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G0FTD > VLF 18.03.05 02:06l 51 Lines 2215 Bytes #999 (0) @ WW
BID : 5C9881G0FTD
Read: GUEST DF7PS DJ2RT DG9NBR DL2SFO
Subj: VLF receivers (intro)
Path: DB0FHN<DB0THA<DB0ERF<DB0FBB<DB0IUZ<DB0GOS<ON0AR<ON0AR<GB7CIP<GB7SXE
Sent: 050317/1700Z @:GB7SXE.#38.GBR.EU #:25165 [Hastings] FBB7.00i $:5C9881G0FT
From: G0FTD@GB7SXE.#38.GBR.EU
To : VLF@WW
The following text is taken from P. McGreevy's original article.
I have used it as an introduction to VLF and the world of VLF whistlers.
The full text, circuit diagram and MP3 recordings have been sent in a 100kb
zip file suitable for amateur packet radio transmission @ww.
It's in 14 parts at 9kb each.
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Whistlers are magnificent sounding bursts of ELF/VLF radio energy initiated
by lightning strikes which "fall" in pitch. A whistler, as heard in the
audio output from a VLF "whistler receiver," generally falls lower in
pitch,
from as high as the middle-to-upper frequency range of our hearing downward
to a low pitch of a couple hundred cycles-per-second (Hz). Measured in
frequency terms, a whistler can begin at over 10,000 Hz and fall to less
than 200 Hz, though the majority are heard from 6,000 down to 500 Hz.
Whistlers can tell scientists a great deal of the space environment between
the Sun and the Earth and also about Earth's magnetosphere.
The causes of whistlers are generally well known today though not yet
completely understood. What is clear is that whistlers owe their existence
to lightning storms. Lightning stroke energy happens at all
electromagnetic
frequencies simultaneously that is, from "DC to Light." Indeed, the Earth
is literally bathed in lightning-stroke radio energy from an estimated
1,500 to 2,000 lightning storms in progress at any given time, triggering
over a million lightning strikes daily. The total energy output of
lightning storms far exceeds the combined power output of all man-made
radio signals and electric power generated from power plants. Whistlers
also owe their existence to Earth's magnetic field (magnetosphere), which
surrounds the planet like an enormous glove, and also to the Sun.
Streaming from the Sun is the Solar Wind, which consists of energy and
charged particles, called ions. And so, the combination of the Sun's Solar
Wind, the Earth's magnetic field surrounding the entire Planet
(magnetosphere), and lightning storms all interact to create the intriguing
sounds of whistlers.
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