A BEGINNER'S GUIDE TO NATURAL VLF RADIO PHENOMENA

By Michael Mideke
Ragged Point, CA

Fifth part:

WHISTLER HUNTING

Once the receiving system is working properly and you've gotten accustomed
to setting it up, the time has come for more serious whistler hunting. The
questions are 'When?' and "Where?'

WHEN? Whistlers and emissions may be heard at any hour of the day or night
but odds are best around dawn. Atmospheric and manmade noise are usually
at their lowest then and the magnetosphere seems to be especially sensitive
as well. If you begin listening by the first glimmer of daylight and
continue until the sun is above the horizon, chances are fairly good that
you'll catch the day's best activity. But this is only a general rule.
Sometimes nothing will happen at dawn and there will be a peak of activity
at sunset or a few hours after dark.
Whistler and emission activity seems to occur in runs of about 3 to
7 days. There are also periods of days and even weeks with very little
activity. At one extreme: more than 20 whistlers a minute. At the other:
less than one per hour or none at all.
VLF emissions often appear during or shortly after magnetic storms.
Magnetic storms are produced by interactions between earth's magnetic field
and particles ejected from regions on the sun undergoing violent activity.
Sometimes the activity persists through the sun's 27 day rotation period.
This can lead to terrestrial magnetic storms and VLF emission events that
follow the periodicity of roughly 27 days. Whistler activity also tends to
be especially interesting during and after magnetic storms. Long
spectacular echo trains are most common at such times.

WHERE? Locally speaking, the place to go is as far as you find it
practical to get from AC power lines. Bear in mind that diminishing
returns are involved here. If you're a kilometer from power lines you'll
have a moderate hum level unless atmospheric noise (lightning static) is
very strong. Doubling the distance to 2 kilometers will make a quite
noticeable improvement as will doubling the distance to 4 kilometers. When
you reach the point where you are unable or unwilling to go twice as far as
you've already come it's time to unpack the equipment and do some listening!
Surprisingly good sites can often be found along public roads.
Look for new roads and scenic routes that have been built away from power
lines. Seek out rough terrain and complex shores that tend to separate
roads from power lines. Elevated scenic outlooks sometimes diverge from
the power lines. Even 1/2 km can make a big difference.
If you're into mountain climbing or backpacking, the place to
listen is wherever you feel line stopping. Overnight camps are probably
best because they get you set for the dawn window. If you have access to a
boat and even a medium size body of water, by all means give it a try. Use
a whip antenna with its base at least a couple of meters above the water
(or the boat's structure if it is metal) and ground the receiver with about
30 meters of wire in the water. Excepting running lights and any other
apparatus required by law to be kept on, turn off all electrical systems
while monitoring.
In general, whistler reception is best at middle geomagnetic
latitudes and worst in the equatorial regions. Whistlers and emissions can
certainly be heard in fair number anywhere in the US. There do appear to
be differences in the character and occurrences of whistlers heard in
Eastern and Western North America. Amateur observations could readily
address questions of how reception differs between the two coasts and how
either coast may differ from mid-continent. While low latitude (below 20
degrees geomagnetic) reception of VLF phenomena is a good deal more
challenging than reception at middle and high latitudes, this also
represents an area where relatively little research has been carried out.
Patient investigation of the tropical. VLF environment might yield some
interesting surprises.
If you're fortunate enough to live some distance from the power
grid, you could be in the enviable position of having first-rate listening
with all the comforts of home. The receiving system outlined here is
adequate to get you started but later you may want to go to a large loop
system that can null either the distant power lines or your household's
electrical noise. (With careful selection of the loop's location, you can
do both.)

RECORDING

You don't have to record the VLF phenomena you hear, but if you
don't, who's going to believe your wild tales of strange sounds overheard
while everyone with an sense was sound asleep? Very little research can
be accomplished in the absence recordings.
Unless quality portable reel-to-reel or digital tape equipment is
available, the best way to get into whistler recording is with standard
audio cassettes. Any cassette recorder having an external microphone input
should work. Inexpensive machines tend to generate more noise and
distortion than expensive recorders. Machines whose recording level is
controlled automatically (practically all inexpensive recorders) tend to
exhibit audible gain "pumping" in response to sferics. If the sferic
density approaches the ALC (Automatic Level Control) time constant, the
recorder will be effectively desensitized by transient peaks. So it is
best, though by no means essential, to use a recorder that has manual level
control and/or an input attenuator. In general it is best to leave peak
limiters off for VLF recording - saturation by transient peaks costs less
data than the post-peak desensitization imposed by a limiter. However, in
monitoring 'live" reception, a limiter at the monitor input or output can
be a real ear-saver.
I've had quite satisfactory results with Marantz PMD 430 recorders.
At around $450, they represent about the last step before spending a lot
more on "professional" equipment. A key feature on this machine is the
third head, which allows real-time monitoring of what is actually going on
tape - instant comparison between input and output for optimum adjustment
of receiver and recorder. Monaural Marantz machines cost less and work
fine, though you sacrifice the convenience of 2 channel operation by going
mono. If you can possibly afford a 3-head machine, you'll find it well
worth the price. On the other end of the scale, I've gotten usable tape on
a recorder that cost under $30 at a Radio Shack sale.
Improved dynamic range and frequency coverage can be had with
professional 1/4" tape equipment. Nagra is probably the best choice - but
even used machines cost thousands of dollars. If your recorder is to be
used exclusively for whistler work, it should be modified to provide flat
frequency response. This will reduce problems with Omega and MSK overload,
permitting extended high frequency coverage.
The Sony "Walkman" digital audio recorder is now around $650. 1
have no direct
experience with this technology but in theory its extended frequency
coverage and dynamic range should bypass many of the problems associated
with analog recording of VLF phenomena.

RECORDING HINTS - Take spare batteries. Reserve used and questionable
batteries for flashlights. Since you are going to a lot of trouble and
some expense to record VLF phenomena, invest in good tape. This doesn't
necessarily mean the most expensive tape you can find, but avoid the
el-cheapos that are subject to mechanical failure and oxide shedding. I
use TDK SA (Type II, chrome) tapes. They seem to be a little less
vulnerable to high frequency distortion than quality "Type I" low bias
tape. If your recorder is designed operate only with "Type I' tape, use
it. "Metal" tape appears to provide no significant advantage over
"Chrome". Unless there is an urgent need to produce very long continuous
takes, don't use cassettes longer than 90 minutes. If you do wind up with
longer cassettes, dub them immediately to 60 or 90 minute tapes, using the
gentlest playback machine you can find.
If your recorder offers a tape noise-reduction system, don't
automatically turn it on for VLF work. In my experience.(limited to Dolby
B and DBX) the noise reduction simply introduces distortion. VLF is rarely
quiet enough for the noise level of good tape to be a factor but Omega
pulses modulating a noise-reduction may ruin otherwise good recordings.
Label cassettes and cassette boxes. Keep a log that includes the
date and time of each take, along with remarks as to contents of the
recording. It is extremely helpful to make a voice announcement at the
beginning of each take, giving tape number, tape side and the sequential
number of the take on that side. Example: Tape 26, Side A, Take 4. Or
more simply, just- 26 A 4. You may think at the time you'll surely
remember what you're doing, but will this really be the case a few
sessions later? I experience great frustration when people send me field
recordings that lack voice announcements between takes, forcing me to take
great care to find the transitions from one take to the next and to keep
count of all the takes so that I can be fairly sure that what I'm hearing
corresponds to the notes I'm reading!
If you plan to dub and edit your field recordings you should aim
for capturing the widest frequency range the system allows. You can take
your time getting the sound you want through equalization during dubbing -
the more you get on the original tape the more you have to work later. If
the field recording is to be the end product, it makes sense to manipulate
frequency response to emphasize the subject. If the recording is destined
for spectrum analysis, don't mess with it - just go for as broad and flat
as possible.
It is a good idea to log dates and times in UTC (Universal Time,
Coordinated) rather than local time. This practice avoids ambiguities that
can be terribly frustrating to anyone subsequently working with the
recordings. It also means that your data can be easily examined in the
context of other geophysical records kept in UTC. Where whistler recording
is concerned, for all practical purposes UTC is the same thing as GMT
(Greenwich Mean Time).
If you have a portable short-wave radio, it is always possible to
find out the UTC time by tuning to stations WWV and WWVH on 2.5, 5, 10, 15
or 20 MHz. Time is announced on the minute and one or more frequencies are
usually readable.
If you use a stereo recorder, you can run WWV on one track to
provide an accurate time reference. Alternatively, if you are getting at
least one 10.2 kHz OMEGA on tape, all you need is a WWV announcement on the
head of a take. OMEGA dashes provide super-accurate markers as long as the
tape is rolling. If you decide to use a two channel system. run tests to
make sure there is no audible "bleedthru" from one track to the other.
Also check for head misalignment by recording completely different material
on the left and right channels of your field recorder. Then playback on
a couple of good home machines to make sure their heads are tracking with
your recorder. If the field recorder fails this test have it adjusted or
refrain from two channel recording - use only one track or put the same
information on both tracks.

When I find something especially unusual or interesting happening
on VLF, I try to get the WWV announcement at 5 minutes past the hour and
run tape of the VLF event for at least a minute thereafter. This
particular time is chosen because at 5 past each hour, recorders on ELF/VLF
receivers in Greenland, New Hampshire, Italy, California, Japan, New
Zealand and Antarctica automatically roll to capture a minute of whatever
is happening from 10 Hz through 32 kHz. This is part of an ongoing survey
of radio noise conducted by Stanford University. I got into the 5 minutes
past the hour routine while making site sensitivity comparisons with the CA
receiver.
The Noise Survey receivers are not particularly sensitive or free
of manmade noise, and they are very widely separated. Where weak VLF
phenomena are concerned, they are probably of little use. But the network
does establish a minute in each hour that is known to be monitored, and I
urge amateur observers to take advantage of that minute. Don't necessarily
stop recording at 6 past the hour - just get WWV at 5 past and run tape
until you have a representative sample. This procedure improves the
chances of getting simultaneous recordings. Simultaneous data are far more
useful than scattered hunks of random data.

SPECTRUM ANALYSIS - It is possible to tell a great deal about natural radio
phenomena just by listening to them. A practiced listener will notice and
describe things that utterly amaze the beginner. Much valuable data has
been generated by trained listeners painstakingly logging the contents of
recordings. But when it comes to measuring complex variations of signals
immersed in a noisy interactive environment, the ear is a limited
instrument. The whistlers won't sit still, there is nothing to hold on to!
What is needed is some way to reduce these fleeting events to graphic
representations that will sit still to be measured.
In the early 1950s. Owen Storey (then a graduate student at
Cambridge University) felt this frustration so keenly that he built a
primitive spectrum analyzer which was capable of creating frequency vs.
time plots on a strip chart recorder. In present day terms this was an
extremely low resolution instrument, but it was good enough for Storey to
define the essential characteristics of whistlers. In so doing, he also
defined the course of much of the research that has followed. Storey's
tools were quickly made obsolete by a new generation of instruments
designed for the analysis of speech characteristics. These devices, like
Storey 's depended upon passing the signal through a comb of narrow filters
- but instead of actuating pen and ink, the new machines left their mark on
a moving strip of 35 mm photographic film or paper, each filter controlling
a light source focused on a narrow section of the passing film.
In recent years VLF spectrum analysis has been revolutionized by digital technology. Now anyone with a sufficiently powerful personal computer can produce quite satisfactory frequency VS time plots (MacRecorder(tm) calls them "sonograms') from
whistler recordings. MacRecorder(tm) is a product of Farallon
Computing, Inc. It uses an 8 bit analog to digital converter in
conjunction with software to perform a variety of audio frequency analysis
functions: waveform displays, frequency vs. amplitude plots and frequency
vs. time plots. Several sound manipulation and editing functions are also
included but these have little application to whistler work. Lack of an
on-screen time scale and an expandable frequency scale is
frustrating, but at less than 1/10th the cost of competing products,
MacRecorder(tm) is worth a little hand labor. List price is around $250,
with substantial discounts available. A new version is due in 1992. While
many MacRecorder(tm) functions will work on a Mac Plus or Classic, the
MacII is the smallest machine that will support sonograms. The smaller
computers can produce what Farallon calls "spectrograms". These are
frequency VS amplitude plots, with time incorporated as the "Z axis". They
are not particularly useful for the interpretation of whistler type data.

Note from LoScrittoio: Nowdays you can look a many different software -Mac and Windows based- to perform spectrogram. Here a good site to realize how Natural Radio may appear: http://www.triax.com/vlfradio/natradio.htm

Different organizations and authors use the words "spectrogram", "
sonogram" and "sonograph" with various and sometimes conflicting meanings.
When you encounter these terms it is a good idea to double-check on their
utilization.

THINGS THAT CAN GO WRONG - Troubleshooting lists are always frustrating,
and I'm sure this one is no exception. But it does cover many of the more
likely problems. It MIGHT help solve something in a hurry!
Start by asking yourself some basic questions: Has each element in
system worked in the past? (Don't forget cables and clipleads.)
Do monitor, recorder and receiver work on their own? Have these devices
previously worked properly when connected together? Try to localize the
problem but remind yourself that your assumptions may lead you upstream or
downstream of the real difficulty.

NO OUTPUT REGISTERS ON MONITOR OR RECORDER.-

1-Power off.
2-Battery dead or disconnected.
3-Connector not connected or connected to the wrong thing.
4-Damaged cable or connector.
5-Mechanical failure: open connection or short circuit.
6- Failure of electronic component.

FEEDBACK (HOWLS, SQUEAKS, SQUEALS):

1-Monitor, recorder, speaker, headphones or associated leads too close to
antenna.
2-Ground missing or inadequate.
3-Bad connection to or in antenna.
4-Gain at monitor or recorder too high.

DISTORTION IN MONITOR OR RECORDER:

1-Excessive input level to recorder or monitor.
2-Excessive input to receiver.
3-Low battery.
4-Overloading from out-of-band signals.
5-Partial failure of connection or component.

HUM, BUZZ:

1-Too close to power lines, a generator or running vehicle.
2-Pickup from recorder motor.
3-Antenna too close to clock, motor or digital device.

VOICES, MUSIC:

1-Overload from Am or SW Broadcast signals.
2-Detection by rectification in antenna or ground system.
3-Pickup of audio frequency from nearby radios, entertainment systems or
telephones.

TONES(ABOUT 1 SEC. LONG AT FREQUENCIES BELDW 10 KHZ)

1- Overload from OMEGA (Nowdays Omega are turned off).

BURBLING SOUNDS:

1-Overload by MSK (Minimum Shift Keying) from military VLF -stations.

TICKING (10 HZ RATE):

1-Overload or detection in antenna or ground from 100 kHz Loran-C
radionavigation.

RECORDING DISTORTED, MONITOR CLEAN:

1-Overload of recorder @ out-of-band signals.
2-Recorder batteries failing.
3-Incorrect tape bias.

SCRATCHING SOUNDS, WIND NOISE, INSECT NOISES:

1-Antenna rubbing its supports, moving in wind or somehow picking up signal
from flying insects. The shorter the antenna the more of this sort of
interference you'll experience. Its not a defect so much as a fact of life.

CURING DISTORTION AND OVERLOADING: First, try reduced setting of receiver
output level, monitor gain and (if available) recorder level. If this
fails to cure the problem, check or change batteries. If the batteries are
OK, the distortion probably results from excessive input to the receiver.
To reduce receiver input you can shorten the antenna. If pruning
the antenna is impractical, you can insert a variable resistor (500 K to l
M) between antenna and receiver. Set the resistor just beyond the point
where distortion disappears.
If you are working with a loop antenna, try rotating the
loop to a position that reduces or eliminates the distortion. This may
make AC hum worse, in which case it becomes necessary to choose the lesser
evil. If the loop is a very one without a rigid frame, can also try
reducing the loop's size - for instance, make it lower and narrower. If
the loop is of the rigid portable type, in the unlikely event that rotating
it fails to null the overload source you can try tilting it out of the
perpendicular to reduce overall sensitivity.
Persistent overload from local sources may require the installation
of filters or traps designed to eliminate the offending signal. Such
measures should be applied as close as n practical to the receiver's input
stage.
Overload conditions can change with propagation. Overloading is
more likely during night than day and most likely of all around dawn, so it
is good to have a "trimming' option handy.

PRECAUTIONS

Whistler hunting is a fairly safe activity, but there are a few
precautions that should be observed. The dynamic range presented by
natural radio sounds is enormous. Using headphones to listen to static
crashes at high volume levels can cause permanent hearing impairment. So
beware of turning up the level to hear more - it doesn't really help.
Instead, what happens is that the ear-brain system is desensitized, leading
you to turn up the volume some more in a vicious cycle that can take you
over the threshold of ear damage. Instead of turning up the volume, take
breaks from listening and turn the volume down a bit when you put on the
headphones again.

Lightning in the vicinity of your monitoring site poses a hazard to
you and your equipment. If lightning is visible or thunder audible it is a
good idea to disconnect your equipment, ground the antenna and seek
shelter. Don't under any circumstances do antenna work during
thunderstorms!
Stay off of private property unless you have obtained permission to
use it. Always clean up after yourself, removing antennas and ground
stakes when monitoring is completed.

GLOSSARY

Not all of the following radio and radio-geophysical terms appear in the
preceding text. However, you are likely to encounter them in other
references, so they've been included for your convenience. Terms used as
subject headings in the "Basic Guide to Whistlers, Emissions and Associated
Phenomena" have not been repeated here.

ALPHA - A Soviet radionavigation system occupying 3 channels between 11.905
and 14.881 kHz, heard as a series of dashes about 0.3 seconds long.

B-FIELD - The magnetic induction field component of electromagnetic waves.

CONJUGATE POINT - In whistler work this refers to magnetic conjugates which
are the points where a magnetic field line intersects the surface (or some
defined level above the surface) in opposite hemispheres.

COUNTERPOISE - A large conductor substituted for or supplementing an earth
ground connection.

CW- Common term for Morse Code.

DISCONTINUITY - A region where an abrupt change in a quantity occurs. In
the case of whistlers, abrupt changes in electron density within the
magnetosphere and aligned with geomagnetic field lines result in
waveguide-like propagation of VLF radio energy.

DISPERSION --The separation of higher from lower frequencies that produces
whistlers. When electromagnetic waves propagate through absorptive media
such as the magnetosphere and the ionosphere, the highest frequencies
travel fastest, the lowest most slowly. The longer and more absorptive the
path the greater the dispersion.

DIFFUSENESS - The degree to which whistlers depart from a pure tonal
quality to become breathy or "swooshy". Diffuseness is a result of
multi-path propagation slightly offsetting signal components in time.

DUCT - In magnetospheric propagation ducts are assumed to be field aligned
discontinuities in the
plasma whose characteristics produce waveguide-like behavior at VLF
frequencies.

E-FIELD - The electric field component of an electromagnetic signal.

ECHOES - Whistlers reverberating back and forth through the magnetosphere,
becoming progressively dispersed and shifting to ever lower frequencies in
the process. Progressions of several echoes are known as ECHO TRAINS.
Echoes may be more precisely defined in terms of HOPS.

ELF - Abbreviation for Extremely Low Frequency. Formally defined as 300 to
3000 Hz but also frequently used as a generalization or to describe a
different range of frequencies.

GEOMAGNETIC LATITUDE - Approximately, latitude in the geomagnetic
coordinate system as defined by the geomagnetic poles. Tilted about 11
degrees with respect to geographic coordinates.

GEOMAGNETIC POLES - The poles of the best fit centered dipole model to the
earth's magnetic field. Not identical to the magnetic poles.

GROUND-GROUNDING - Connection of a circuit to a large conductor the largest
being the earth.

HERTZ - The frequency of a wave in cycles per second. Abbreviated Hz.
One kilohertz (kHz) equals one thousand cycles per second, one Megahertz
(MHz) is one million cycles per second.

HOPS - In relation to whistler mode propagation one hop is considered to be
a single traverse of the magnetosphere. A one-hop whistler originates in
the opposite hemisphere and has traversed the magnetosphere only once. A
two hop whistler makes two magnetospheric passes, returning to its
hemisphere of origin. In subionospheric propagation, hops are regarded as
the ionospheric reflections between transmission and reception points on
the surface.

IONS - Atoms or molecules that have acquired either a negative or positive
charge.

IONOSPHERE - The region extending above about 60 km to beyond 100 km
altitude, where the concentration of ions is large enough to influence
radio propagation. It is divided into several regions: D (60 to 100 kin),
E (100 to 150 km), F (150 to 1000 km). The F region is further divided
into F1 and F2 regions, with F2 blending into the magnetosphere.

MAGNETIC STORM - Disturbance of the geomagnetic field, usually the result
of interactions between charged particles from solar disturbances and the
geomagnetic field.

MAGNETOSPHERE - Broadly defined this is the region of space within which
the motion of charged particles is controlled by the geomagnetic field.
However, this definition includes most of the ionosphere and common usage
places the magnetosphere's lower boundary around the F2 ionospheric region.

MAGNETOPAUSE - The magnetosphere's outer boundary, extending to a
geocentric distance of about 10 earth radii on the daylight side and beyond
the moon's orbit on the night side.

MSK - Minimum Shift Keying. The modulation mode commonly employed by high
power military VLF transmitters. Produces a burbling sound in conventional
receivers or when overloading a whistler receiver.

OMEGA - A global radionavigation system occupying channels between 10.2 and
13.6 kHz. Heard as a series of 0.8 second dashes.

PLASMA - An ionized gaseous medium.

PLASMASPHERE - An approximately toroidal volume of space surrounding the
earth where the density of the plasma is above about 100 particles per
cubic centimeter, with its outer boundary (the plasmapause) aligned with
geomagnetic field lines whose average equatorial crossing radius lies at
about 4 earth radii.

PROPAGATION - Movement of electromagnetic waves through space. An
important area of space physics research is concerned with propagation in
the near space environment.

UTC TIME - Universal Time, Coordinated. Often referred to as UT. For most
practical purposes identical to Greenwich Mean Time (GMT) or "Zulu" time.

VLF - Very Low frequency. Defined as 3 to 30 kHz but sometimes used with
wildly different frequency ranges.

WAVEGUIDE - A device or physical arrangement which confines the movement of
a wave to a particular path rather than allowing it to radiate in all
directions. In the case of VLF radio waves, a waveguide is formed by the
reflective properties of earth and the lower regions of the ionosphere.

WWV, WWVH - National Institute of Standards and Technology standard time
and frequency transmissions on 2.5, 5, 10, 15 and 20 MHz. UTC time is
given at the commencement of every minute.

RESOURCES

CONSTRUCTION

"GETTING STARTED IN ELECTRONICS" by Forrest M. Mims, III. Radio
Shack (#276-5003) $2.49. A good introduction that will help you to build
and understand the whistler receiver. Other, more specialized booklets by
Mims will help the beginner to learn more about particular subjects. They
are available at Radio Shack.
THE ARRL HANDBOOK FOR THE RADIO AMATEUR. 1216 pages from The
American Radio Relay League. #1670.-$26.50 including postage. 225 Main
Street, Newington, CT-06611. Though primarily devoted to Amateur Radio
communications, the "Handbook" covers radio-electronic theory and
construction practices with depth and clarity.

COMPONENTS

Many mail-order suppliers of inexpensive components have minimum
charges of $50 or more not helpful if you just need a few- dollars worth of
parts. A few sources are more friendly to small orders:

DC Electronics, P.O. Box 3203, Scottsdale, AZ 85271-3203. (Catalog free on
request.) No minimum on prepaid orders- $15 minimum on phone orders. I
think you. can find I everything to build a good whistler receiver at DC,
and lots more besides.

JDR Microdevices, 2233 Branham Lane, San Jose, CA 95124. Catalog - mostly
computer stuff but of components too. Wirewrap wire in 500 or 1000 ft
quantities is usually a good deal here.

Fair Radio Sales, P.O. Box 1105, Lima, Ohio 45802. Great free catalog.
Mostly military surplus, not much in the way of components but lots of test
equipment and military communications stuff.

Longs Electronics, 2601 McDavid Court. Birmingham, AL 35210. Free Catalog.
Good mail/telephone order source for bulk tape, audio equipment, Marantz
recorders.

Mouser Electronics, 11433 Woodside Ave., Santee. CA 92071 and 2401 HWY 287
North, Mansfield, TX 76063. Excellent catalog, almost everything you need
to build anything electronic. High minimum charge but an outstanding stock.

REFERENCES ON VLF PHENOMENA

BOOKS

WHISTLERS AND RELATED IONOSPHERIC PHENOMENA Robert Helliwell, Stanford
University Press, 1965. 343P. A good historical and theoretical
background, with many excellent illustrations. Extensive bibliography.
Out of print, check libraries. Interlibrary loan will get it for you
eventually.

UPPER ATMOSPHERE RESEARCH IN THE ANTARCTIC, Edited by L.J. Lanzerotti and
C.G. Park. Vol. #29 of the Antarctic Research Series, published by The
American Geophysical Union, 1978, ISBN 0-87590-141-7.

VLF RADIO ENGINEERING, A.D. Watt. Pergamon Press, 1967. Extensive chapters
on VLF propagation and atmospheric radio noise fields. Another "one of a
kind" book -that is very hard to find.

PROBLEMS OF ATMOSPHERIC AND SPACE ELECTRICITY, Samuel C. Coroniti, ED.
Elsevier Publishing Co. 1965. The entire proceedings of the Third
International Conference on Atmospheric and Space Electricity. Lots of
good background on thunderstorms and lightning.

ATMOSPHERIC ELECTRICITY. J. Alan Chalmers. Pergamon Press, 1967. Classic
text on the atmosphere as an electrical environment, more good lightning
background.

ARTICLES AND PAPERS

"Whistlers" L.R.O. Storey, SCIENTIFIC AMERICAN, Feb. 1956. pp. 34-37.
Historical background with first-person perspective from the beginning of
the modern phase of whistler research.

"Whistler Waves and the Magnetosphere" Helliwell, THE STANFORD ENGINEER,
Oct. 1982. Good introduction to VLF research, with emphasis on Antarctic
experiments.

"Sun Storms" Jay Stuller, AIR AND SPACE/Smithsonian, June/July 1991 (Vol.
6 N02) P. 50. Nice description of solar monitoring work at the Space
Environment Services Center, Boulder, CO.

'The Dynamic Aurora", Syun-Ichi Akasofu. SCIENTIFIC AMERICAN, May, f989.
Good reference on the structure and functioning of the Magnetosphere.

"Sounds of Natural Radio" Michael Mideke, THE LOWDOWN. June, Aug., Sept.,
Nov. 1989. Feb., March, Oct. 1990. April, June, July 199 l. This is an
ongoing series, combining basic theory with accounts of professional
research and amateur ventures into the realm of natural VLF phenomena.

PERIODICALS (Some of these Periodicals may be out of date)

THE LOWDOWN is a monthly Publication of The Longwave Club of America, 45
Wildflower Road, Levittown, PA 19057. $12 per year. Back issues are
available for $1 each, membership not required for back issue service. If
you are interested in monitoring and communications on longwave, THE
LOWDOWN presents a good cross-section of amateur ties.

Here their site: http://www.lwca.org/

SPELEONICS A quarterly publication by the Communication and Electronic
Section of the National Speleological Society. $4 for 4 issues in USA,
Canada, Mexico. $6 elsewhere. Joe Giddens, P.O. Box 891; Camden. AR 71701.
(Make checks payable to SPELEONICS.) The publication is devoted to
underground communications, radio-surveying and other practical electrical
stuff related to caving. Most of the action is below 100 kHz.

WESTERN UPDATE (The Western Newsletter For MF, LF and VLF Experimenters.)
Available for 29 cent business size SASE's plus $1 per issue or $10 per
year from: Jim Ericson. 226 Charles Street. Sunnyvale, CA 94086-6063.
Mainly by and for "Lowfers' and "Medters" - folks who work with low powered
communications systems in the lower part of the radio spectrum.

THE NORTHERN OBSERVER. Available for $15 (US) per year and 12 self
addressed (not stamped) envelopes from: Herb Balfour, 91 Elgin Mills Rd.,
West, Richmond Hill, Ontario, L4C4M1, Canada. This is a Northeastern
counterpart to WESTERN UPDATE, about monthly, and packed with information.

End of the A BEGINNER'S GUIDE TO NATURAL VLF RADIO PHENOMENA

By Michael Mideke

Please refer to The INSPIRE PROJECT for further information:

http://image.gsfc.nasa.gov/poetry/inspire