The Russian Anti Aircraft Defense PVO (Protivo Vozdushnoy Oborony) operates a surveillance, early warning, height finding and fire control network for Russia, Belarus and Kazakhstan. Since the 1998 amalgamation of PVO and Russian Air Force VVS the common command post is in Zarya, near Balashika, some 20 km NE of Moscow centre.

Most of the aircraft tracking system nowaday is satellite based. But we still can hear radar stations, transmitting regularly strings of figures in Morse code.
Radio monitors since many years listen to these transmissions. Although it is not a Number Station it is still logged as network M21 (ENIGMA2000 designation). In the meantime we know more and 2002 Ary Boender wrote an excellent profile about M21, which you can find here: Downloads.

M21 transmissions easely can be recognised, because of
- the preamble "="
- the time strings on the minute, if there are no messages
- the blind traffic (no callsigns)
- their reasonable low speed.

It seems that M21 picks frequencies out of a pool, although some are replaced by others. It is worth to try here:
2818.5, 5873, 4391, 6823.5, 9220, 3314, 3322, 4951.5, 4631, 4145, 5918.5, 7994 kHz and many others.

Other radar tracking networks

There are however other stations around, which seem to transmit tracking results in Morse code as well, but do not belong to M21. Messages start without preamble and mostly contain 12...13 figures, the last 2 indicating time in minutes, but there are figure-groups of any length. Sometimes a // frequency has been observed or callsigns are repeated a few times. Transmission speed is quite high. It is not clear, if one or several networks are involved and it is not an easy task to sort that out.

Looking for things in common you'll find that some messages are preceded by the priority code "wzd" and are repeated after "abv". These trigrams I first heard around 1970, when we monitored the Air Defense of the GDR (German Democratic Republic),
which was closely linked to the Sovjet Forces in GDR. And I noticed, that the same stations with the trigrams quite often used the same callsigns for a long time.

Could it be, there are still remnants of that system? Does Russia still use parts of that huge network, which was used by the Warsaw Pact?
It is well possible and when 2008, after many years, voice reports re-appeared, reading very fast strings of figures in Russian language, I am quite sure: they're still around in one way or another.

I thought it might be a good idea to look back onto the original tracking reports, used by the Air Defense Forces of the GDR. They had this format:

00 01 07 37999 9 1 100 1303

00	Signal: Specifies the status, e.g. target registered, target lost, target destroyed, etc
01	Tracking station: Identification number.
07	Track number.
37999	Coordinates.
9	Target identification: Friendly, hostile, scheduled airliner, etc.
1	Number of aircrafts involved. (Target ID and number of aircrafts = index)
100	Height of target.
1303	Time: local or UTC?

Subsequent tracks of the same target were sent in an abbreviated format of 16 figures. I did not find, when a message was urgent (wzd) or how the coordinates were calculated.

It is obvious, that the whole organisation of the GDR Air Defense for the Display of the Airspace (Darstellung der Luftlage) was enormous. The system in use was MIDA, no details are available. The best place for additional informations is the Website of the "Funktechnischen Truppen der NVA": http://www.nva-futt.de .

Years ago E2k assigned intercepts of these stations to M41 and it might be ok to still use that name. It is obvious, which Russian PVO tracking results are M21 (start with "=", use time strings and "?"), but what PVO stations should I log as M41?
To make a start, M41 messages should
- use the "wzd" and "abv" trigrams or contain callsigns and
- end with time in minutes.
Voice transmissions I do include here as well, as I don't understand them ;-)


This implies traffic sometimes must be observed for hours - can be frustrating, as M41 stations are not easy to find.

This is a selection of M41 frequencies and callsigns until 12.2008:

3301 // 4959 PSNN, YM8G, F6CU, VQK4, WLSB, 4K7U, QJ9M, BTHD
4444.5 EQM2
4484.5 GWKT, NOFJ
5210.5 YM8G
5372 PSNN
5733.5 PMZW
10158 ON8A
13482 GD5S

2820 USB Voice OM
3835 USB Voice YL

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