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DB1QW > VLF 24.06.96 01:50l 366 Lines 20071 Bytes #-10980 (0) @ DL
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Subj: natural radio neueinspielung
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REPOST NOTE!: Capacitor values for C4 and C5 have been corrected! They were
incorrectly 0.047 uF (47 nF), BUT SHOULD BE: 0.0047 uF (4.7 nF).
There was a related 3-part article to this posting, entitled VLF STORY.
originally posted to rec.radio.shortwave 59300-59302 in August 1995.
Re-post note: By this time, those have been archived and are
no longer currently available on the rec.radio.shortwave
USENET group for reading. Please e-mail me if you desire the text of
this article, and I'll send it along to you.
(Editor's note: VLFSTORY.ZIP, containing the entire contents, is
available on the Longwave BBS, or at the following FTP sites:
users.aol.com:/lwcanews/naturadio
ftp.uni-wuppertal.de:/pub/pc/lowfer/lwbbs/naturadio)
Also, note the WWW URL toward the end of this posting for WAV file
availability. I noticed I misspelled the WWW URL, so here it is--
correct at last: http://www-pw.physics.uiowa.edu/mcgreevy/
This URL will be repeated at the end of this posting.
--------------------------------------------------------------------
Use a fixed/mono-width font such as courier 10 cpi or "line Printer"
if viewing in graphical editor/word-processor,
or use Windows Notepad or a DOS text editor such as edit.com.
Thanks to everyone's nice comments! Due to many requests, here is
the schematic to the McGreevy BBB-4 ELF/VLF "whistler" receiver:
REVISED 15 DEC. 1995, WITH LINE-NUMBERS INSERTED IN SCHEMATIC AREA
AND ALSO DUE TO A PART BEING LEFT OUT & INCORRECT PART VALUES (C4, C5)!
-----------------------------------------------------------------------
S. P. McGreevy BBB-4 Naturally-Occurring V.L.F. Phenomena E-field
Receiver ("Whistler Receiver") For Broadband 0.2 to 11 kHz Reception
of naturally-occurring radio phenomena.
(Originally copyright 1993 S. P. McGreevy). spmcgrvy@ix.netcom.com
Snail: Steve McGreevy, 45 Elda Drive, San Rafael, CA 94903-3723, U.S.A.
REVISED ASCII SCHEMATIC OF McGREEVY BBB-4 ELF/VLF RECEIVER w/LINE #'S:
(Sorry about the ascii text "graphics" -- I'm not too good
at doing schematics using text characters, but I wanted this to
be fully compatible with the text-only nature of USENET, etc.
NOTE: I've added line numbers to aid with "fixing" any scrambled lines:
These numbers are at the BEGINNING of each line in schematic (01 to 72).
--------------------------------------------------------------------------
01) __________ o +9 Volts
02) \ | / |
03) \ | / ___________________|_____________\ To Audio
04) \ | / C9 + | |0.1uF | / amp. 9 v
05) \ |/ 100uF __|__ __|__ C10 | rail.
06) \/ _____ _____ |
07) | | | \
08) 1 to | |__________| / 4.7K
09) 3 mtr.| __|__ \ R4
10) whip | R1 C1 / / / 2N5484 /
11) ant. | 1 Meg. 0.1uF Q1 D |_______||____\ To filter &
12) | G |_____| || / A.F. AMP.
13) |---/\/\/\---||---|-----|-------| 0.1 uF
14) | | |-----| C3
15) C2 _|_ \ S |
16) 47pF ___ / R2 /
17) | \ 10 Meg. \
18) | / / 1K
19) | | \ R3
20) |-----| /
21) __|__ __|__
22) / / / / / /
23)
24)-------------------------------------------------------------------------
25) AUDIO FILTER
26) * (^^^ = coil windings)
27) From FET drain coupling L1 (xfmr pri.) or 180-200 mH choke
28) cap. ==============
29) \_____ _________|^^^^^^|^^^^^^ To input of
30) / | |_______________| |____\ bi-polar
31) | | | | / audio amp.
32) | .0047 uF | 0.1 uF
33) __|__ C4 .0047 uF | C6
34) _____ C5 __|__
35) | _____
36) | |
37) | |
38) __|__ __|__
39) / / / / / /
40)
41)
42) * L1 is a 1 KCT pri. to 8 ohm sec. audio xfmr. using one end of primary
43) winding and the center-tap as a series inductor equalling approx 160 mH.
44)
45)-------------------------------------------------------------------------
46) MIC. LEVEL NPN AUDIO AMPLIFIER
47) (+9 volt rail)
48) \__________________________________
49) / | |
50) | 10 K /
51) 33 K \ R7 \
52) R5 / / MIC. LEVEL
53) \ C ____|______| |_______\ OUTPUT
54) From audio / / | | / To tape rec. or
55) filter | B | / 0.1 uF speaker amp.
56) \________________|_________|/ C8
57) / | |\__
58) | Q2 | \/ E
59) | 2N3904 \______
60) | NPN | |
61) | Bipolar + | |
62) | Transistor __|__ \
63) \ 1uF _____ / R8
64) 4.7K / C7 | \ 1.5K
65) R6 \ | /
66) / |_____|
67) | |
68) __|__ __|__
69) / / / / / /
70)
71)
72)-------------------------------------------------------------------------
The "BBB-4" is a broadband 0.2 to 11 kHz V.L.F. receiver with a
passband peak at approximately 2 kHz, and is designed to receive
naturally-occurring V.L.F. phenomena (such as "whistlers") that occur as
electromagnetic (radio) waves at audio-frequencies. This receiver was
designed to be hand-held, and its output patched to a microphone-level input
such as a tape-recorder or speaker-amplifier (such as the one available at
Radio Shack ("Mini Audio Amplifier/Speaker" cat. # 277-1008).
Dissatisfied with more complicated and cumbersome multi-turn loop receiver
schemes, I opted to design a whistler receiver which was simple to build and
use, but was as sensitive and low-noise as possible while being highly-
immune to broadcast station overload.
The BBB-4 V.L.F. receiver circuit ("BBB-4" standing for a fourth
version of my "Bare-Bones-Basic" designs) is remarkably sensitive and
works very well with short whip antennas between 30-60 inches in length,
since it operates on the same principle as high-impedance "active antennas"
designed for other frequency ranges (such as long, medium or shortwaves).
The BBB-4, due to its F.E.T. "front-end" being a high-performance J-FET,
has an input impedance of about 10 megohms, which is why the short whip
antenna--more correctly called an "electrical-field probe"--works fantastically
for being such a tiny fraction of the received-frequencies' wavelengths in
size (the ultimate isotropic antenna).
R1 and C2 act as a roll-off to frequencies above about 20 kHz,
efficiently eliminating potential receiver overload/intermod from Loran-C
(100 kHz), strong AM-BCB signals or SWBC signals, and frequencies up
into the VHF ranges. R2 sets the gate impedance for the J-FET. R4 and R3
set the optimum bias on the FET for maximum dynamic range and minimum
susceptibility to overload and intermod. C3 and C6 slightly helps roll-off
low-frequencies such as powerline "hum." The "pi-filter" consisting of C4,
L1 and C5 roll-off frequencies beginning at about 7 kHz, so there are not
excessive levels of 10.2 - 13.6 kHz "Omega" signals or higher frequency
signals, which can create problems with the recording system connected to
the output of the receiver. R5 to R8 , Q2 and C7 form a fairly low-noise
Class-A audio amplifier which boosts the output from Q1 to a level plenty for
all microphone-level recorder inputs and even some more "sensitive" line-
level inputs. Bypassing R3 (1K) with a 2.2 uF cap will boost FET gain
somewhat, esp. the higher frequencies--depending on your location
and listening conditions, this may or may not be desireable.
The circuit can be built on perfboard such as IC-LSI boards or even
wired point-to-point, as layout is not very critical. However, the parts'
values ARE critical for optimum passband shape and sensitivity. L1, the
inductor, can either be a 160-200 mH choke or the Radio-Shack 1K to 8 ohm audio
transformer available at Radio-Shack (cat. # 273-1380). Use the black and
green or black and blue wires (the center-tap and one end of the primary
winding). The audio transformer was used since it is easily available at
Radio Shack stores. In fact, ALL the parts with the exception of the 2N5484
FET are available at Radio Shack. Very good performance (but slightly
reduced gain) can also be had if a 2N3819 J-FET, available at Radio Shack,
is used. If so, R3 must be 220 ohm and R4 must be 1K, because the 2N3819
needs different biasing than the 2N5484. Also, if you use the Radio Shack
2N3819 FET, you might wish to reduce C4 and C5 to .033 mF, since there
will be less high audio-frequency output from the 2N3819. Keep C4 and C5
.047 mF if you live in Hawaii or within 300 miles of La Moure, ND (south-
eastern North Dakota) due to the Omega-navigation transmitters (frequency
stepping from 10.2 to 13.6 kHz) being located there. Capacitors C4 and C5
work with L1 to reduce Omega to tolerable levels. Solder the J-FET into the
circuit LAST, and take measures to protect the FET from static electricity.
The total cost for parts (not including an enclosure) for the BBB-4 are in the
neighborhood of $15-20 U.S. A rugged telescoping-whip antenna is the GROVE
ENTERPRISES "ANT-8" 7-46-inch telescoping whip with a BNC
connector. This is available for $16.95 from Grove Enterprises, P.O. Box 98,
Brasstown, NC 28902-0098, U.S.A. (Order Line 1 (800) 438-8155. They
send out a free catalog.
Another telescoping whip antenna of like design is
available from C. CRANE RADIO CO. in Fortuna, CA in Fortuna,
California (800) 522-TUNE (522-8863). E-field-probe receivers of this type
need to be operated at locations away from trees, buildings, or other
obstacles by about 100 feet/30 meters. This is because received
signal levels (due to E-field attenuation) will be poor if the receiver is
operated too near (or under) such obstructions.
The greatest nemesis to monitoring and recording naturally occurring
VLF phenomena are electric a.c. powerlines, which emit annoying hum at
50/60 Hertz and also harmonics beyond 3 kHz. The only cure for this "hum"
problem it to locate monitoring sites well away from a.c. powerlines.
Locations at least 1/2 mile/1 km or so away from a.c. powerlines will begin
to be acceptable, though the farther you can get from powerlines, the better.
Hilly or mountainous terrain (with open areas free of trees) offer larger areas
away from powerlines, though large fields and meadows where the
powerlines are shielded by trees, etc. may be surprisingly hum-free. Remote
locations such as deep into desert and wilderness regions offer the most
rewarding locations, both aesthetically and electrically, to listen, and you may
be able to get over 10 miles from the nearest powerline. If so, you can make
the receiver's antenna several meters in length (keeping it vertical) for
maximum sensitivity. Longer vertical antennas or horizontal wires may
either overload the receiver, or in the case of long/low wires, will create a
mismatch which will actually reduce output. Experiment here.
NOTE: A 100 mH choke across C5 (th secone .47 cap in the audio filter
will greatly reduce the below-1 kHz frequencies, including pesky power-
line hum. This may enable you to listen far closer to AC power-lines
including even some backyard locations!
Grounding is non-critical. High-impedance FET receivers of this type
need only minimal grounding to work well_even just the body of the listener
holding the metal enclosure of the receiver will be adequate in most cases. If
recording, it is best to stick a 8-10 inch ground rod into the soil to reduce the
possibility of feedback with some tape recorders. Also, a small ground-rod
(8-10 inches long) will cut noise from body or foot movements (due to
capacitive interaction with the ground). If you ground the receiver to objects
such as fences, beware that certain grounds may couple a.c. powerline noise
to the receiver, which is why I recommend a simple Earth ground.
Better quality tape recorders, with adjustable input level controls, are
desirable, as "cheapie" portable recorders with auto-level control will often
have annoying variations in record level due to lightning-sferics. And, these
cheap recorders also put noise of their own onto the tape. A shielded 600 ohm
patch-cord will suffice between the output of the BBB-4 and microphone
input of a tape recorder.
The most common naturally occurring V.L.F. emissions to be heard
are the myriad "crackling and popping" sounds of lightning-stroke
electromagnetic impulses from lightning storms within a couple thousand-
mile radius of the listener. Since there are nearly 100 lightning storms in
progress anywhere on the Earth at any given time, and that millions of
lightning strokes happen daily, there is never a moment when these lightning
"sferics" will not be heard. However, the density and strength of lightning
sferics can vary day-to-day and hour-to-hour. Mid-winter offers the lowest
density of sferics, and summer evenings can be full of a dense barrage of
strong sferics.
The other most common (and most awesome) sounds are "whistlers"_eerie
descending tones caused when the lightning electromagnetic energy gets
"ducted" along Earth's magnetic lines-of-force (magnetosphere) to the
opposite polar hemisphere, then gets rebounded back to the vicinity of the
originating lightning stroke impulse. However, there doesn't have to be
lightning within sight or even a few hundred miles of your listening
location_lightning from storms up to thousands of miles away, particularly if
more to the north of your location, can generate large whistlers which are
heard continent-wide. On the other hand, it's quite spectacular to watch
distant lightning storms generate whistlers in the receiver's output_you hear
the huge "crack" of the lightning impulse sferic, then, if the conditions to
support whistlers are occurring, a whistler may follow from 1 to 2 seconds
after the lightning stroke.
Optimum times to listen for natural V.L.F. phenomena, such as
whistlers, are between sunset and sunrise, with the midnight to sunrise period
generally being the best. Statistically, the greatest activity to be heard is
around dawn and sunrise (4-7 a.m. local time)_sferics tend to be fairly low as
compared to the sunset period.
Dawn Chorus can occur during magnetic-
storms, and will peak anywhere from an hour before sunrise to 2 hours past
sunrise. Whistlers can occur at anytime, but the period of minimum
frequency is midday. Sometimes, activity can also occur just after sunset,
but sferics will be fiercer. Lightning sferics will be most fierce during
summer afternoons and minimum (generally) an hour or so after sunrise until
thunderstorm activity picks up later on. Winter can present delightfully low
lightning sferics_other activity will be more "in the clear."
Tweeks, the "ringing/pinging" sounds of sferics caused by the Earth-
surface/ionosphere "waveguide," will be best from an hour after sunset to 2-3
a.m. local time, gradually tapering off toward sunrise. Their number and
intensity of "pinginess" can vary from night to night_some nights they can
sound rather "pale," but other nights they can ring in a variety of beautiful
mixtures and pitches. Whistlers, which may or may not be heard on some
days or even weeks, can range in sound from quite pure notes to very diffuse
"breathy" sounds. They can swoop in frequency from very high to low, or
abruptly cut-off as they descend in pitch.
Don't be discouraged if you listen for several hours, or several sessions on
different days, without hearing whistlers or other natural radio phenomena.
When you DO hear them, it will make up for the "dry" times, as there is
nothing like "live" listening!
Listeners located north between 40-55 degrees north or south latitude
are in the optimum latitudes for monitoring natural V.L.F. phenomena. If
you can see visible Aurora (Northern/Southern Lights) from your location,
you are at a great location for natural V.L.F phenomena monitoring!
Latitudes between 20-30 degrees north and south will hear less, but at times,
still loud phenomena. I've heard whistlers just fine in Hawaii_presumably
those whistlers were louder farther north, but still, they were heard!
DO NOT operate this receiver (or any other) when nearby lightning
threatens! Take appropriate lightning precautions when lightning is
occurring nearby (within 5-10 miles). Nearby lightning will cause
excessively loud sferics in the receiver's output, and whistlers will not be
louder just because lightning is close-by. Reserve listening for fair weather
periods_most often, the best and loudest natural V.L.F. phenomena will
happen during clear weather, since lightning can be quite distant, as
mentioned above, and still spawn loud whistlers.
If you would like to purchase a ready-made receiver which is
fashioned like a "Walkman-style" whistler receiver, e-mail me for
details. I don't want to "advertise" here.
The Longwave Club of America also has other designs of ELF/VLF "whistler"
receivers, and has a BBS run by member John Davis. The LWCA BBS is at
(706) 672-0360 with speeds up to 9600 (8,N,1). Download the
ALLFILES.TXT or ALLFILES.ZIP for listing of files avail on this BBS.
A WWW URL of natural radio WAV files (most 8 bit/11 kHz sampling
compatible with Windows "speaker.drv" as well as 8-bit sound cards, plus a
few 16-bit files for 16-bit sound cards are available for downloading at:
http://www-pw.physics.uiowa.edu/mcgreevy/
Special thanks to Larry Granroth a the U. of Iowa for doing this for me!
Coordinated monitoring of naturally occurring V.L.F. phenomena
among individuals and groups has a strong potential to uncover new and
previously unknown characteristics of these phenomena, particularly if those
monitoring simultaneously are located hundreds and thousands of miles
apart. Research and understanding of V.L.F. phenomena has been hindered
by a lack of listeners, which is something a few research groups, both
amateur and professional, are attempting to alleviate.
I hope you enjoy this rcvr. and are interested in monitoring and
studying naturally occurring VLF radio phenomena for yourself. It is quite
fascinating, especially when one ponders the fact that Earth's natural radio
emissions have been "sounding-off" way before we Humans came into
existence and started making radio waves of our own! Happy Listening!
Stephen P. McGreevy
Originally released November 1993, updated November 1995
Additional Tips:
1) A 100-200 mH inductor connected across C5 the will act as a
high-pass filter, nicely attenuating 60-360 Hz powerline emissions (hum).
2) If you want less gain from the Q2 stage (and slightly lower noise),
reduce R8
to 4.7K.
3) Listen to WWV-shortwave (2.5, 5, 10, 15, 20 MHz) for geo-
magnetic indices at 18 min. past each hour (WWVH-Hawaii at :45). A K-
index at or above 3 indicates enhanced conditions for natural phenomena,
especially chorus.
73,
Stephen P. McGreevy, N6NKS
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