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G0FTD > JAMMER 22.03.05 08:33l 136 Lines 6509 Bytes #999 (0) @ WW
BID : 319905G0FTD
Read: DK5RAS GUEST
Subj: Cold War Jammers Part 2/4
Path: DB0FHN<DB0FOR<DB0SIF<DB0EA<DB0ACC<DB0GOS<ON0AR<ON0AR<ON0AR<F6KMO<
7M3TJZ<HG8LXL<CX2SA<GB7CIP<GB7SXE
Sent: 050321/1651Z @:GB7SXE.#38.GBR.EU #:25599 [Hastings] FBB7.00i $:319905G0FT
From: G0FTD@GB7SXE.#38.GBR.EU
To : JAMMER@WW
And now, a little bit about the objekts.
These were nothing more than broadcasting stations which contained
various transmitters. For instance, broadcasting station nr. 65 consisted
of:
shortwave transmitters 1kW 10pcs
US military 1-1 transmitter SCR 1pc
medium wave transmitter Uragan 10kW 1pc (water cooled)
long wave transmitter Storm 3kW 1pc (air cooled)
and 2 smaller k-1 transmitters which were rarely ever used
Objekt nr. 65 was headed by a Russian woman named Gorelova, who had
graduated from the Leningrad Communications Institute.
Objekt nr. 602 consisted of 10 4kW shortwave transmitters. This was also
headed by a Russian woman.
The Tartu and Pärnu objekts consisted mostly of US military SCR type
shortwave transmitters.
The objekts and transmitters were numbered in sequence. The numeration of
the objekts was as follows:
the older type, equipped with 1-1 transmitters:
nr. 65 - in Tallinn, Sitsi Hill
nr. 66 - probably in Tartu
nr. 67 - probably in Pärnu
the rest of the objekts of this type were located outside of Estonia.
The newer type, equipped with more powerful transmitters:
nr. 602 - in Tallinn, on Luha Street. This was the only broadcasting
station of its type in Estonia.
Numeration of transmitters: every transmitter had its own number. The
numbers were assigned in sequence, within each city, irrespective of
how many objekts there were in that city. Therefore, transmitters nr.
1-10 were located at objekt nr. 602, transmitters nr. 11-26 at objekt
nr. 65. Nr. 1-10 were, for instance, 1-1 4kW transmitters, nr. 11, on
the other hand, a Uragan transmitter.
The radio bureaus (Tartu and Pärnu had their own radio bureaus)
communicated with the objekts via special direct telephone lines.
The Noise Generator.
The noise with which we jammed the incoming broadcasts was produced by
a special generator. This was known as the GMD - generator meshajushtshego
deitsvija, in direct translation, the interference activity generator.
Each objekt had a GMD, and each radio bureau had one as a back-up. After
every minute of producing interference noise, each generator would also
transmit its call sign. For instance, objekt 65's call sign was the Morse
code letter for Y, objekt 602's, the Morse letter for V.
A GMD unit actually consists of four separate generators, each one with
a twin triode 6N7 (see diagram).
G1 gives the frequency 135Hz
G2 gives the frequency 320Hz
G3 gives the frequency 3Hz
G4 gives the frequency 5Hz
All of them are multivibrators, therefore, impulse current generators.
G1 and G3 are the basic generators, while G2 and G4 are the sub-
generators, which modulate the frequency of the basic generators.
G2 modulates G1's frequency by +-3Hz, and G4 modulates G3's frequency
by +-5Hz. The noise produced by G1 and G3 are blended together to create
the constant static and blaring with which the radio broadcasts were
jammed, and which the radio listener finally heard. These Russian noise
generators were actually quite cleverly made. Although all LW, MW, and
SW broadcasts were always amplitude modulated (AM), amplitude modulation
was not used for jamming, but rather frequency modulation (FM). And this,
on such a narrow strip as is needed in a band for 1 station, that is,
9-10kHz. If the transmission bearing wave is viewed with an oscillograph,
the modulation cannot even be observed, as if it didn't exist.
The noise generator was regarded as the most secret device at the objekt.
Outwardly, it didn't differ in any way from a common amplifier. On photo
nr. 3, a generator (on the bottom) can be seen on a stand together with
common amplifiers.
The noise generator, or jammer, was the last device to be explained to a
new employee at an objekt. Any other Estonian Radio Centre employee who
came there and happened to ask questions about the device, was told that
it was just one of the many amplifiers in the broadcasting station.
As a matter of fact, I had an experience like that when I was still going
to Technical School and was doing my internship at Laitse radio
broadcasting station. For some reason, they had a GMD there at the time.
I stumbled upon it, and not knowing what it was, of course made inquiries.
The response was, that this was a modulation amplifier.
Frequencies.
We were able to jam broadcasts in the long- and medium wave diapason,
and shortwave broadcasts on bands 13, 16, 19, 25, 31, 41, 49m. I even
remember some of the frequencies. In long wave, we worked on frequency
173kHz, and in medium wave, mostly on frequency 1195kHz - that was
Munich.
Another episode illustrating the extreme secrecy surrounding the work.
During work, we had to make notes. We had to jot down the frequencies
that the radio bureau gave us, so that we could adjust the transmitters
accordingly. After a 15 minute broadcast, we no longer needed these
notes. But we weren't allowed to write down the frequencies on a regular
piece of paper, since those are thrown into the garbage, and could end
up in the hands of enemy spies. Can you imagine - an American spy would
be able to find out Voice of America's broadcasting frequencies!
For making notes, we were given special notebooks with numbered pages,
which were bound together with string, the ends of which were sealed
together. When the notebook was filled, it had to be given to the
superior, upon which it was destroyed, or even placed in the archives.
The jamming itself was done in the following fashion. The radio bureau
operator informed us what frequencies to expect at what times. At the
same time, she would be monitoring the broadcasts. When we were jamming
Voice of America, the operator would maintain contact with us via the
special telephone lines. Beside every transmitter, there was a telephone,
so that the technician and operator could be in constant contact.
Together they would try to get the jammer onto the exact frequency mode.
We weren't permitted to turn off the jammer until the operator said so.
Since our transmitters at Sitsi were not of especially high quality,
they would tend to wander off the frequency, and the Voice of America
broadcast would come in clearly. But since the radio bureau was
constantly monitoring the incoming broadcasts they would inform us of
these shifts, so that we would have to make adjustments to the
transmitters. Sometimes, friends who were trying to listen to VOA would
phone us and ask us to turn the jammer off on some particular frequency.
(Continued in part 3)...
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