|Participate in NASA joint coordinated experiments between the space shuttle and volunteer listeners on the ground. These space physics and ionosphere radio experiments are conducted to help us better understand the Earth's natural electrical environment. The Soviet Union conducts similar experiments under their project INTMINS. Participation in INSPIRE and INTMINS is open to volunteers of all nations.|
|A primer on the theory of electrically small loop receiving antennas published on the Longwave Club of America web site. This document rigorously derives the response of a receiving loop under conditions where the loop is very small compared to a wavelength, and operated as a broadband receive antenna below resonance such as in ULF, geological exploration and geomagnetics. Also refer to this handy diagram of loop shapes and aperture factors.|
|Octoloop receive antenna for 0.00003 MHz to 0.2 MHz. Yes, thats right, your ears cover most of that range, which makes trivial receiver designs possible. Complete construction details of the OctoLoop were published HERE on the LWCA web site and were also published in The Lowdown, the journal of the Longwave Club of America. This cheap and easy 50 turn shielded loop design is great for nulling the nasty noise which plagues the bands below 0.5 MHz. I have used it to recieve airport beacons over 2000 miles away, and to listen to natural radio even in suburban areas. This loop antenna is highly balanced and shielded to yield deep directional nulls, which allows a noise or interference source to be nulled out of the receive signal. New 200 turn version includes tickler windings for those who like to experiment with tuning and regeneration.||Due many requests, here is a wiring diagram as well. The number of conductors is not important. Also see 200 turn version for alternative hookups which allow tuning and/or regeneration.
Also see original magazine article for construction notes and tips.
|SpooLoop receive antenna for 0.00003 MHz to 0.2 MHz. This quick and dirty receive loop design was a last minute compact, rugged antenna to be tossed into an overnight bag for an unexpected business trip near the South Pole. The antenna works better than expected, so here it is.|
|The LF LNA, an Ultra-low noise, high CMRR and excellent balance are key features of this receive preamplifier covering DC to 300 kHz. This very simple circuit uses a biomedical instrumentation amplifier with an equivalent input noise of only 0.009 microvolts per root Hz, and a 1/f noise below 0.28 uV rms total from 0.1 Hz to 10 Hz.. Excellent companion to the OctoLoop or SpooLoop, this preamp and a Radio Shack pocket speaker amp can hear magnetic ripples from a mechanical watch ticking a few meters away, and an automobile a mile away.|
|The MK IV ELF/ULF software tuned receiver. This is a work-in-progress; results from my Mk IV design encourage me to proceed further. The Mk IV uses an analog front end to condition the signal, a dvm with serial interface to acquire the data, custom software to make a Microsoft .wav file, and shareware to post-process the files. The LONGWAVE BBS (706-672-0360) has some design info on my Mk III and my Mk IV receivers. This highly sensitive front end for a centertapped loop combines the ultra-low noise preamp with passive and active filtering.|
|This 60 Hz passive notch filter improves the dynamic range of DSP and SSP receivers by preventing overload of the analog front end by 60 Hz hum. Passive design with DC coupling incurs no error, no increase in noise floor, and no degradation of dynamic range.|
|Cloud Charge Monitor||Easy Homegrown electrometer by Charles Wenzel can detect changing charges of passing clouds. Simpler than a field mill, no moving parts, build it in a weekend !|
In the range of 0 to 10 Hz, we 'hear' or sense waves from the internal groans and creaks of the Earth, the solar wind howling around the Earth's magnetosphere, magnetic storms, and a host of unknown phenomena. Although these are infrasonic, below human hearing, you can speed up a recording to bring them within range of human hearing.
One of the hottest research topics in this part of the electromagnetic spectrum is the possibility of earthquake precursors that could provide an early warning and save lives. The National Earthquake Information Center at the United States Geological Survey provides this and other near-real time maps, maintains searchable databases and other resources, a veritable Mecca of seismology.
Fields and Waves in this region of the spectrum include magnetometers and electrometers for magnetic and electric fields to DC, and seismographs and gravimeters for mechanical and gravity waves.
Altair's Favorite Natural Radio Links
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