car. His experiments with radio astronomy started in 1990, in the days of the chart recorder as the output device. He is interested in interferometers and possible extended baselines in the future.
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Noise|| Noise: Y‐factor versus Signal‐to‐Noise Ratio Christian Monstein and Whitham D. Reeve Often when people talk about noise, one is never sure what they are really talking about. Even scientists sometimes mix up the two noises, one based on the Y‐factor and the other based on a comparison to the background noise. In this paper we explain the difference and use the observation of solar radio bursts to illustrate some practical calculations.
Keywords: Callisto, Y‐factor, signal‐to‐noise ratio, SNR Introduction Gaussian noise, also called Additive White A radio telescope’s sensitivity is a measure of the weakest Gaussian Noise (AWGN), is noise that has celestial radio emission that can be detected with confidence. probability density function equal to a Sensitivity is directly related to the errors of measurement. The normal distribution, the familiar bell‐ emissions (“signals”) we measure usually appear as a small shaped probability plot shown below. The change in the receiver output as the radio source passes through area under the probability plot between two points is the probability that the the antenna beam or, as in the case of solar radio bursts, as an amplitude will fall within those two increase above the background noise level. The measurement points. errors and detection limits are determined by the fluctuations in the receiver output. Noise, which is inevitable, causes these fluctuations. There are many causes of noise and not all of them e d tu are completely random and follow a normal, or Gaussian, li p m a distribution (see sidebar Gaussian Noise); nevertheless, we can e is o assume they are Gaussian to simplify the mathematics needed N to analyze the radio telescope outputs. Time Noise || Noise Noise has zero average amplitude around its mean value, but the mean value itself does not have to be zero. For example, if the output of a 5 Vdc power supply is closely examined, there will be in addition to ac ripple some random noise due to the semiconductors (shot noise) and resistors (Johnson noise) in the power supply. The average, or mean, value of this noise will be 5 V. The noise amplitude about the mean is described by its standard deviation, usually indicated by the symbol σ (sigma). In spreadsheet programs it is indicated by the function STDDEV. The root mean square (rms) amplitude of noise equals 1 standard deviation, or 1σ. If we make a large number of instantaneous noise amplitude measurements, approximately 68.3% will fall within ±1σ of the mean and about 99.7% will fall within ±3σ. The equation for σ is described in any statistical mathematics handbook (for example, see [Davenport]). We can calculate the properties of emissions received by our radio telescopes in a couple ways. First, we can measure the ratio of the emission’s peak noise power to the mean value of the background noise power. This is called the Y‐factor. We also can measure the ratio of the received emissions noise power (“signal”) to the statistical variations in the background noise amplitude. This is called the signal‐to‐noise ratio, SNR, or, because all signal measurements include noise, it is more accurately signal + noise‐to‐noise ratio. Y‐factor is often confused with SNR, but the two measurements are not the same. Y‐Factor || Signal‐to‐Noise Ratio As mentioned above, the Y‐factor is the ratio of two noise power levels. In the two examples that follow, we measure one power at the peak of a received emission (hot measurement) and the other at the average + 4 s + 3 s + 2 s + 1 s 0 – 1 s – 2 s – 3 s – 4 s – 5 s
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value of the background noise (cold measurement). It should be noted that the hot measurement includes background noise. Y is calculated from
[1]
where I0 is the average noise power or intensity and I1 is the noise at the peak of the output. Usually the Y‐ factor is expressed in dB, or
[2]
Y‐factor is widely used in measuring the gain, noise temperature and noise factor of an amplifier. The Y‐ factor also is important in describing the radio telescope front end, which is the subsystem that converts the incoming radiation into an electrical signal compatible with the detector system. The components influencing the Y‐factor are the radio source’s flux, antenna effective area, noise figure of the low noise amplifer (LNA) at the antenna and the level of background noise power. The background noise itself is a combination of the galactic background, including cosmic microwave background (CMB) radiation, internal noise of the first amplifier and spillover from the ground and a few other minor contributions. Signal‐to‐noise ratio compares the peak intensity of the received emissions to the statistical characteristics of the background noise itself. Since the emissions received on Earth from most celestial radio sources are very weak, they are easily masked by the excursions of the background noise. If the rms of the noise is too high, a weak emission may be buried within it and undetectable. Therefore, the rms of the noise or some multiple of the rms indicates the detection probability. For example, an output due to the received emissions increasing > 2σ above the mean noise might be considered significant because the probability of such an output caused by ordinary noise is only 0.02. If we require higher confidence, the output must increase by a higher multiple. If the output increase is > 3σ, the probability that it is ordinary noise decreases to 0.001. Multiples of 2 to 5 are common. The signal‐to‐noise ratio is defined as
[3]
where σ denotes the rms of the background noise level. Usually the SNR is expressed in dB, or
[4]
Example 1 To illustratethe difference in signal‐noise and background‐noise, we use light‐curve data from a solar radio burst in the VHF range; see figure 1. The burst’s peak intensity occured near 129.4 MHz, so we can copy and paste the data at that frequency from the associated 2‐dimensional spectrum (intensity, frequency and time) into a spreadsheet or other program and plot it; see figure 2. We need to make several calculations at the frequency in question to determine the Y‐factor of the burst andbthe signal‐to‐noise ratio of the burst.
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We used an 8‐bit Callisto for our measurements. The measured intensities are proportional to the loading of Callisto’s analog‐digital converter (ADC), expressed in digits. For an 8‐bit ADC the loading can vary from 0 to 255. In our example radio burst, the peak intensity I1 = 185 digits and the background‐noise intensity I0 = 121 digits. In this case, the Y‐factor is 1.52 (Eq. [1]) or 1.84 dB (Eq. [2]). Both values used to calculate the Y‐ factor have a common reference (zero ADC loading). We can derive σ (rms noise or STDDEV) directly from the background noise by measuring its peak‐peak power amplitude. We mentioned earlier that multiples of σ in the range 2 to 5 are common. If we choose 3σ for reliable detection, then the peak‐peak noise is ± 3σ = 6σ. The minimum and maximum noise powers marked by blue dashed lines in figure 2 are designated s0 and s1. Their difference is set to 6σ, or [5] and In our example (figure 2), the noise is given by an upper value s1 = 128 digts and a lower value s0 = 123 digits. Therefore, the noise σ = (128 digits – 123 digits)/6 = 0.83digits. We can now calculate the SNR from Eq. [3], or snr = (185 digits – 121 digits) / 0.83 digits = 77.1 or 18.9 dB.
Figure 1~ Two‐dimensional spectrum plot of a typical solar radio type II burst observed at Siberian Solar Radio Telescope SSRT in Badary near Baikal Lake, Russia. We use the data from this spectrum to calculate the Y‐factor and SNR at the peak of the burst around 129.4 MHz.
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Figure 2 ~ Light‐curve extracted from figure 1 at 129.4 MHz showing peak signal amplitude above the background noise of the observed burst (difference between red dashed lines I1 and I0). I0 itself describes the background noise level. The blue dashed lines labeled s1 and s0 describes the 6 sigma (or 6 rms or 6 stdev) noise variance.
Conclusion We tried to explain the difference between Y‐factor and signal‐to‐noise ratio (SNR) which, in fact are totally different but colloquially treated as more or less the same. Be careful when discussing about noise, your discussion counterpart may talk about something else. Links: Callisto general information: http://www.e‐callisto.org/ References and further reading [Benz (2004)] Arnold O. Benz, Christian Monstein and Hansueli Meyer, CALLISTO, A New Concept for Solar Radio Spectrometers, Kluwer Academic Publishers, The Netherlands, 2004 [Davenport] William Davenport, Jr. and William Root, An Introduction to the Theory of Random Signals and Noise, IEEE Press, 1987
Above‐ The “Big Ear” Telescope located on the grounds of the Perkins Observatory at Ohio Wesleyan University from 1963 to 1998. http://www.bigear.org/
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Radio, Magnetic and (Possible) X‐Ray Observations of the X1 Solar Flare on 29 March 2014 Whitham D. Reeve
1. Introduction The observations reported here are of an impulsive class X1 flare that occurred at solar active region 2017 on 29 March 2014. This flare peaked at 1748 UTC (Coordinated Universal Time) and produced emissions over a wide frequency range for almost 30 minutes. The radio and magnetic observations are certainly associated with the flare, but the radiation observations could be a coincidence as discussed later. “A flare is defined as a sudden, rapid, and intense variation in brightness. A solar flare occurs when magnetic energy that has built up in the solar atmosphere is suddenly released. Radiation is emitted across virtually the entire electromagnetic spectrum, from radio waves at the long wavelength end, through optical emission to x‐rays and gamma rays at the short wavelength end. The amount of energy released is the equivalent of millions of 100‐megaton hydrogen bombs exploding Note: Links in braces { } and references in brackets [ ] are at the same time!” (from “What is a Solar Flare {NASA1}; see also the NASA Solar provided in section 6. Flare Theory educational web page {NASA2}).
2. Reported Details The X1 flare was summarized by Space Weather Prediction Center (SWPC) as a “complex Castelli‐U radio burst signature with a notable burst of 110,000 sfu on 245 MHz” {SWPC1}. SWPC provided additional details in the events list for 29 March {SWPC2} (table 1). Table 1 ~ Events reported by Space Weather Prediction Center for the X1 flare on 29 March 2014 8690 8690 8690 8690 8690 8690 8690 8690 8690 8690 8690 8690
#Event Begin Max End Obs Q Type Loc/Frq Particulars Reg# #------------------------------------------------------------------------------1735 1748 1754 G15 5 XRA 1-8A X1.0 4.2E-02 1738 1746 1816 HOL 3 FLA N11W32 2B ERU 1745 1747 1748 SAG G RBR 4995 650 CastelliU 1745 1746 1749 SAG G RBR 8800 1100 CastelliU 1745 1746 1748 SAG G RBR 15400 1000 CastelliU 1745 1746 1748 SAG G RBR 2695 360 CastelliU 1745 //// 1749 SAG C RSP 025-180 III/3 1745 1747 1749 SAG G RBR 410 1100 CastelliU 1745 1746 1748 SAG G RBR 1415 280 CastelliU 1745 1747 1751 SAG G RBR 245 110000 CastelliU 1745 1746 1748 SAG G RBR 610 420 CastelliU 1753 //// 1801 SAG C RSP 025-180 II/3 4508
2017 2017 2017 2017 2017 2017 2017 2017 2017 2017 2017 2017
Key to Events table: Begin, Max, End Times for event beginning, maximum and ending Obs Observatory: G15 = GOES 15; HOL = Holloman AFB, New Mexico USA; SAG = Sagamore Hill, Massachusetts USA Q Quality for optical: 1 (lowest) to 5 (highest); G = Good, C = Corrected report Type XRA = X‐ray event from GOES spacecraft; FLA = Optical flare in H‐ alpha; RBR = Fixed frequency radio burst; RSP = Sweep frequency radio burst Loc/Freq Location or Frequency:
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Particulars
Reg#
Additional information on the basis of report type: For radio bursts: Flux in sfu; For radio sweeps: Burst type and intensity; for XRA: X‐ray class; for FLA: Importance and brightness Solar region number assigned by SWPC
3. Observations Solar flares are unpredictable and the ones I have detected all Abbreviations produced surprising and interesting results. For this flare, I HF: High frequency (3 ~ 30 MHz) observed HF spot frequencies 20.0 and 25.2 MHz, HF spectrum from 18 to 30 MHz, geomagnetic effects at 0.1 Hz sampling rate UHF Ultra‐High Frequency (30 ~ 300 MHz and possible radiation effects at gamma or x‐ray energies above UTC Coordinated Universal Time 7 keV. I also refer to spectrum observations from 45 to 80 MHz VHF Very Higher Frequency (300 ~ 3000 MHz) and 220 to 450 MHz by fellow e‐Callisto observer and colleague Stan Nelson in Roswell, New Mexico (see {Meteor}). Instrumentation is briefly described in section 4. For additional information on e‐Callisto solar radio spectrometer network see {e‐Callisto} and for e‐Callisto data see {eC‐Data}. HF Spot Frequencies: Two spot frequencies, 20.0 and 25.2 MHz, were recorded (figure 1). Peak noise temperatures reached slightly above 82 million kelvins at 20 MHz and 30 million kelvins at 25.2 MHz.
Figure 1 ~ Calibrated Radio‐SkyPipe chart showing spot frequency noise temperature for a 5 min period centered on the solar flare time. Peak intensity received by this system was slightly more than 82 million kelvin at 20.0 MHz and 30 million kelvin at 25.2 MHz.
HF Spectrum: Continuous coverage from 18 to 30 MHz was recorded with 30 kHz resolution (figure 2). The spectrogram shows a series of radio bursts whose lower frequency slowly drifts upward over a 3 minute period.
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Figure 2 ~ Uncalibrated RadioSky‐Spectrograph spectrogram showing continuous frequency coverage from 18 to 30 MHz (30 kHz resolution). The color gain on the spectrogram was turned up to bring out the radio burst features but also brought out the radio frequency interference. The diagonal striping is thought to be from powerline noise and is evident throughout the spectrum, and additional RFI is shown by the thick horizontal line at 21.3 MHz.
VHF Spectrum: Continuous coverage from 45 to 80 MHz was recorded with 175 kHz resolution at Roswell, New Mexico USA (figure 3). The solar radio burst associated with the flare had a complex spectral shape with a deep dip in background noise at 1748. SWPC reported Type III (fast sweep) radio bursts from 1745 to 1749 and Type II (slow sweep) radio burst from 1753 to 1801 within the frequency range 25 and 180 MHz.
Figure 3 ~ Uncalibrated spectrogram showing continuous frequency coverage from 45 to 80 MHz. This spectrogram was prepared using Callisto data provided by Stan Nelson in Roswell, New Mexico. Note the deep dip in background noise between 45 and 55 MHz at 1748.
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VHF/UHF Spectrum: Continuous coverage from 220 to 450 MHz was recorded with 1.15 MHz resolution at Roswell, New Mexico USA (figure 4). The spectrum at these higher frequencies was not as complex as at lower frequencies. The radio flux density at 245 MHz was reported by SWPC as 110 000 sfu (solar flux unit, where 1 sfu = 10‐22 W/(m2‐Hz)).
Figure 4 ~ Uncalibrated spectrogram showing continuous frequency coverage from 220 to 450 MHz. The peak intensity (yellow area) occurred near 245 MHz at 1748, the same time reported by SWPC for peak x‐ray flux.
Geomagnetic Effects: Geomagnetic effects from a solar flare generally occur only if an Earth‐directed coronal mass ejection (CME) is associated with it, and those effects occur 2 to 9 days afterwards due to the relatively slow speed of the CME. However, occasionally, simultaneous effects are registered if the geomagnetic observatory is on the sunlit side of Earth at the time of a strong flare. I have observed these effects 1 or 2 times per year. In the case of the 29 March flare, a rare magnetic crochet registered on my magnetometer (figure 5). The name is given because the trace looks like a crochet hook, which is a tool used to draw thread or yarn through knotted loops. Radiation: Radiation observations are obtained in counts per minute – a relative indicator of the amount of radiation present. The coincidence monitor in this system logged 9 counts/min of simultaneous radiation detection by two sensors at about 2015 on 29 March, 2.5 h after Gamma and X‐Rays the solar flare, and also at about 1106 on 31 March, 42 hours after the flare (figure 6). The detector has been in operation since Gamma rays generally are energetic photons considered to have energies > 100 keV and, May 2011, and I have never before seen 9 counts per minute of according to the Planck relation, have frequencies 19 on the order of > 10 Hz (10 EHz) or wavelengths coincidence. Peak coincidence counts/min of 4, 5 and 6 are fairly ‐11 3 MeV; Beta > 50 keV; gamma/x‐ray > 7 keV. For additional detail, see {GM10}.
5. Conclusions The X1 solar flare of 29 March 2013 was observed over a very wide radio frequency range and caused a rarely observed simultaneous geomagnetic effect called a magnetic crochet. Also, a radiation detector at Anchorage, Alaska measured elevated coincidental counts from two independent radiation detectors 2.5 and 42 hours after the burst. Whether or not these counts were direct effects of the solar flare is inconclusive.
6. References and Links [RAE] Royal Academy of Engineering, Extreme Space Weather: Impacts on Engineered Systems and Infrastructure, February 2013, ISBN 1‐903496‐95‐0 {e‐Callisto} http://www.e‐callisto.org/
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{eC‐Data} {GM10} {Meteor} {NASA1} {NASA2} {SWPC1} {SWPC2}
http://soleil.i4ds.ch/solarradio/callistoQuicklooks/ http://www.blackcatsystems.com/GM/page5.html http://www.roswellmeteor.com/ http://hesperia.gsfc.nasa.gov/sftheory/flare.htm http://hesperia.gsfc.nasa.gov/sftheory/frame1.htm http://www.swpc.noaa.gov/ftpdir/forecasts/discussion/03291230forecast_discussion.txt http://www.swpc.noaa.gov/ftpdir/indices/events/20140329events.txt
7. Acknowledgements I am grateful to Stan Nelson of Roswell, New Mexico for the use of his Callisto data.
CARMA Telescope photo courtesy of Whit Reeve
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DETECTION OF JOVIAN VLF NOISE John Avellone/SARA
[email protected] Introduction: This article was developed in response to the presentation by David E. Fields at the 2011 SARA Conference: “Detection of Jupiter Radio Emissions well below the Plasma Cutoff Frequency ‐ Implementations for SID Monitoring”. The following questions are addressed: I. Does Jupiter produce VLF (very low frequency) noise? II. Can Jovian VLF noise propagate through the Earth’s ionosphere? III. Did Nikola Tesla detect Jovian VLF noise? IV. Can an amateur experiment detect Jovian VLF noise? I. Jupiter produces VLF noise A. The two Voyager spacecraft made possible investigation of some of Jupiter’s radio emissions at close range and down to very low radio frequencies (VLF). Data collected led to discovery of two distinct components of radiation at kilometer wavelengths. B. The two components are broadband and narrowband kilometric burst radiation. The spectral profiles of these components are shown in Figure 1. (Taken from reference [1]) Both components are characterized by typically two hour duration.
C. The source of the broadband component (10 to 1000 kHz) is centered on the central meridian longitude (CML) of Jupiter’s north magnetic pole (CML = 200 degrees). Note: This is the “A” region on Jupiter’s high frequency (HF) radio emission map. D. The narrowband component (100 kHz, +/‐ 20 kHz) seems to originate from a region 8 to 9 Jovian radii from the cloud top level. E. Thus, Jupiter’s “A” region (CML=200 degrees) is a source of strong VLF broadband burst emission.
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Figure 1. The two components of radiation at kilometer wavelengths are broadband and narrowband kilometric burst radiation. The spectral profiles of these components are shown above.
II. Jovian VLF can propagate through the Earth’s ionosphere A. The following discussion summarizes the relevant points from ref [2]. B. Basically the right ‐ hand ‐ circularly polarized (RCP) extraordinary VLF wave, as defined by the Appleton ‐ Hartree equation, Figure 2 (Taken from reference [2]), can propagate along a geomagnetic field line through the night time ionosphere down to the surface with little attenuation. This was experimentally validated by the U. S. Navy LORIS tests (in 1961) demonstrating detection of an 18 kHz signal transmitted from the ground to a satellite.
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Figure 2‐ the Appleton ‐ Hartree equation
C. For possible night time detection of RCP Jovian VLF bursts, the magnetic field’s inclination at the location of the ground observer would have to match the planet’s altitude at a time when the Jovian CML was about 200 degrees. The possible window of frequencies present and able to pass through the ionosphere with minimal attenuation looks to be from 10 kHz up to perhaps 200 kHz. The lower limit (10 kHz) represents the lower cutoff of the Jovian kilometric radiation. The upper limit (200 kHz) is controlled by the index of refraction of the Earth’s
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ionosphere to the RCP extraordinary wave. Figure 3 (Also taken from reference [2]) shows this upper frequency cutoff.
Figure 3
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III. Did Nikola Tesla detect Jovian VLF noise?
A. Probably not. B. In reference [3], Corum and Corum propose that Nikola Tesla may have aurally detected Jovian noise bursts, on one evening in late July 1899, while testing the sensitivity of his radio receiver during his Colorado Springs experiments. The particular event they identify was a Jovian Non ‐ Io ‐ A storm predicted to have occurred on 07/21/1899 between 7:41 and 9:12 PM local time (07/22/1899/02:41 ‐ 04:41 UT). From his Colorado Springs Notes [4], Tesla was indeed working on receiver circuits on 21 July, but (some ambiguity here) was actually operating the receiver, and listening aurally to distant thunderstorms, late on the evening of 28 July. Again from the “Notes” (and again with some ambiguity) it seems to be during this listening period that Tesla later concluded (letter to the Red Cross, etc) that he had possibly heard extra ‐ terrestrial signals. To quote from the “Notes”: “We have a message from another world, unknown and remote. It reads: one...two...three”. From one Tesla biographer [5]: “Another of Tesla’s claimed discoveries at Colorado Springs came late one night as he was working his powerful and sensitive radio receiver. Only the elderly Mr. Dozer, the carpenter, remained on duty. Suddenly the inventor became aware of strange rhythmic sounds on the receiver. He could think of no possible explanation for such a regular pattern unless it was an effort being made to communicate with Earth by living creatures on another planet.” This rather dramatic conclusion may be explained by comments from another biographer [6]: “Tesla, as one of numerous adherents to the group ‐ fantasy belief that Mars was inhabited, assumed that the impulses stemmed from there”. C. If it is assumed that Tesla actually heard something, as opposed to imagining a signal amid the noise background, what are the possible sources? It is unlikely to have been Jupiter. There was another Jovian “A” event on 28 July, around 8:30 PM local time. However, Tesla detected the “numbers signal” late, around midnight. This would have been two to three hours after the “A” event and around the time of Jupiter’s setting. As an alternative, there may have been a real signal to detect. To again quote a biographer [6]: “On July 28, the very date it has been hypothesized that Tesla received the signals, Marconi was with the British Admiralty...demonstrating his wireless apparatus between ships in mock battle maneuvers over distances of thirty miles, fifty‐five miles and eighty‐six miles (95 miles from [7])”. Ref [7} further specifies that the ships were the two fast scout cruisers HMS EUROPA and HMS JUNO and the capital ship HMS ALEXANDRA. The ships were fitted with aerials 150' high. Elsewhere in ref [7] is this description of operation of a Marconi shore transmitting station: “...sparks a foot long and thick as a man’s wrist were being generated in sequence of three short bursts (5 seconds long for a “dot”). The ground shook each time the transmitter fired the dots of the letter “S” (dot...dot...dot) in Morse code”. To go back to ref [6]: ...”If Tesla was monitoring his equipment at twelve midnight, it would have been about 8 AM in England, so the times correlate as well...he (Tesla) unfortunately provided, through Marconi’s piracy, the very oscillators used to transmit the signals. The transmitter on the high seas, therefore, was attuned to the receiving equipment in Colorado”. As a side note, Corum and Corum [3] estimate that the design of Tesla’s coils would have worked down to 10 kHz. In his “Notes”, Tesla calculated that his transmitter coils could achieve frequencies around 40 kHz. D. Thus, if Tesla did hear a real signal around midnight on 28 July 1899, it was likely the Morse code letter “S” transmitted by his rival, Marconi, an ocean and half a continent away. This, by itself, was a tremendous
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accomplishment. IV. An experiment to detect Jovian VLF
A. EQUIPMENT 1. A simple loop antenna. This consisted of 4‐ conductor flat telephone cord wrapped three times around the circumference of a 36" diameter child’s plastic play hoop, offset and cross connected. This loop does well in monitoring the 24 kHz NAA VLF signal for sudden Ionospheric disturbance (SID) events. To roughly orient the plane of the loop to approximate Jupiter’s position when near the local meridian, it was suspended in a vertical east ‐ west plane. A loop is capable of receiving both circularly and linearly polarized radiation, but cannot distinguish between the two. 2. A VLF to HF up‐converter. This was built [8] from an article in the November 2009 issue of QSL magazine. The converter takes all frequencies picked up by the loop, filters out all those above 500 kHz, adds 4.0 MHz and amplifies the resulting sum frequencies. 3. One or two general coverage FM/AM/SW/LW receivers (SANGEAN 808 and 803). The output from the up‐ converter was fed to the “external antenna” jack on the receivers. The receivers were tuned to a SW frequency equal to the VLF frequency selected plus 4 MHz. 4. The audio output from the receivers was taken to the “line” jack of a soundcard in a desktop PC running “Sky Pipe” at 10 samples per second. B. RECORDING PROCEDURE 1. Hours ‐ long VLF recordings were made at frequencies from 5 to 40 kHz that included periods when Jovian “Io‐ A” and “Non‐Io‐A” events were predicted by Radio Jupiter PRO 3. 2. Each collection run was later edited in time span and adjusted in amplitude to make visual evaluation of the resulting printed charts easier. In general, these charts showed a great deal of interference, both from local electrical equipment (QRM) and distant natural sources such as lightning accompanying weather fronts (QRN). 3. The basic question that needed to be addressed was what/how to identify, evaluate, or quantify any VLF activity spikes present on the charts. From previous work, it seemed pointless to attempt an exact burst by burst correlation of time of a VLF spike with the time of a HF spike. Instead, the more basic approach of looking for periods of “clumping” of the VLF spikes was adopted. This method has good precedent. It was basically that used by Burke and Franklin in their 1955 investigation first identifying HF noise bursts with Jupiter [9]. Many of the charts exhibited some degree of “clumping”. Figure 4 shows a good example.
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Figure 4‐ Example of “clumping” of the VLF spikes
4. In analysis of the collected data, the degree of, and times of, VLF event clumping, versus the time of CML = 200 degrees, the altitude of Jupiter at CML = 200 degrees, and the presence or absence of Io were examined. C. THE COLLECTED DATA SET 1. About 27 VLF data runs, totaling about 182 hours of collection were recorded between 06 December 2013
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and 28 February 2014. Table 1 summarizes the basic parameters of these observations. In the table, the respective columns describe: o Date of the collection (MM/DD/YY) o Start/Stop times (hh/mm‐hh/mm, in UT) o Time of CML = 200 degrees o Altitude of Jupiter at CML = 200 degrees o Was it a Io‐A (“IA”) or a Non Io‐A (NIA) event o The VLF frequency/frequencies used (in kHz) o Did “clumping” occur during the recording (“Y”/”N”) o Was “clumping’ observed at CML = 200 degrees (“Y”/”N”) TABLE 1 ~ VLF OBSERVATIONS DATE 12/06/13 12/11/13 12/29/13 12/30/13 12/30‐31/13 01/01/14 01/03‐04/14 01/06/14 01/07‐08/14 01/09‐10/14 01/14/14 01/17/14 01/23/14 01/24/14 01/25‐26/14 01/30/14 01/31/14 02/06/14 02/07/14 02/08/14 02/09/14 02/10/14 02/17‐18/14 02/20/14 02/23/14 02/25/14 02/28/14
START/STOP 0440‐0450 0107‐0147 0500‐1200 0600‐1400 2300‐0100
CML200 0440 0200 0610 1230 2345
ALT IA/NIA? 40 IA 16 IA 75 IA 00 NIA 18 IA
FREQ CLUMPING? 19 Y 19 N 10 Y 10 Y 10 Y?
AT CML200? Y N Y N Y?
0315‐0515 2300‐1300 1000‐1200 2300‐0400 2300‐0400 0800‐1200 0000‐1200 0000‐0800 0000‐1200 2200‐0100 0000‐1000 0300‐1100
0345 0600 1145 0015 0015 0900 0645 0130 0700 2345 0220 0830
60 NIA 75 NIA 12 IA 30 IA 30 IA 30 IA 60 NIA 48 IA 38 NIA 40 NIA 70 IA 20 NIA
05 & 10 10 12 & 19 19 12 & 18 19 17 19 18 19 18 20
Y(@10) Y N Y Y? N Y Y N N Y Y?
Y Y? N N N N Y Y N N Y N
0315‐0915 0500‐1100 2000‐2400 2000‐2400 0600‐0900 2030‐0430 0100‐1300 0230‐1230 0000‐1000 0030‐0830
0300 0820 2040 2030 0600 2040 0430 0220 0315 0100
70 IA 20 NIA 08 IA 15 IA 37 NIA 20 NIA 60 IA 70 IA 62 NIA 73 NIA
19 19 19 19 18 19 30 & 40 18 & 19 18 18
Y Y? Y Y N Y? Y Y Y Y
Y Y? Y? Y? N N Y N Y Y
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D. VLF DATA ANALYSIS 1. The observations summarized in Table 1 were grouped into three subsets depending on the degree of VLF clumping around the time of CML = 200 degrees and compared with the altitude of Jupiter and the Io/Non Io condition. GROUP 1: Good Clumping at CML 200 Date Altitude IA/NIA? 12/06/13 40 IA 12/29/13 75 IA 01/30/14 70 IA 02/06/14 70 IA 02/20/14 60 IA 02/25/14 62 NIA GROUP 2: Weak Clumping at CML 200 Date Altitude IA/NIA? 01/01/14 60 NIA 01/03‐04/14 75 NIA 01/17/14 60 NIA 01/23/14 48 IA 02/07/14 20 NIA 02/08/14 08 IA 02/09/14 15 IA 02/28/14 17 NIA GROUP 3: No Clumping at CML 200 Date Altitude IA/NIA? 12/11/13 16 IA 12/30/13 00 NIA 01/06/14 12 NIA 01/07‐08/14 30 IA 01/09‐10/14 30 IA 01/14/14 30 IA 01/24/14 38 NIA 01/25‐26/14 40 NIA 01/31/14 20 NIA 02/10/14 37 NIA 02/23/14 70 IA
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V. CONCLUSIONS The way the observations in these three groups seem to show dependence on the parameters of : a) Altitude of Jupiter when the CML = 200 degrees, and b) Whether or not the Galilean satellite, Io, is involved suggest the following conclusions: 1. VLF activity associated with Jupiter may have been observed at frequencies between 10 and 40 kHz. 2. The degree of activity is enhanced when the altitude of Jupiter at CML = 200 degrees is commensurate with the magnetic field line inclination (about 67 degrees) at the observer’s location. 3. Stronger levels of VLF activity seem coincident with presence of the moon Io. 4. Further observations are needed for validation. VI. REFERENCES [1] RADIO ASTRONOMY, 2nd edition, John D. Krauss, Cygnus ‐ Quasar Books, c. 1986 [2] “Detection of Jupiter Radio Emissions well below the Plasma Cutoff Frequency ‐ Implementations for SID Monitoring”, David E. Fields, 2011 SARA Conference Proceedings [3] Kenneth L. Corum and James F. Corum, “Nikola Tesla And The Planetary Radio Signals”, 5 th International Tesla Conference, Tesla III Millennium, c.1996 [4] NIKOLA TESLA COLARADO SPRINGS NOTES 1899 ‐ 1900, compiled and edited by A. Marincic, Nolit, Beograd, Yugoslavia, 1978 [5] Tesla, Man Out of Time, Margaret Cheney, Prentice Hall, c.1981 [6] WIZARD, The Life and Times of Nikola Tesla, Marc J. Seifer, Birch Lane Press/Carol Publishing, c.1996 [7] SIGNOR MARCONI’S MAGIC BOX, Gavin Weightman, DA CAPO PRESS, c.2003 [8] Thanks to the assistance of Bill Phillips of the Charlottesville Astronomical Society [9] Burke, B.F., and K.L. Franklin: “Observations of a Variable Radio Source Associated with the Planet Jupiter” J. Geophys. Res., Vol 60, pp 213‐217, 1955. VII. BIOGRAPHY John Avellone, a member of the “silent generation”, grew up on the south shore of Lake Erie where the sky, when occasionally clear, often showed the aurora borealis. He earned a BS in Astronomy from Case Institute of Technology and a MS in Astronomy from the Ohio State University. He was a career civil servant in the Department of Defense for three decades. He has been enjoying the post retirement years pursuing various astronomical activities, most recently from the quiet of the Shenandoah Valley.
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FM notch filter in front ‐ and ‐ behind the low noise amplifier of a Callisto Radio Spectrometer in Gauribidanur, India Christian Monstein Abstract In the framework of IHY2007 a Callisto spectrometer [Benz(2004)] was installed and set into operation at the location of the solar heliograph in Gauribidanur, India. At that time the level of radio frequency interference (RFI) was amazingly low. In recent years more and more FM broadcast transmitters were installed with high power compared to the requirements of radio astronomical observations. So, the spectral observations with Callisto experienced more and more interference by these FM transmitters. Recently an FM‐notch filter was installed between the low noise amplifier and Callisto, but it did not work out. The notch filter was then moved to the input of the LNA and the result was much better, as expected from theoretical concepts.
Keywords: Callisto, RFI, notch filter Interference due to nearby FM transmitters The nearby FM transmitters produce a lot of interference into the signal chain of the low noise amplifier (LNA) and Callisto spectrometer. A notch filter between the LNA and Callisto suppresses the interference seen by Callisto but, overall, it is ineffective because the LNA has been saturated by the FM signals. The interference introduces vertical structures in the spectrum (figures 1 and 2). For the measurements described here, a Band Stop Filter ZX75BS‐88108‐S+ from Mini‐Circuits (~US70$) was used.
Figure 1~ Callisto spectrum from a FITS‐file observed with a notch filter between the LNA and Callisto. The signal between 80 and 115 MHz is attenuated (dark horizontal area) but the LNA itself is suffering from strong FM transmitters, which produce cross‐modulation due to saturation in the semiconductors (non‐ linear range). This plot shows raw data with no manipulation. Saturation and cross‐ modulation introduced by strong FM signals produces vertical stripes in the spectrum over all frequencies.
Figure 2~ This plot shows the same data as in figure 1 but with the background subtracted. Now we can much better see the vertical structures introduced by interference from nearby FM transmitters. Data quality is quite bad making it difficult to find and analyze solar radio bursts.
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The entire signal chain should be protected from strong man‐made signals. This can be easily accomplished by inserting an FM notch filter to suppress all signals between about 80 and 115 MHz. The only way to improve the present situation is to switch the notch filter to the front of the signal chain at the input to the LNA. This action was carried out on March 15th 2014. This dramatically improved the situation; cross‐ modulations can hardly be found in the dynamic spectra (figures 3 and 4). Figure 3~ Raw spectrum plot with a notch filter inserted in front of the LNA. The notched band can clearly be identified around the FM range (black horizontal area). Only minor cross‐modulation takes place, probably introduced due to air‐ communication around 128 MHz. Near 03:26:01 UT and below 85 MHz we can identify a small type III solar radio burst. In this plot background is not subtracted, it shows original data as observed by Callisto spectrometer.
Figure 4~ The same spectrum as shown in figure 3 but with background subtracted. There is only minor interference detectable around 165 MHz, most probably radio‐ communication by security or fire brigade. The solar type III burst can clearly be identified and scientifically analyzed.
Conclusion It has been demonstrated, that a notch‐filter can help to get rid of interference but only by accepting data loss in the notched band, of course. It’s very important to switch in the filter as close to the interferer as possible, in our case between the antenna and low noise amplifier. There is no sense in putting the filter between the LNA and spectrometer because the LNA is already saturated and introducing its own interference into the spectrometer. With the filter properly installed, the general data quality is much better than before and we hope that in the future no new strong transmitters will be set into operation. In principle we can install several notch filters in series to get rid of more than one interfering frequency or band. However, the insertion loss also increases, which reduces the instrument sensitivity. Therefore, it is better to
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avoid any nearby transmission or to put the instruments at a remote area without any interfering transmitters. Links: Callisto general information: http://www.e‐callisto.org/ Access to the data archive: http://soleil.i4ds.ch/solarradio/callistoQuicklooks/ References and further reading [Benz (2004)] Arnold O. Benz, Christian Monstein and Hansueli Meyer, CALLISTO, A New Concept for Solar Radio Spectrometers, Kluwer Academic Publishers, The Netherlands, 2004. Meet the author: Christian Monstein is a native of Switzerland and lives in Freienbach. He obtained Electronics Engineer, B.S. degree at Konstanz University, Germany. Christian is a SARA member since 1987 and is licensed as amateur radio operator, HB9SCT. He has experience designing test systems in the telecommunications industry and is proficient in several programming languages including C and C++. He presently works at ETH‐Zürich on the design of digital radio spectrometers (frequency agile and FFT) and is responsible for the hardware and software associated with the e‐CALLISTO Project. He also has participated in the European Space Agency space telescope Herschel (HIFI), European Southern Observatory project MUSE for VLT in Chile, and NANTEN2 (delivery of the radio spectrometer for the Submillimeter Observatory at Pampa la Bola, Chile). Currently he is quite involved to prepare the radio telescopes for cosmological test observations. He plays also the role of a coordinator of SetiLeague in Switzerland. Email:
[email protected]
Quotable Quote Bad times have a scientific value. These are occasions a good learner would not miss.
Ralph Waldo Emerson
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An Antenna with an Historical Past Jeffrey M. Lichtman SARA Founder, Director Emeritus Radio Astronomy Supplies
About 8 years ago, I became acquainted with a very gifted person, Dr. Rene Lee of New Mexico. Over the years, Dr. Lee has been involved in many areas of science and technology.
Some years back, Dr. Lee acquired a *D. S. Kennedy, 32 foot dish antenna from a fellow New Mexico resident who rescued it from White Sands Proving Ground in New Mexico. The antenna was a player in the US space program and was used for receiving Telemetry (http://en.wikipedia.org/wiki/Telemetry) from spacecraft missions. *(D.S. Kennedy was one of the supreme antenna manufacturers in the 1960s and 70s.)
(The original ad here shows a much larger version of the one described in this piece) Dr. Lee has stored this antenna, under enclosure to protect the antenna. The antenna, is still in excellent condition right down to the reflector surface and gray finish. Original plans were to build a mount and use it for radio astronomy.
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D. S. Kennedy Pedals
D. S. Kennedy Antenna in Australia In November 2012, a good friend of mine, Franco Cappiello of Milan, Italy (
[email protected]) visited us for a week. While staying with us, we took a road trip to the VLA in New Mexico. Franco is a radio astronomy enthusiast and also an owner of a Radio Astronomy Supplies, Spectracyber Radio Telescope.
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Franco and 3 mtr. antenna on his roof deck in Milan
While on our trip, in conversation, I told him of my friend Dr. Lee and the 32 foot antenna. His eyes lit up! Franco immediately thought how great that would be to possibly acquire this antenna and have it shipped to Italy for doing real science. He then told me of a group of friends that he meets with and their interest in Radio Astronomy. Franco also mentioned that he instructs at a local university plus being the owner of an engineering company involved in the energy area. In addition, his resources include a full machine shop with all the tools and expertise required to construct a mount for the antenna. So, it has come to pass that the dream will be coming true. This wonderful piece of American ingenuity with a great past will find itself around the world and perhaps once again play a role in research radio astronomy. For those of you who want to follow the continuing story, you can contact Franco at: (
[email protected] or Jeff Lichtman at:
[email protected] References http://www.bing.com/images/search?q=D.+S.+Kennedy+Antenna&qpvt=D.+S.+Kennedy+Antenna& FORM=IGRE http://www.wickedlocal.com/cohasset/news/x563276961#axzz2SAWhZ0NY (http://www.wickedlocal.com/cohasset/news/x1001333925/The‐business‐of‐ antennas#axzz2SAWhZ0NY
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Report from an expert meeting at United Nations Office for Outer Space Affairs (UNOOSA) Christian Monstein Abstract Between February 10 and 11, 2014 there was an expert meeting organized by the UN and NASA with the title “Improving Space Weather Forecasting in the Next Decade” (figure 1). The meeting was held at the United Nations Office in Vienna, Austria on the margins of the 51st Session of the Scientific and Technical Subcommittee of the Committee on the Peaceful Uses of Outer Space (COPUOS), also in Vienna. The meeting place was Conference Room C6, Building “C”, 7th floor, Vienna International Centre (figure 2). In total 46 participants from 18 countries attended the meeting. Many very interesting talks were given about different instrument arrays, distributed worldwide [Talks2014]. I made a presentation on the e‐Callisto solar radio spectrometer network, which is one of the instruments in the International Space Weather Initiative (ISWI) [Monstein]. Beginning with the International Heliophysical Year 2007 (IHY2007) until the recent International Space Weather Initiative, instruments costing more than US10 M$ have been delivered to developing countries, installed and set into operation. Everybody within the experts group agreed that the activities should continue and many different reasons were given. Therefore recommendations were filed to the attention of the plenary meeting of COPUOS. The final text of the recommendation is given below with permission of Joseph M Davila, NASA‐Goddard Space Flight Center, USA. Figure 1 ~ Meeting announcement. (Image courtesy of George Maeda)
Expert Meeting on Improving Space Weather Forecasting in the Next Decade 10 ‐ 11 February 2014 Vienna, Austria Meeting Summary
Background Space weather originates at the Sun due to its magnetic Spacecraft: variability. Solar variability (plasma, particles, and Hinode ~ “Sunrise”, formerly Solar‐B electromagnetic emissions) occurs at all timescales – seconds, hours, decades, to millennium– the most common one being the SDO ~ Solar Dynamics Observatory 11‐year sunspot cycle. The short and long‐term variability in the SOHO~ Solar and Heliospheric Observatory form of solar storms have significant effects on Earth’s upper atmosphere and the near‐Earth space radiation environment. For STEREO ~ Solar TErrestrialRElations Observatory example, the variability of the ionosphere affects the propagation of radio waves, causing GNSS position errors and interruptions in HF communications. The United Nations has supported the International Heliophysical Year and the International Space Weather Initiative (ISWI) to deploy new arrays of instruments to study the entire heliophysical system from the Sun to the ionosphere. This was accomplished through a cooperative program between instrument providers and
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instrument host institutions. In the future these arrays will provide data for space weather forecasting and nowcasting. Space weather forecasts have been available for some time. However, during the past decade new sources of data have become available both from space and ground‐based instruments. New data from space‐based instruments onboard SOHO, Hinode, STEREO, and SDO have greatly improved the understanding of space weather, in terms of forecasting and basic physical understanding. In addition, STEREO observations of the vast region between the Sun and Earth have demonstrated the importance of viewing Earth‐affecting CMEs away the Sun‐Earth line. New theoretical models have provided improved forecasts as well as insight into the physics of solar and ionospheric phenomena including influences from the troposphere. There has been significant effort in the last few years to reduce the cost of space missions. As part of this trend, the delegates noted the rapid development of cubesat technology, and the growing capabilities of these small satellites for providing space weather data. In parallel there is an increasing ability for the miniaturization of the instrumentation needed. These developments could provide the path for less‐ expensive observations relevant to space weather. Space weather is inherently an international endeavor. Space weather events which affect Earth are large‐ scale and typically affect multiple nations simultaneously. In addition, space weather events drive the entire radiation environment in a large region surrounding Earth where the orbiting satellites of all nations are positioned. Because of this the mitigation activities in response to space weather forecasts are of great international interest. The purpose of this meeting was to look at the future of space weather forecasting and to formulate recommendations that will lead to improved forecasts in the next decade. It is anticipated that all or some of these recommendations will be implemented as part of the regular agenda item on Space Weather of the Scientific and Technical Subcommittee on the Peaceful Uses of Outer Space (COPUOS). Recommendations The delegates to the Expert Meeting on Improving Space Weather Forecasting in the Next Decade unanimously • Encourages the continued support for research in Heliophysics both as a scientific endeavor that enables a detailed understanding of the phenomena, and as a tool that can be exploited for space weather applications; The relevant agencies are encouraged to work together to ensure that both of these efforts are adequately supported, for the benefit of science and society; • Recognizes the success of observations in recent projects, and critical information gained from them, and recommends an urgent strategy to ensure that there is continued access to observations of transients in the inner heliosphere, in particular, the Earth‐directed events; • Recommends continuation of the deployment of new instruments and instrument arrays through the ISWI, along with education and public outreach; • Recommends that information relevant for space weather from all sources be freely and openly shared, including data, calibration, analysis tools, and best‐practices for operation;
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• Recommends that data products be standardized to allow the data to be easily ingested into research and forecast models, and systems for automated data processing be developed to autonomously identify significant events; • Supports the development, validation and transition of research‐based models for forecasting and nowcasting; • Recommends that data products and analysis tools from space‐based and ground‐based instrument arrays be coordinated to maximize their utility for space weather research and for operational forecasting; • Recommends that the space weather science/requirements for the forecasting of space weather at other planets be developed with special emphasis toward supporting the robotic exploration of these planets; • Recommends that studies of comparative astrophysics of Sun‐like stars be used to provide more realistic limits on the magnitude of extreme solar events; • Encourages a central facility for sharing and hosting of data from space‐ and ground‐based instruments relevant for space weather research and forecasting facilitated via existing virtual observatories; • Encourages establishing an international organization for the sharing and hosting of standardized models related to space weather forecasting and that the models be made available to the general scientific community.
Figure 2 ~ Building complex of United Nations in Vienna, Austria. (Image © Christian Monstein, Feb. 2014)
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References and further reading [Talks2014] http://www.serc.kyushu‐u.ac.jp/iswi/extmtg_2014feb/ [Monstein] The talk by the author at the conference about the e‐Callisto network can be found here: http://www.serc.kyushu‐ u.ac.jp/iswi/extmtg_2014feb/Session%204%20Feb11%20AM1/4_4_Monstein/4_4_Monstein.ppt Meet the author: Christian Monstein is a native of Switzerland and lives in Freienbach. He obtained Electronics Engineer, B.S. degree at Konstanz University, Germany. Christian is a SARA member since 1987 and is licensed as amateur radio operator, HB9SCT. He has experience designing test systems in the telecommunications industry and is proficient in several programming languages including C and C++. He presently works at ETH‐Zürich on the design of digital radio spectrometers (frequency agile and FFT) and is responsible for the hardware and software associated with the e‐CALLISTO Project. He also has participated in the European Space Agency space telescope Herschel (HIFI), European Southern Observatory project MUSE for VLT in Chile, and NANTEN2 (delivery of the radio spectrometer for the Submillimeter Observatory at Pampa la Bola, Chile). Christian represents Switzerland within the Committee on Radio Astronomy Frequencies (CRAF). Currently he is quite involved to prepare the radio telescopes for cosmological test observations. He plays also the role of a coordinator of SetiLeague in Switzerland. Email:
[email protected]
Quotable Quote “Equipped with his five senses, man explores the universe around him and calls the adventure Science.” Edwin Powell Hubble
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Transmission Line Details ~ Software Calculator Review Whitham D. Reeve 1. Transmission Line Model
Coaxial cable is a type of transmission line of great importance to anyone working with radio frequencies. We often are concerned with the attenuation introduced by a transmission line. Attenuation is the reduction in power from the input to the output; some of the input power may be dissipated as heat in the line due to resistance and dielectric losses or reflected back to the source, so the output power always is smaller than the input. We are interested in the relationship between a transmission line’s physical and electrical length so we can build phasing cables and bandstop filters (traps). We also can use transmission lines to tune a circuit or antenna and to make couplers and impedance transformers. Transmission lines can be electrically modeled a number of ways. A typical model uses distributed transmission line parameters consisting of resistance R, conductance G, inductance L and capacitance C, all expressed per unit length of line. For example, the resistance can be expressed in ohms/m, ohms/100 m or ohms/1000 m. The schematic of a distributed transmission line model shows conventional symbols (figure 1). However, the resistance and other parameters Note: Links in braces { } and references in brackets [ ] are are evenly distributed along some arbitrary length of line (for the math provided in the section 3. associated with development of a distributed transmission line model, see [Reeve‐92]). R/4
L/4
L/4
C R/4
R/4
G
L/4
L/4
R/4
Figure 1 ~ Balanced‐T transmission line model based on series resistance R, series inductance L, shunt conductance G and shunt capacitance C per unit length of line. The length associated with the model elements is arbitrarily small. Dielectric losses are represented by the shunt conductance, and attenuation is represented by series resistance and inductance and shunt capacitance. The parameters typically vary with frequency and temperature. (Image © 2003 W. Reeve)
The R, G, L and C parameters often are called primary constants, but this is a misappropriation of terms because they are not at all constant. There usually are significant variations with temperature (and other environmental factors) and frequency and due to normal manufacturing tolerances. These primary parameters are not of much direct use to a practitioner. In practical applications we use secondary parameters such as attenuation (or loss), phase delay and velocity of propagation. Primary parameters usually are derived from measurements of the secondary parameters. I will use the terms attenuation and loss interchangeably although loss generally requires qualification as to type (transducer loss, insertion loss, and so on) and their differences are ignored for purposes of this article.
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2. Transmission Line Details Although transmission lines encompass waveguides, open wires, twisted pair cables and coaxial cables, I am concerned only with coaxial cables in this review. Coaxial cable manufacturers have datasheets, software tools, online calculators, charts and tables that provide secondary parameters. The calculators are easy to use but they usually provide only basic results such as attenuation for a given line length and frequency. We often need to know more about a coaxial cable application than can be derived from manufacturer’s datasheets or charts. Perhaps we would like to change the line resistance (due, for example, to a temperature change) or load impedance to see what the effects are. Over the years, nomographs and then software applications have been developed for this purpose. One such software application is Transmission Line Details (figure 2), which is described in this review and available for free at {TLD}.
Figure 2 ~ Transmission Line Details user interface with inputs in the upper panel and calculation results in the lower panel. The Smith Chart in the center of the lower panel is a nice visual aid. The program has stored parameters for many cable types and uses the coefficients K0, K1 and K2 in its calculations. The traditional transmission line model parameters R, L, G and C that correspond to these coefficients are shown on the right side of the upper panel. The user can change the coefficients associated with a particular cable by using the scroll buttons next to each one. These changes disappear when a new cable is chosen or when the program is closed. They also can be reset to default values by pressing a reset button that appears when a parameter is changed.
As of this writing (March 2014) the latest version of this program is v2.0, which was last updated in March 2011. The program is not installed in the conventional Windows sense; the TLDetails.exe executable is simply run from the Desktop or any other convenient location. There is no hassle when it comes time to uninstall the program – you simply delete the file.
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It is often the case that a software application takes longer to learn than simply doing the calculations by hand. Fortunately, Transmission Line Details is simple to use but many of the calculations can be quickly done by hand. Applications like this really are useful when there is a need for repetitive calculations and investigation of different scenarios. This program has no help file or manual but it does have brief “tips” that pop up when you hoover the mouse cursor over the text boxes. I do not believe it needs a help file or manual, but users who are unfamiliar with transmission lines can easily get themselves into trouble (this is true of any software application that allows the user to change parameters). Transmission Line Details, or TLD for short, includes data for about 100 different coaxial cables and also accepts user input for custom cables; however, there is no information on how the user is supposed prepare or obtain the necessary data for the custom cables. All calculations appear to be based on a mathematical representation of a transmission line using three coefficients – K0, K1 and K2. The somewhat limited information on the developer’s website says K0 is associated with the dc resistance of the conductors, K1 is associated with the skin effect or ac resistance of the conductors, which varies with the square root of frequency, and K2 is associated with the dielectric loss, which varies directly with frequency. Unfortunately, there is no information indicating if these coefficients were developed from measurements, derived from manufacturer’s datasheets or obtained directly from cable manufacturers. The program also displays the traditional transmission line parameters (R, G, L and C) but, again, the sources of these data are not given. Table 1 ~ Comparison of Transmission Line Details with Times Microwave Online Calculator. All values are for a line length of 30.5 m (100 ft)
Parameter
Attenuation (dB) Efficiency (%) Delay (ns) Attenuation (dB) Efficiency (%) Delay (ns) Attenuation (dB) Efficiency (%) Delay (ns)
10 MHz 100 MHz Times Times TLD TLD Microwave Microwave RG‐58/U (Belden 9201) 1.4 1.056 4.6 3.671 72.2 78.411 34.9 42.941 153.94 155.896 153.94 154.633 LMR‐240 (Times Microwave) 0.8 0.754 2.5 2.431 83.8 84.067 56.8 57.129 120.95 122.421 120.95 121.475 LMR‐400 (Times Microwave) 0.4 0.394 1.2 1.265 91.4 91.318 75 74.739 119.53 120.334 119.53 119.841
1000 MHz Times TLD Microwave 15.3 3 153.94
14.855 3.269 154.232
8 15.9 120.95
8.012 15.805 121.175
4.1 38.7 119.53
4.131 38.624 119.684
I compared the loss, efficiency and phase delay calculated by TLD with a manufacturer’s online calculator {TMW} for Times Microwave LMR‐240 and LMR‐400 and Belden 9201/RG‐58/U cable (table 1). There was close but not perfect correspondence for the Times Microwave cables, and there were some significant discrepancies for the RG‐58/U cable. The problem with RG‐58/U is that there are many different types. The Times Microwave calculator only lists one RG‐58/U but TLD lists several brands and types of RG‐58/U, RG‐ 58A/U and RG‐58C/U. One manufacturer, Belden, makes at least three different types of RG‐58A/U, all with slightly different transmission characteristics. Clearly, the user must know exactly what specific type of RG‐ 58 and manufacturer they have. On the other hand, the characteristics of the Times Microwave LMR cables
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are better controlled and understood. I noticed the Times Microwave calculator showed a constant phase delay at all frequencies and TLD showed slight variations. Some of the differences in the comparisons could be due to rounding. TLD displays all calculations to three decimal places and the Times Microwave calculator to one decimal place. It should be noted that transmission parameters associated with ordinary commercial coaxial cables are not given in datasheets with the precision of three decimal places. On the other hand, it often is helpful to retain several decimal places in calculations to reduce the build‐up of rounding errors in higher order terms. A natural question is, which calculation is more accurate – manufacturer’s data or TLD? Without knowing the source of the data, it is impossible to say but I recommend a default or at least a cross‐check to manufacturer’s data. However, TLD appears to provide sufficient accuracy for practical work.
Figure 3 ~ Plot window showing calculated matched line loss as a function of frequency. This window allows the user to compare two cable types, the first (blue trace) chosen from the main window, in this case, Belden 8219/RG‐58A/U, and the second (red) from the Matched Line Loss window shown here, in this case, Belden 8240/RG‐58A/U. This also shows the importance of knowing the exact type of cable being investigated.
TLD goes beyond simple electrical and physical length and loss calculations and allows the user to vary the underlying cable characteristics. It also allows the user to specify source (input) or load impedances and to plot various derived data such as line characteristic impedance (Z0), velocity factor (VF) and loss over frequency for these new values (figure 3). These plots show that cable characteristics can vary considerably over a range of frequencies. The user can then change the parameters to optimize their application. All charts in TLD cover a frequency range of 0.1 to 1000 MHz. Although it accepts lower and higher spot frequencies, I made no effort to determine if the calculations are valid. Lower frequency calculations most
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likely are valid, but simple transmission line models fall apart above 1 or 2 GHz because of complicated electromagnetic effects. The characteristic impedance of a transmission line is simply the ratio of voltage to current at any point on the line when it has perfectly matched terminations. With most coaxial lines, the theoretical characteristic impedance is based only on its physical dimensions and the dielectric between the center and outer conductors. TLD makes it easy to investigate a specific frequency to find the voltage standing wave ratio (VSWR) with respect to the actual characteristic impedance as well as unmatched source and load impedances. This is one advantage TLD has over most cable manufacturer’s calculators. Example: Suppose we have a UHF solar radio spectrometer and would like to make a band‐trap filter for television channel 20 from RG‐58A/U coaxial cable that has a velocity factor of 0.66. We know that a 1/4‐ wavelength transmission line will transform an open circuit at one end to a short circuit at the other. If we connect the open 1/4‐wavelength line to a T‐adapter between the antenna and the receiver, it will suppress signals in a band around the frequency corresponding to 1/4‐wavelength. The channel 20 center frequency is 509 MHz. On the main window select Belden 8259/RG‐58A/U and then click the Freq‐VF‐Len‐WL Conversions button (figure 4). In the new window that pops up, click the Physical Length radio button and enter the Frequency and Electrical Length as a fraction or degrees in the appropriate boxes.
Figure 4 ~ Conversions window. Left: The physical length (grayed boxes) of a 1/4‐wavelength line made from RG‐58A/U coaxial cable (or any cable with a velocity factor of 0.659 at 509 MHz). Right: Using the actual measured trap frequency, the velocity factor of the cable and T‐adapter together is found to be 0.636, about 3% lower than the value originally calculated by TLD for the cable alone. See text for discussion.
The grayed‐out boxes just above the Electrical Length entry boxes show the physical length in Feet and Meters, in this case 97 mm. When we selected the cable type and frequency, TLD calculated the velocity factor for that frequency, but the Velocity Factor can be changed to see its effect on length. The calculations apply to any transmission line with a velocity factor of 0.659 at 509 MHz, not just this particular RG‐58A/U. Just for fun, I cut a section of RG‐58A/U to the length specified less the distance from the BNC connector reference plane to the center of the T‐adapter (figure 5). This worked out to be 90 mm. I did not attempt to adjust for the dielectric in the T‐adapter and simply connected the assembly between the tracking generator output and spectrum analyzer input with a 10 dB attenuator on the tracking generator side to reduce
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reflections. The resulting dip in the response was measured at 491.96 MHz. I then went back to TLD, selected the Velocity Factor radio button in the conversions window and changed the frequency to 491.96 MHz, which lowered the velocity factor by about 3%. Assuming the T‐adapter uses PTFE dielectric, its velocity factor is close to 0.69 and the composite velocity factor of the cable and adapter should be slightly higher than for the cable alone. There are many ways of looking at the difference in measured results compared to calculations. For example, the tolerances in cable manufacturing or specification or calculation of velocity factor could be the culprit. Or, the test cable lengths may have influenced the measurements. Perhaps 10 dB attenuators should have been used on both sides of the trap during measurements instead of just the transmit side. This example shows that 1/4‐wave traps, or any calculated transmission line section, should be measured under conditions of use. However, in this case, the trap probably is wide enough to do the job at the intended frequency 509 MHz. Figure 5 ~ Open‐circuited 1/4‐wavelength coaxial trap filter for 509 MHz (upper‐left) connected to a BNC T‐adapter with the lower connection from the tracking generator through a 10 dB attenuator and the right connection to the spectrum analyzer.
One quirk resulting from the considerable flexibility of this program is that one can set their own trap. For example, the Freq‐ VF‐Len‐WL Conversions button uses calculated values to display physical and electrical length based on the frequency, velocity factor and other conditions set in the main window. The frequency and velocity factor can be changed by the user but once the conversion window appears the other conditions in the main window are fixed. I found it easy to make erroneous calculations if conditions or changes were inadvertent or forgotten. TLD anticipates this by providing a button on the main window labeled “Reset Parameters to Original Values” so the user can quickly get out of trouble. Nevertheless, it is important to confirm the main window settings before using the conversion button. One feature that TLD lacks is a convenient way to vary the transmission line resistance for different temperatures. Most manufacturer data is supplied for a temperature of 25 °C (77 °F). This is a good average temperature for most analyses. However, the interior of a coaxial cable in direct sunlight can rise 17 °C above the long‐term average ambient temperature. In critical applications where higher ambient temperatures prevail, it may be necessary to determine cable loss at temperatures as high as 60 °C (140 °F). Most metals, including copper, have a temperature coefficient of resistance around 0.4% per °C temperature change. For example, if the cable temperature is 38 °C (100 °F), the resistance will increase by about 5% and the loss will increase by roughly the same amount. TLD has no provisions for including connector losses in calculations. However, for the TLD’s native frequency range (0.1 to 1000 MHz), the losses of decent quality and properly installed connectors are negligible. In conclusion, the developer put a lot of work into this program making it is easy to use. I found it sufficiently accurate for most of the cables I compared. Like most software tools that allow the user to adjust underlying data, the achievable results depend on how smart you are about those adjustments.
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TLD users should remember there are a lot of cheap and useless coaxial cables available from vendors all around the world and there is no reliable published data for them. This is discussed in [Reeve‐12]. It serves no useful purpose to do an analysis on a cable type, say RG‐58, and then use an off‐brand or unlabeled brand and expect it to work as calculated. 3. References and links [Reeve‐92] Reeve, W., Subscriber Loop Signaling and Transmission Handbook: Analog, IEEE Press, 1992 [Reeve‐12] Reeve, W., Coaxial Cable Shields, Radio Astronomy, Society of Amateur Radio Astronomers, March‐April 2012 {TMW} http://www.timesmicrowave.com/calculator/ {TLD} http://www.ac6la.com/tldetails1.html Reviewer ‐ Whitham Reeve is a director of SARA and contributing editor for the SARA journal, Radio Astronomy. He worked as an engineer and engineering firm owner/operator in the airline and telecommunications industries for more than 40 years and has lived in Anchorage, Alaska his entire life.
Cartoon by Nick D Kim. Strange‐Matter.net Used by permission
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Improving long time stability of a radio astronomy receiver Christian Monstein Astronomical radio receivers used to observe weak radio sources often suffer from instabilities in the output signal due to ambient temperature changes, which make it impossible to detect even strong celestial sources. Here, I report about a cheap and successful solution based on a wine cooler to keep operating temperature stable within ± 0.1 °C.
Keywords: Callisto, temperature, Allan‐time Recent experiments with our radio telescope showed that it was almost impossible to detect celestial radio sources like Cygnus A due to the fact that the ambient temperature of the receiver and spectrometer changed in temperature in the order of ± 1 °C. The light‐curves of previous observations had fluctuations in intensity three times higher than the received amplitude of Cygnus A. This was caused by changes in amplifier gain and detector sensitivity that were opposite to temperature changes. We found that the higher the temperature, the lower the signal amplitude. Theoretically it would be possible to compensate the light‐ curves with a simple mathematical model based on the measured ambient temperature. Figures 1 through 5 provide details of our experiments to increase the spectrometer stability.
Figure 1~ Example of a typical temperature plot of the observatory hosting the spectrometer. Temperature changes in the order of ± 1 °C directly affect the output of the AD8307 detector circuit in the spectrometer leading to an unacceptable low value of the Allan‐time variance, see figure 2.
Figure 2~ Allan time [SARA (2012)] variance while observing the sky at 1 GHz. Receiver and spectrometer were exposed to changing ambient temperature. X‐ axis shows integration time expressed in seconds, y‐ axis denotes to standard‐deviation of the intensity signal expressed in digits of the analog‐digital converter (ADC). Best sensitivity in this example is given with an integration time of roughly 150 s (minimum of red plot). The straight line with a slope of ‐0.5 is a theoretical model based on purely Gaussian noise distribution. After this time a re‐calibration has to be applied to the whole system.
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Figure 3~ This commercial wine cooler contains from bottom to top: Power distribution 230 Vac, heterodyne receiver 960 MHz … 1260 MHz down to UHF‐range 750 MHz … 450 MHz, Callisto spectrometer [Benz (2004)] and a separate temperature‐humidity sensor. This wine cooler is based on a Peltier‐cooling system in the backplane and a control panel embedded in the front door. This or similar coolers are available from different suppliers for about US280$. Temperature range can be set digitally between 12 °C and 18 °C. All coaxial and control (RS‐232) cables are fed through a hole in the backplane which was closed by Urethane foam after installation.
Figure 4~ Recent example of a typical temperature plot of the receiver combined with the spectrometer inside the wine cooler. Temperature stability is in the order of ± 0.1 °C leading to improved Allan‐time of the spectrometer system. Further improvements are possible but cost probably would increase exponentially with stability requirements.
Figure 5~ Allan time variance while observing the sky at 1 GHz with receiver and spectrometer mounted in a temperature stable wine cooler at 16.9 °C ± 0.1 °C. Best sensitivity in this improved example is given with a larger integration time of roughly 500 s (minimum sigma value of the red plot). The straight line with a slope of ‐0.5 is a theoretical model based on purely Gaussian noise distribution given by the so‐called radiometer equation.
Conclusion Radio astronomical observations of weak celestial sources require high stability of temperature of the whole instrument (preamplifier, receiver, spectrometer and even cables and connectors). Otherwise, recalibration of the whole chain is needed every two minutes or so. Each calibration task is synonymous to data loss and finally leading to wasted observation time. Modern, cheap wine coolers allow keeping the instrument stable within temperature ranges down to ± 0.1 °C. The next step in our improvement plan is to stabilize temperature of the low noise preamplifier in the front end of the radio telescope. It would even allow cooling the preamplifier a few Kelvin below ambient temperature to reduce the noise figure of the front end.
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On the other hand, this also introduces a risk to increase humidity and produce water in the amplifier due to the temperature gradient to the outside temperature. Links: Callisto general information: http://www.e‐callisto.org/ References and further reading [SARA (2012)] Christian Monstein, Allan Time, SARA journal May – June 2012 [Benz (2004)] Arnold O. Benz, Christian Monstein and Hansueli Meyer, CALLISTO, A New Concept for Solar Radio Spectrometers, Kluwer Academic Publishers, The Netherlands, 2004
Cartoon by Nick D Kim. Strange‐Matter.net Used by permission
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Old Tool, New Use: GPS and the Terrestrial Reference Frame By Alex H. Kasprak Flying over 1300 kilometers above Earth, the Jason 2 satellite knows its distance from the ocean down to a matter of centimeters, allowing for the creation of detailed maps of the ocean’s surface. This information is invaluable to oceanographers and climate scientists. By understanding the ocean’s complex topography—its barely perceptible hills and troughs—these scientists can monitor the pace of sea level rise, unravel the intricacies of ocean currents, and project the effects of future climate change. But these measurements would be useless if there were not some frame of reference to put them in context. A terrestrial reference frame, ratified by an international group of scientists, serves that purpose. “It’s a lot like air,” says JPL scientist Jan Weiss. “It’s all around us and is vitally important, but people don’t really think about it.” Creating such a frame of referenceis more of a challenge than you might think, though. No point on the surface of Earth is truly fixed. To create a terrestrial reference frame, you need to know the distance between as many points as possible. Two methods help achieve that goal. Very-long baseline interferometry uses multiple radio antennas to monitor the signal from something very far away in space, like a quasar. The distance between the antennas can be calculated based on tiny changes in the time it takes the signal to reach them. Satellite laser ranging, the second method, bounces lasers off of satellites and measures the two-way travel time to calculate distance between ground stations. Weiss and his colleagues would like to add a third method into the mix—GPS. At the moment, GPS measurements are used only to tie together the points created by very long baseline interferometry and satellite laser rangingtogether, not to directly calculate a terrestrial reference frame. “There hasn’t been a whole lot of serious effort to include GPS directly,” says Weiss. His goal is to show that GPS can be used to create a terrestrial reference frame on its own. “The thing about GPS that’s different from very-long baseline interferometry and satellite laser ranging is that you don’t need complex and expensive infrastructure and can deploy many stations all around the world.” Feeding GPS data directly into the calculation of a terrestrial reference framecould lead to an even more accurate and cost effective way to reference points geospatially. This could be good news for missions like Jason 2. Slight errors in the terrestrial reference frame can create significant errors where precise measurements are required. GPS stations could prove to be a vital and untapped resource in the quest to create the most accurate terrestrial reference frame possible. “The thing about GPS,” says Weiss, “is that you are just so data rich when compared to these other techniques.” You can learn more about NASA’s efforts to create an accurate terrestrial reference frame here: http://spacegeodesy.nasa.gov/. Kids can learn all about GPS by visiting http://spaceplace.nasa.gov/gps and watching a fun animation about finding pizza here: http://spaceplace.nasa.gov/gps-pizza.
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Artist’s interpretation of the Jason 2 satellite. To do its job properly, satellites like Jason 2 require as accurate a terrestrial reference frame as possible. Image courtesy: NASA/JPL-Caltech.
Editors: download photo at http://www.jpl.nasa.gov/missions/web/ostm.jpg
This quiz is harder than it looks http://www.csmonitor.com/Science/2011/1209/Are‐you‐scientifically‐ literate‐Take‐our‐quiz
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Strong RFI observed in protected 21 cm band at Zurich observatory, Switzerland Christian Monstein Abstract While testing a new antenna control software tool, the telescope was moved to the most western azimuth position pointing to our own building. While de‐accelerating the telescope, the spectrometer showed strong broadband radio frequency interference (RFI) and two single‐frequency carriers around 1412 and 1425 MHz, both of which are in the internationally protected band. After lengthy analysis it was found out, that the Webcam AXIS2000 was the source for both the broadband and single‐frequency interference. Switching off the Webcam solved the problem immediately. So, for future observations of 21 cm radiation, all nearby electronics has to be switched off. Not only the Webcam but also all unused PCs, printers, networks, monitors etc.
Keywords: 21 cm, RFI Find the source of illegal RFI We first suspected the RFI source was our own PC, monitor, network or printer. One device after the other was switched off while the spectrum was carefully observed. Moving the telescope up and down and left and right (figure 1) did not help because of many reflections from the surrounding infrastructure. There was no clear maximum detectable that would have helped to identify the RFI source or sources shown in figures 2, 3 and 4. Finally, after a walk around the building, we found a Webcam AXIS2000 that was originally installed for safety reasons to observe the telescope position remotely via a web‐interface. Then I switched off the electric power to the Webcam and the RFI immediately disappeared, and the spectrum showed a quiet and clear background signal as expected from previous observations.
Figure 1 ~ Antenna control application points the telescope (green cross) to the west‐ corner of our building (green area) at azimuth 331.96° and elevation 13.55°. The green area depicts the optical horizon (buildings, trees, bushes etc). The yellow curved line stands for the path of geostationary satellites while the dotted line shows the path of the sun. The sun itself is presented as yellow circular spot. The yellow dashed line at the top and sides marks the safety area for the telescope while the red dashed line marks the area given by the saftey switch, which powers off the telescope motor drives if opened acidentally.
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Figure 2 ~ Two dimensional spectrum of intensity over time and frequency from a Callisto radio spectrometer (with down‐ converter) shows terrible RFI over the entire 21 cm band including two strong carriers around 1412 MHz and 1425 MHz (green horizontal lines on blue background). Within the protected 21 cm radio frequency band I normally expect a smooth, clean spectrum. The left y‐axis shows the channel number while the right y‐axis denotes to the channel‐ frequency. A fixed background is subtracted to better show the spectral details.
Figure 3 ~ Two dimensional spectrum showing 22 minutes of continuous observation with a Callisto radio spectrometer while moving the telescope to the western corner of the observatory and back to the parking position labeled 'clear sky'. The parking position is at 180° azimuth and 45° elevation. Additional broadband noise is observable between 15:44 and 15:49 UTC. The 1425 MHz spectral line also shows fringes in intensity due to interference produced by reflections from nearby conducting infrastructure.
Figure 4 ~ Absolute power spectrum taken with a commercial spectrum analyzer PSA2702 from TTi (Thurlby Thandar Instruments) while the Webcam AXIS2000 was powered. The connection of the spectrum analyzer was at the same position in the signal chain as the spectrometer, about 10 m behind the low noise amplifier. The two cursor positions show signal carriers at 1412.519 MHz (blue) and at 1425.037 MHz (yellow). Both signals are much stronger than any 21 cm line observed in ORION (OMC) or any other star forming region in our own galaxy. So we have to find the source of this illegal RFI as soon as possible.
Intensive testing and checking finally helped to identify the guilty source of RFI – our own Webcam AXIS2000 used for observing the telescope for security reasons. Upon checking the documentation, I discovered that the internal processor of the Webcam is an AMD Athlon clocked at 1412.4 MHz and the DDR3 SDRAM is clocked at 1425.1 MHz. I then switched off the Webcam and we observed an absolutely clean spectrum – even in the center of downtown Zurich – as seen in figure 5. I also could demonstrate at our remote
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observatory that the Webcams produced RFI in the nearby telescopes, especially broadband noise at frequencies
