INTERCEPTING SPACECRAFT RADIO SIGNALS
FROM THE SECRETIVE SOVIET SPACE PROGRAM
DURING THE COLD WAR ERA

SATELLITE SIGNALS RECEIVED FROM MY HOME IN SHERWOOD, ARKANSAS USA
AARON GEORGE BAILEY - WA5HRC
HOMEBREW RECEIVER CONFIGURATION FOR MONITORING SALYUT-6 / SOYUZ IN 1978

In late 1977, through listening to the "AMSAT  HAM RADIO NET", I learned about the frequencies of
Salyut-6, Russia's newest space station.(^also see below- Richard Flagg and Mark Severance)  Back in
those days you couldn't go out and buy
a fancy digital scanner radio.  I had to make do with the radio gear
that I had available.  But actually, the challenge of putting together a listening station, the planning, and
the building and modification of equipment was a big part of the fun.  After some thought, I decided on
how to patch together various pieces of equipment into a workable configuration in order to hear voice
signals from Salyut-6   Firstly, and perhaps most important of all as any Radio Amateur knows, was a good
antenna.  I chose to build a Quagi beam with a boom made of PVC pipe and the elements made of heavy
wire.  The Quagi had receive gain and was somewhat directional and proved itself to be a splendid
performer for my needs.
(+)  I usually kept it pointed in a northeasterly direction (or NE by E) since the
Salyut-6 radio sessions with the tracking ship would be low on the Eastern horizon relative to my listening
station.  All of my other gear was hand built kits, mostly
Heathkits, with the exception of the Vanguard
antenna preamp which was factory built.  The
121.750MHz Salyut-6 signal was broadband FM or (Wide Band
Frequency Modulation- WBFM) and this presented a problem because my Aircraft Radio could only detect
AM-(Amplitude Modulation).  While it is possible to tune an AM radio slightly to one side of a FM signal and
produce understandable audio.  Called Slope Detection, this tuning method works but at the cost of
receive sensitivity.  I was tuning for weak signals so I needed to modify my radio setup for the highest
sensitivity and still be able to detect the WBFM signal.  Back in those days electronic circuits were less
compact and fun to tinker with.  By contrast, todays radio circuits are microscopic and you need the steady
hands of a brain surgeon and big magnifying glass to work on them.  So with high hopes I made the
necessary circuit changes.  And then, as any electronics experimenter knows, that climatic moment
arrived when the circuit is powered up for the first time, and the big question is, "Will it work, and fail the
smoke test, or will it just smoke"?   This was a common fear back in the old days when you were working
with high voltage tube circuits.  Well, actually, this time I was working with
low power transistor circuits
and normally they don't smoke.  But a wiring error in a high powered
vacuum tube circuit from that era was
capable of fireworks, like a pop and flash from an electrolytic capacitor.  And yes, these type of surprises
were also accompanied by lots of foul smelling smoke, especially from overloaded carbon resisters.  This
time fate was kind and the circuits survived my operation.  In the final form, my Aircraft Radio
down-converted the incoming space signal to 10.7MHz.  This "IF" signal was then fed into the 10.7MHz "IF"
strip of a WBFM broadcast band radio.  The tuner on this FM set was disabled to reduce the sum of noise
and the two radio circuits were coupled together using some coax and a gimmick capacitor.  A "gimmick"
is simply two insulated wires twisted together a few turns and tuned for best operation by experimentally
adding or removing turns.  Much to my amazement, this hookup scheme worked well and for the first time I
was able to receive good quality VHF voice signals from the secretive Soviet space program.  

In those days the Soviets kept a
tracking ship(s) in the Western Atlantic or sometimes in the Gulf of
Mexico.  Unlike America's NASA, the Soviets didn't have a worldwide network of ground based tracking
stations but instead they relied on tracking ships.  Western intelligence analysts studied the locations of
these ships, and if in port, assumed that nothing was up.  But in the early years, when they went to sea and
where they were stationed at sea was a good indicator that a Soviet space shot was eminent.  Beginning
with Salyut-6 the tracking ships did long duty on station acting as a communications relay, via satellite, that
linked Salyut-6 radio traffic back and forth to Mission Control near Moscow.  In fact,
the signal from
Salyut-6 was of such good quality that I could hear the Mission Control voices in the background, coming
in over the speaker inside Salyut.  Sometimes North American aircraft could be heard coming in over the
speaker which indicates the signal being UPLINKED to Salyut must have been within the aviation band.  
The Salyut-6 cabin was noisy, you could hear fans and high pitched sounds like the hum from an inverter
and sometimes the crew would be singing, laughing or playing music in the background.  From my vantage
point the transmitter was turned on most of the time, called HOT MIC mode.  On occasions Salyut would
pass over with the transmitter on and not a word was heard, as if crew was  sleeping.   Mostly, Salyut-6
communications was operated Duplex as with the later Salyut-7 and Mir.  With a duplex radio setup both
stations have a separate receive and transmit frequency and this allows both parties to have a normal
uninterrupted conversation, like when talking on the telephone.  By contrast, most two way radio is
operated Simplex with only one transmit / receive frequency making both sides continually have to switch
back and forth between listening and talking.  On one occasion I heard a strange wobbling tone being
downlinked on the voice channel and I reasoned that it was a kind of telemetry. It wasn't till years later that
I learned it was an ECG when I accidentally came across the same sound in the Swedish web site,
"Sven's
Space Place."  In retrospect, the Russians were open with their communications.  Only several times
during all the missions did I hear them scramble their voice transmissions.  They used an analog
scrambling technique, called Voice Inversion, where basically a tone is mixed in with the voice, which
makes normally low frequency voice components, higher in frequency, and inversely, makes the high
frequency voice components, low sounding.  To de-scramble, the tone is applied again and inverts the
scrambled, Donald Duck sounding voice, back to more or less normal speech.  Years ago police
departments used this same scrambling technique which can be easily overcome and, to my way of
thinking, is a waste of time and effort.  I don't understand why the Russians would bother to use such a
simple scrambling method?

Acquisition Of Signal- (AOS) -  Listening for
Salyut-6 to come over the radio horizon, was neat.  Salyut-6 had
a powerful transmitter which most of the time was left "turned on constantly - HOT MIC mode."  
Anticipating a pass, I would sometimes open the squelch a little bit early and just listen to the receiver
noise and wait.  Soon Salyut-6 would make its presence known as the background noise, over a period of
several seconds, would
slowly fade away until the receiver was completely,,,, quiet, except for the low
level cabin sounds.  If Salyut-6 was coming out of the West, when just about over Arkansas,
the crew
would start putting out radio calls, waiting for the tracking ship to acquire a lock on their signal.  The orbit
of Salyut-6 was forever changing which would bring it over at different times of day.  The crews work
schedule was set to Moscow time, considering the time shift for my location, a lot of the radio sessions
were in the early morning hours local time.   During the Salyut-6 era I was filled with enthusiasm and I even
manned my radio at odd hours throughout the night.  Oftentimes I would rush outside to turn the Quagi
beam, zeroing in on the spacecraft for better reception.  Using a voice operated switch (VOX), with
adjustable hang time, allowed me to turn on/off a tape recorder and operate my receiving station in an
automatic mode when I was sleeping or away from home.   Experimenting with a later
VOX version, a Radio
Shack talking clock was wired to trip with the squelch and automatically time tag the voice recordings,
although with weak signals this repeated too often and proved to be annoying.

(^) Also, many thanks to Soviet space trackers Richard Flagg and Mark Severance for their help (phone
conversations) during this time.  And a special thanks to Mark for the information he mailed me.

(+)  An antenna switch enabled me to instantly select between the Quagi beam and a 121.75 Mhz dipole.  
Sometimes, I would use the dipole during the early part of the radio session as Salyut-6 was passing
nearest to my location.   Then, when I had Loss-Of-Signal- LOS with the dipole, I would switch to the Quagi
and instantly have a good quality signal for a while longer.  I performed this test a number of times and  
was always impressed how effective the Quagi beam was, especially when Salyut-6 was low on my
horizon.  This is proof that having good antennas is so important for any listening post.



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THE JOY OF BEING AN UNBRIDLED AMATEUR EXPERIMENTER / BUILDER
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Initial radio
setup before
placing it in a
specially
designed roll
around cabinet.