• Sferics - Mainly the ubiquitous snap, crackle and pop of lightning all over the earth, this can be heard anytime, anywhere, on frequencies from 1 Hz to beyond 100 MHz. Just tune your AM radio to an empty frequency. Sferics below deserve special mention.
• Tweeks - A modified form of lightning sferic where the electromagnetic impulse undergoes a process of dispersion, and its frequency components become 'smeared out' in time. Commonly sounds like a 'chirp' or 'tweek'. Dispersion results from interaction between the energy wave, the magnetic field of the earth, and the ionosphere (ozone layer). Can be received from 100 Hz to 30 kHz with homebuilt gear, best in an electrically quiet location.
• Whistlers - A sferic which has become dispersed in time to the point of becoming a descending tone. Whistlers are less common, and may be only associated with recently discovered 'upward lightning'. Whistlers can 'echo' back and forth between the northern and southern hemispheres of the earth between magnetic conjugate points, sometimes blending into an eerie and beautiful harmony. Receive techniques same as tweeks.
• Chorus - A sferic normally associated with dawn or aurora especially during magnetic storms. Chorus can sound like whispery voices, or like distant singing of birds, barking animals, surf crashing on a shore, or almost anything. Receive techniques same as tweeks.
• Earthquake waves and precursors - Not sferics, occur at lower frequencies. Gaining credibility in mainstream science as a possible early warning for major earthquakes since the landmark work of Antony Fraser-Smith. Equipment, which can be home built, usually includes a computer to record signals 0.001 to 10 Hz, below human hearing.
• Schumann resonance - A resonant cavity is formed between the ionosphere and the earth. Energy from sferics or other sources may excite this natural resonator to ring at about 8 Hz. Special purpose receiver, can be home built.
• Other Planetary sources - Earth is not the only planet to exhibit a radio personality. Venus is quite similar to Earth, and the four gas giants, Jupiter, Saturn, Uranus and Neptune are natural emitters of HF radio signals. Jupiter's powerful voice may be received on Earth using simple hobby equipment on frequencies around 10 to 40 MHz. The FCC has set aside a 'quiet zone' from 25.55 to 25.67 MHz as one of the radio astronomy listening windows.
• Solar phenomena - The sun is by far the most powerful electromagnetic emitter in our solar system, generating broadband radio emissions, flares, magnetic waves, and storms of electrically charged nuclear particles and ions. These directly cause and/or influence the propagation of electromagnetic waves throughout the known spectrum. The lowest documented electromagnetic solar cycle is about 22 years, or 0.0000000014 Hz. High end frequencies above 100000000000000000000 Hz have been detected.
• Pulsars - Some stars collapse into rapidly spinning cores of extremely dense matter, their intense magnatic fields sweep out charged particles forming an electromagnetic pulse. Typical pulsars rotate about once per second, compared to the earths rotation of once per 24 hours. A faster spinning pulsar is PSR J0835-4510 ( psrb 0833-45 ) is a remnant of the Vela supernova, and rotates at about 11 Hz (period=0.089308556629 s) and sounds to me like something getting slapped by a ceileing fan. The fastest spinning pulsar PSR J1939+2134 ( psrb 1937+21 ) rotates at 642 Hz, (period=0.001557806468819794 s) and its surface at the equator is moving about 14% of the speed of light.
• Gamma Ray Bursts - Satellites designed to monitor nuclear tests received unexpected gamma ray bursts (GRBs) not of earthly origin. In average week, several of these distant, mysterious cosmic events will occur, which for a few seconds will illuminate our planet with gamma rays brighter thatn our own sun. At such great distances the energy at the source must be immense, the entire energy output of our sun over its 10 billion year lifetime is emitted in a few seconds. Even more surprising, the pulse time indicates these distant sources are also much smaller than our solar system.
• Other Cosmic sources - Our universe is filled with many other strange and mysterious electromagnetic voices. Main sequence stars, neutron stars, pulsars, quasars, novae, gas clouds, and even the afterglow of the birth of the universe itself all have their part in the electromagnetic music of the spheres. We don't really know the full range of frequencies, but two high energy (high frequency) events above 10^20 eV have been recorded so far, and the lowest frequency cycles are so slow our technology has not been around long enough to see a complete cycle.
• Human biological sources - The human nervous system uses electricity, and thus creates electromagnetic waves. These waves are usually very weak, but researchers are exploring possible connections with parapsychology in humans, and effects of external sources on living beings. Brainwave radiation can be recorded by instruments at close range in a shielded room between 0 Hz and 100 Hz.
• Marine biological sources - Many species of marine life form use high levels of electricity and electromagnetic waves for sensing, location, communication and defense. Electroreceptive life can sense but not create electromagnetic energy. Dogfish and sharks have receptors called ampullae of Lorenzini, small innervated bulbs attached to a long jelly-filled canal running to an opening in the skin. Detection threshold is only 0.005 microvolt/cm = may detect a flounder at 30 cm, even if buried in the sand. They do not recognize cut up fish buried in sand but will attack a buried cable or electrode. Electrogenic life can generate electromagnetic energy, generally in the frequency band of 1 Hz to 10 kHz. Most Electrogenic fish generate up to 1 volt or so for sensing, location and communication. Here is an Electrical Organ Discharge (EOD) of the Elephant-Nose fish (Gnathonemus Petersi). Jamming of the signal appears when several species of weakly electric fish coexist in the same area, or individuals of the same species. Eigenmannia produces pulses at the frequency 250 - 700 Hz, when another fish interferes, it shifts their frequency (jamming-avoidance reflex). Each fish then has its own private channel. Individuals may be recognized.
  Strongly Electrogenic fish such as Torpedo, Astroscopus, and Electrophorus (electric eel) can generate 10 to 500 volts for defense or to stun their prey.

A true story with a moral:

Epilogue to a true story:

But what if its NOT natural ?

NASA Project INSPIRE

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.

Natural Radio Projects

	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.

• Seismograph Plan - overall scheme of the instrument. Basically a big mass suspended as a (nearly) horizontal pendulum, a coil-and-magnet transducer, plus the signal conditioning and data logging circuits.
• Preamplifier - Low Frequency Low Noise Amplifier (LFLNA) is a high performance, high sensitivity preamp used for many Altair projects.
• BASIC Source Code - controls Radio Shack DVM with serial interface. Logs and plots signals, once per second. Designed to run on low-end PC under DOS.

  ELFRAD

  http://www.sec.noaa.gov/rt_plots/satenvBL_199911300029.gif

Future Projects

• Construction of a water-well seismograph to correlate ambient pressure at -475 ft MSL with my ELF/ULF receivers.
• Construction of Mk V receiver for ULF research, successor to my Mk IV design, and locate the 1/3 Hz mystery signal.
• Construction of an ELF autocorrelator filter to reject ambient interference in urban and suburban areas.
• Detecting radio signatures of earth tremors and meteor showers.

Altair Home Altair's Favorite Natural Radio Links natradio.html, Copyright © September 2001, Altair. EMail altair@altair.org