A montage of my own large collection of various WR-3s and prototypes built since 1991 and a shot of me in the eastern Mojave Desert listening to sunrise whistlers in March 2003.
Photo of me atop Mt. Vision - Pt. Reyes National Seashore 21 January 2004 - recording whistlers live on WR-3 - photo by David Monaghan
Natural VLF Radio signals were the first radio signals mankind first heard, beginning in the early 1880's reportedly on long telephone lines. They are considered the "primordial radio" sounds of our incredible planet Earth's huge magnetosphere. They may be also referred to as "space-weather sounds". All describe a great variety of fascinating radio signals now easily monitored once you find a quiet listening site devoid of local electrical interference - specifically, alternating current (mains) power-lines. Then you're on your way to enjoying a new realm of nature and radio-science--and a truly aesthetic one at that!. If you have not yet heard what these signals of Earth sound like, please check out the Soundbites Page(s)
Natural-radio emissions vary in characteristics from place to place at any given time when they are occurring. Whistlers occurring loudly in one location may sometimes sound considerably different at another location just several hundred miles or kilometres apart, and chorus or "risers" may be head in one location (especially in more northern locales) while whistlers (fallers) are being heard strongly in another locale (usually more southerly). Thus, the natural radio sounds you may hear near your home location will differ somewhat from somebody elses, making for interesting comparisons. This is why it can fascinating to coordinate with a friend or collegue with simultaneous listening
Secondly, the variety of natural radio emissions is infinite - there are the "common" sounds you can hear with a receiver, but sometimes, surprising "uncommon" sounds to receive. This is more so as we are within solar-maximum over the years 2000 - 2002, and predicted maxima of magnetic storms in 2002 to 2004. Remarkably, though the intensity of aurorae drop off during solar-minimum years, the magnetosphere is still extremely active producting aurora in the Far North (Canada, Alaska, Iceland, Northern Europe and Russia), and the common whistler still are audible througout the mid-latitudes easily, on nights when they do occur.
The Model WR-3 is a sensitive, hand-held E-field" receiver designed for monitoring fascinating natural VLF radio phenomena in the 0.2-10 kHz (200-11,000 Hz) radio frequency range, where for the most part, no man-made radio signals exist.
Down at these low radio frequencies, you can hear a great variety of naturally-occurring ELF/VLF radio signals , such as "Whistlers" "Tweeks" "Auroral Chorus" "Dawn Chorus" "Risers" "Wavering-Tones," "Hiss," and other intriguing radio phenomena which this receiver has been specifically designed to receive.
Natural ELF/VLF radio emissions, first heard on long-distance telegraph lines in the 1880's, are produced by Earth's lightning storms, Auroral displays, and Earth's magnetic envelope surrounding the planet, called the "magnetosphere." Since the majority of natural VLF radio signals audible at Earth's surface originate from within the magnetosphere as "plasma-waves," they are very sensitive to geomagnetic conditions and can tell researchers a great deal about what is happening with the Earth-Sun environment, as an amazing amount of Natural VLF Radio emissions (at audio frequencies) are generated during magnetic storms. All of these radio phenomena (whistlers, chorus, etc.) are audible most strongly in mid-to-upper latitudes of the northern or southern hemispheres, between 30 to 60 degrees north or south.
When geo-magnetic storms happen, they also cause Aurora (the Northern and Southern Lights) which in turn generate the musical, bird-flock tweeting or bizarre dog-bark sounds of "Chorus," which you can hear very well with the WR-3/WR-3E - generally at dawn-periods throughout the mid-latitudes, but often extending into mid-morning if you are actually within the auroral-zone such as in Alaska, central/northern Canada, northern Europe, Antarctica. If you live far enough north or south, you can watch Aurora dance in the sky and also LISTEN to their interesting VLF radio sounds with these receivers -- I first observed this amazing correlation at 4 in the morning in Alberta, Canada in September 1993, during a pulsating-aurora display. Movements of the aurora (especially the pulsating type occurring past the peak of typical auroral displays) are usually synchronized with their changing VLF radio sounds--it's amazing! Those fortunate to be in areas where aurora is frequent will enjoy great DAYTIME natural VLF radio sounds too.
Sunrise and an hour before and afterwards can be a rewarding time to listen for chorus during magnetic storms, which is why it is often referred to as "The Dawn Chorus." Dawn Chorus can take on the sounds of bird-flock tweeting or lower pitched sounds similar to dog or seal barks. "Hiss" and "Wavering/wandering-tone emissions" (or a combination of the above phenomena) can also be heard during some magnetic storms with the WR-3. Many examples of this phenomena are presented in the audio-files section on spaceweathersounds.com
Lightning storms have their own incredible effect on Earth's magnetic field. A million lightning strokes occur worldwide every day from thousands of storms in progress at any given time. Lightning-stroke radio energy is greatest between below 10 kHz and triggers natural radio sounds called "Whistlers." This is because lightning-storm radio energy is capable of being ducted within Earth's magnetic field from one polar hemisphere to the opposite hemisphere; undergoing an effect researchers call "dispersion" as well as being amplified and sustained during its long 25,000 mile journey between the hemispheres. This unusual form of radio wave propagation creates falling-note sounds called "Whistlers." Whistlers can range in sound from very pure and flute-like notes or sound growly, swishy, and breathy. On some nights and mornings (the best time to listen for whistlers is after nightfall), there can be a whistler every second (or even more)!
The WR-3 has been designed to make monitoring of natural radio as easy and convenient as possible, as thereceiver requires only a short 30 to 60 inch/0.5 to 1 metre long whip-antenna (BNC-type base mount). The WR-3 has a headphone jack for "mini-stereo" style stereo headphones (1/8-inch/3.5 mm plug). Since most listeners already have their own preferred kind of headphone, headphones are not supplied, thus we can keep the price lower.
Because the WR-3 converts the 0.2-11 kHz ELF/VLF frequencies directly to audio signals in the headphones, it requires no tuning, mixer or i.f. circuitry like broadcast receivers. The WR-3 has one control knob: audio GAIN and Power ON/OFF. A telescoping whip antenna mates tightly onto a male BNC-type connector. The ultimate in portability, this receiver (with antenna detached) fits into your shirt pocket.
A very detailed Listening Guide is included with each receiver on a compact-disc in both HTML format for web browsers, and also in PDF for viewing with the Adobe Acrobat Reader (available for no-cost at www.adobe.com). Additionally, both versions can be viewed online and printed or downloaded. The Listening Guide gives a good overview of "Natural Radio" listening and has a list of additional references and scientific publications where you can refer to if interested in reading further about natural radio phenomena.
A 7-plus HOUR MP3 compilation CD "Auroral Choruses I to III" CD is full of an immense variety of examples of natural radio phenomena and is included with each WR-3 receiver shipped, or it can be ordered alone. Full details of this CD are in the Auroral Chorus CD Page.
Stephen P. McGreevy, N6NKS, Aug. 2006
S. P. McGreevy Productions
P.O. Box 928, Lone Pine, CA 93545-0928 USA
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