697	2007-05-03 07:35:24	mrl_msts	Northern Lights
Message	Date	From	Subject
Hi, I've just joined, wondering if anyone might be willing to advise me on building a receiver that would be tunable through 1-100 Hertz? The goal is to film the Northern Lights, using this receiver too sweep through these frequencies in search of Borealis induced RF noise to accompany the image. Any help would be appreciated. Thank you, Zoe
698	2007-05-03 14:30:17	Ed Almos	Re: Northern Lights
This would be an interesting challenge. As a first principle I would not attack this as an RF project. It would be difficult if not impossible to have an oscillator 1Hz to 100Hz away from the IF frequency feeding into the first mixer of an IF strip. A better solution might be to use an audio amplifier with a variable low-pass or band-pass filter
699	2007-05-03 14:43:50	arv evans	Re: Northern Lights
Zoe A number of years ago Arthur Stokes "invented" a Gyrator Tuned VLF receiver for this very purpose. You can find references to his work and a schematic and PCB layout at: http://www.aavso.org/observing/programs/solar/gyrator.shtml The design uses op-amps as synthesized inductors for VLF use. Good luck, Arv - K7HKL Ed Almos wrote: This would be an interesting challenge. As a first principle I would not attack this as an RF project. It would be difficult if not impossible to have an oscillator 1Hz to 100Hz away from the IF frequency feeding into the first mixer of an IF strip. A better solution might be to use an audio amplifier with a variable low-pass or band-pass filter
700	2007-05-03 15:35:14	Kevin Purcell	Re: Northern Lights
Why the frequency range? You are going to find a lot of interference at 60Hz. At that low frequency playing it back in real time won't sound that interesting. Sure you don't want to listen in the VLF (3 to 30kHz) range (for whistlers and the like?) <http://en.wikipedia.org/wiki/Extremely_low_frequency> <http://en.wikipedia.org/wiki/Super_low_frequency> <http://en.wikipedia.org/wiki/Ultra_low_frequency> <http://en.wikipedia.org/wiki/Very_low_frequency> <http://www.vlf.it/> is a great site for this. <http://en.wikibooks.org/wiki/Electronics/VLF-reception_with_the_PC> For example, for VLF <http://www.vlf.it/ewer3/spectrum1.html> <http://www.northcountryradio.com/Kitpages/elfrcvr.htm> or for ELF (0Hz to 30Hz) <http://www.elfrad.com/> <http://www.elfrad.com/dc30.htm> Antennas can either be very short E field probes, inductive systems or at the lowest frquencies a ground dipole (that latter needing a lot of space ... tens of km for military submarine comms) <http://en.wikipedia.org/wiki/Ground_dipole> A lot of LF/VLFers use computers to take input from external preamps wired up to large inductive antennas. You'll probably need to take this approach to recording on a computer too. I didn't know there were amateurs down below 10kHz with PSK31 :-) <http://homepage.ntlworld.com/lapthorn/earthmode.htm> <http://www.qru.de/vlf.html> > The first two-way QSO between DF6NM and DJ2LF on 8950 Hz was > conducted August 19, 2000 over a distance of 200m ("... can you > hear me?" "NO" - "can you see me?" "YES": that's amateur radio on > VLF ...) using earth electrodes on both sides. Now that's EMRFD :-)
701	2007-05-03 15:50:41	GreatLocoChase@ai...	More Northern Lights
Thank you so much for all your information. Perhaps I should have simply asked what would be the best receiver to find these noises, eh? Has anyone any experience with this type of audio tracking? Has anyone the time to help in finding (and constructing) such a device? My specialty is Cinematography, and could use help in the 'sound' end of this project. Thank you, Zoë Topper Check Out the new free AIM(R) Mail -- 2 GB of storage and industry-leading spam and email virus protection.
716	2007-05-04 17:45:40	kb3wk	Re: Northern Lights
Zoe: Here's a thought. During the late 1960's and early 1970's, there was a researcher at the University of Alaska at Fairbanks who was interested in the emanations of the Northern Lights. He was particularly interested in the frequency range you mentioned, and used acoustic microphone arrays for pickup. Unfortunately, I don't remember his name, as I met him only once. But, you might be able to find something on the search engines using the terms ["Fairbanks, Alaska" "University of Alaska" aurora]. This fellow would probably have a descripti