THE RUSSIAN VLF NAVAID SYSTEM,
ALPHA, RSDN-20
By Trond JACOBSEN, Halden (NORWAY)
I think nearly everyone
interested in the really low radio frequencies, at one time or
another, has heard the “ bee-boo” sound of the Russian
radio navigation system Alpha. Or more precisely RSDN-20, as
the official Russian acronym for the system is, meaning “ normal
long-range navigation system “ where D stands for
long-range. Alpha / RSDN-20 is a hyperbolic navaid, the
Russian equivalent to the now closed western OMEGA VLF navaid
system. Although the former Soviet, now CIS, Alpha / RSDN-20
VLF navigation system has operated in relative obscurity over
the past tree decades, there is little information to be found
on the web, but it has been studied by several individuals,
and it’s existence has been publicized at a number of
conferences during that period.
 |
The ALPHA / RSDN-20 radionavigation system is transmitting a 3.6 sec long repeating sequence consisting of six 400 ms long frequency combinations with a 200 ms spacing. The Alpha / RSDN-20 signal spectrogram above are made with GRAM 5.0 and received at my QTH at 59°8’12’’N 11°23’55’’E on the 14 th of May 2000 at 0656 UTC. |
Tree of the Alpha /
RSDN-20 stations are received, Krasnodar, Revda and
Novosibirsk. The far-east station at Khabarovsk and the
station at Seyda in Turkmenistan are out of range or QRT.
The original consept
for Alpha / RSDN-20 was born in 1957. In 1962 was the start
for the implementation of the navigational system and already
then was the signals received and monitored at Harvard for a
few days. “The quality of the signals was poor” and “the exact
frequencies varied like those from rather poor crystals “, one
of the monitoring crew recalls. In 1968 was the system
operational with 3 stations at Krasnodar, Novosibirsk and
Komsomolsk-na-Amur. The RSDN-20 transmitter at Novosibirsk was
( and still is ) the master station. These tree
original transmitters are sometimes called Sigma in
literature. The same year was the stations listed in the
International Frequency List with six frequencies; 11.905 kHz,
12.500 kHz, 12.649 kHz, 13.281 kHz, 14.881 kHz and 15.625 kHz.
The International Frequency List also reported 500 kW ofpower
to the antenna at each location and at each frequency.
When representatives from Racal Marine
Electronics ( formerly Decca Navigator Company ) was attending
a fishing exhibition in Leningrad 1968, they recall visiting a
Russian fishing wessel were they was shown a navaid receiver
intended for us in the Arctic waters north of the former
Soviet Union. The receiver was designated by the acronym
PIRS-1R and the navaid system was at that time officially
called RSVT-1. With the tree original
RSDN-20 transmitters located almost on a line from west to
east across the Russian continent, the system coverage was
obviously not intended for Soviet domestic use. One would
assume it was originally intended for submarine as well as
aviation use in Polar and North American regions and possibly
also for the southern Asia and Indian Ocean regions.
With the prior tree
station configuration of RSDN-20, if one station were off air,
the remaining two would be virtually useless for navigation
and the overall system availability is very limited. In August
1991 a Soviet delegation at the IOA, ( International Omega
Association ), meeting in Vancouver headed by general Anatoliy
G. Funtikov announced that two new Alpha / RSDN-20 transmitter
sites had been constructed, one on the Kola peninsula near
Murmansk in Russia and one near Chardzhou in Turkmenistan. The
Murmansk transmitter located near the village of Revda was
given an exlusive frequency F4, 12.090773 kHz. The same was
done in Turkmenistan with the new transmitter at the village
of Seyda ( Seidi in Russian ) near Chardzou. With two more
transmitter sites the navigational system would be more
reliable and also more adapted for civilian use within the
former Soviet union. With this inclusion oftwo new
transmitters followed also a new transmitter sequence. At the
same IOA 16 meeting was there also given information of a new
uniqe frequency, F3p, from the master station at Novosibirsk.
This new frequency was 1/7.2 Hz higher in frequency than the
nominal F3. This has also been the observed with the
transmission from Revda and reported but not observed with the
segment 4 transmission from Seyda in Turkmenistan.
The RSDN-20 transmission sequence
The basic signal epoch
consists of six pulse periods in 3.6 sec. Compared to the
longer sequence ( 10 sec ) that was used for the Omega navaid,
Alpha / RSDN-20 are
more suitable for faster moving vehicles, i.e. aeroplanes.
The phase of each pulse
does not start at the same value each 3.6 sec epoch but rather
repeats in an overall period of 7 x 3.6 = 25.2 sec.
The pulse durations are
400 msec with 200 msec between pulses. The pulses contain no
known modulated or otherwise information. When the system is
off air for maintenance or other reasons there are sometimes
periods with test transmissions with other phase and sequence
patters then the normal one.
OLD
RSDN-20 transmission sequence by frequency:
|
Segment nr.
station
Frequency kHz |
1
|
2
|
3
|
4
|
5
|
6
|
| F3 14.880952 kHz |
Novosibirsk
|
Novosibirsk
|
|
|
Krasnodar
|
Komsomolsk-na-Amur
|
| F2 12.648809 kHz |
Komsomolsk-na-Amur
|
Krasnodar
|
|
|
|
Novosibirsk
|
| F1 11.904761 kHz |
Krasnodar
|
Komsomolsk-na-Amur
|
Novosibirsk
|
Novosibirsk
|
Novosibirsk
|
|
 |
A different
Alpha / RSDN-20 transmitter sequence. This Alpha /
RSDN-20 transmission from Krasnodar was received at my
QTH on the 9.th of May 200 at 0656 UTC. It consists of
a different pulse length sequence then the original
one and also making use of a pulsed signal at the
15.625 kHz alternative frequency. Transmitter patters
like this are not uncommon in periods when the system
are off-air for maintenance.
|
There has been some
speculations that the Alpha / RSDN-20 system use these
sequences for special navigational purposes,
until that is confirmed, such speculations are most likely
based on misunderstanding of the basic principles of
hyperbolic navigation.
NEW
RSDN-20 transmission sequence by frequency
|
Segment nr.
station
Frequency kHz |
1
|
2
|
3
|
4
|
5
|
6
|
|
F3p 14.881091 kHz
|
|
|
|
Novosibirsk,
Revda, Seyda
|
|
|
|
F3 14.880952 kHz
|
Krasnodar
|
Khabarovsk
|
Novosibirsk
|
|
Seyda
|
Revda
|
|
F2 12.648809 kHz
|
Revda
|
Novosibirsk
|
Khabarovsk
|
Krasnodar
|
|
Seyda
|
|
F4 12.090773 kHz
|
|
Revda
|
|
|
|
|
|
F5 12.044270 kHz
|
|
|
Seyda
|
|
|
|
|
F1
11.904761 kHz
|
Novosibirsk
|
Seyda
|
Krasnodar
|
Khabarovsk
|
Revda
|
|
NEW RSDN-20 sequence by
transmitter site
|
|
1
|
2
|
3
|
4
|
5
|
6
|
|
Novosibirsk
|
F1
|
F2
|
F3
|
F3p
|
|
|
|
Krasnodar
|
F3
|
|
F1
|
F2
|
|
|
|
Khabarovsk
|
|
F3
|
F2
|
F1
|
|
|
|
Revda
|
F2
|
F4
|
|
F3p
|
F1
|
F3
|
|
Seyda
|
|
F1
|
F5
|
F3p
|
F3
|
F2
|
The mysteries that is shrouding the Alpha / RSDN-20 navaid system to most of the VLF amateur community is also valid for the location of the different transmitters in the system. The stations at Novosibirsk in the south-sentral Russia and Krasnodar at the north shore of the Black Sea are close to the two respective towns. The far-east station are north of the town of Khabarovsk, close to the village of
El’ban, and NOT at Komsomolsk-na-Amur.
The station at the Kola
peninsula are near the village of Revda, quite a distance from
the port of Murmansk. And finally there is the only station
outside the Russian border, outside the town of Chardzou, near
the village of Seyda ( the Russians spell it Seidi ) in
Turkmenistan. This Alpha / RSDN-20 transmitter is most likely
not active as the Russians have problems with it.
But there can be
changes of transmitter sites in the future and even today the
best way to be certain of the actual positions of the
transmitter sites are by Radio Direction Finding. This should
be the rule for most of the interesting
transmitters on the VLF band. Take a look at the RDF PROJECT.
Radio Direction Finding is fun, interesting and not at all
difficult, join in and see how this really should be done.
A.) NOVOSIBIRSK 55:45:22.0 N 84:26:52.4 E
B.) KRASNODAR
45:24:17.9 N 38:09:29.0 E
C.) KHABAROVSK
50:04:23.9 N 136:36:24.1 E
D.) REVDA
68:02:07.8 N 34:41:00.0 E
I.) SEYDA
39:28:16.0 N 62:43:07.3 E
|
|
 |
|
The
location of the Alpha / RSDN-20 transmitter at the
urban-type settlement El’ban, North of Khabarovsk (Far
East).
|
The
location of the Alpha / RSDN-20 transmitter at the
village of Revda (Kola Pennisula).
|
The RSDN-20 frequencies
I shall not delve into
the details of hyperbolic navigation, but the reason for the
mathematical relationship between the transmitter frequencies
are bound up in the navigational purpose. The determination of
the exact signal characteristics is an interesting
mathematical puzzle. For the mathematical minded of you this
is as easy as a piece of cake. There is another way to make
out the exlusive Revda F4 frequency with another basenumber !
Can you find it ? The base harmonics that build up each signal
are seen to be separated by 1 /( 3.6 sec ) or 0.27777….. Hz,
but are not integer multiples of 0.27777…..Hz. Are there
exceptions to this rule ? The operational RSDN-20 system
frequencies are mathematical related to a base frequency of
744 1/21 Hz.
F0 744 1/21
Hz = 1MHz / 1344
F1 11904.76190
Hz = 16 x F0
F2 12648.80952
Hz = 17 x F0
F3 14880.95238
Hz = 20 x F0
F3p 14881.09127
Hz = F3 + (5/36)
F4 12090.77381
Hz = (260/16) x F0
F5 12044.27083
Hz = (259/16) x F0
There is also a set of
very rarely used
alternate frequencies wich are multiples of 781.25 Hz
F6 12500.00000
Hz = 16 x 781.25 Hz
F7 13281.25000
Hz = 17 x 781.25 Hz
F8 15625.00000
Hz = 20 x 781.25 Hz
 |
Alpha secondary frequencies.
This is a very
exclusive capture of the Alpha / RSDN-20 secondary
frequencies. The signal was received at my QTH on the
2.nd of June 2000 at 0947 UTC. Seconds later Alpha
went QRT for unknown reasons. The station transmitting
is Revda on the Kola peninsula in north-western
Russia.
|
The four different
frequencies are the tree known secondary frequencies, 12.500
kHz, 13.281 kHz and 15.625 kHz together with a new, previously
unlisted, Fx on 12.700 kHz. Note the weak continuous
background signal at 15.625 kHz. This transmission is very often received at my QTH.
The transmission is unidentified and most likely not a regular
part of the Alpha / RSDN-20 system sequence.
Sudden phase shifts
at 2100 UTC – 0000 Moscow time
Every day at 2100 UTC
there are sudden phase shifts, thes occur simultaneously and
with the same phase-shift on all stations. There is also
another phase-shift with the phase of each individual pulse to
time the shift relative to 2100 UTC. Since there is not an
integer number of cycles of each carrier in a 24 hour day,
these phase-shifts appear to be there to reset to zero phase
at the beginning of each day.
These shifts are
360°/7=51.4° for F2, 2x360°/7=102.9° for F3 and
3x360°/7=154.3° for F1
Early Soviet RSVT-1 receiver
Not easy to find info
on this one, but the receiver PIRS-1R is discussed in detail
in a 1974 textbook intended for students in the Soviet
maritime academy. The receiver weighed 226.5 kg and consumed
1.3 kW ! In the receiver a synchronized commutation module
detected the first pulse of the master station and drove five
mechanical drum commutators with positions for each pulse in
the epoch. The frequency of a quartz crystal was automatically
tuned to the master station via a servo-driven variable
capacitor. The phase of the master at one of the common
navigation frequencies was measured and stored via a phase
discriminator and a motor-driven phase rotator during the
appropriate segment. Simirarly, the master phase at the
difference of the two navigation frequencies was stored during
another segment. Then during the other segments, the slave
phases at the common and difference frequencies were measured
and stored with identical hardware, wich also drove indicator
dials and counters. Phase propagation corrections and fixes
were accomplished manually.
The
future for Alpha / RSDN-20
No one knows ! For the
time being ( 07072000 ) are the system only partially
operating. But this is not uncommon, there have been very long
maintenance periods in the past. The future for this kind of
navigational system don’t look bright. Even though the
operational expenses are low ( for comparison : the eight
Omega station costed only a total of $ 12M / year ) some “evil
tongues” in the UK have been speculating in the closure of the
Alpha / RSDN-20 system because of unpaid electricity bills. !
There is also a lot more to be written on Alpha, but that will
be the issue of an update.
A large thank you to:
Benjamin B. Peterson and Lori A.
Constantino at U.S. Coast
Guard Academy for valuable information.
Väinö Lehtoranta in Finland, Manfred
Kerckhoff in Germany and
Dave Oxnard in Holland for valuable information and
great inspiration.
Renato Romero for great inspiration and the idea of the
Open Lab, Radio Below 22 kHz.
The former Soviet Union Military Community
for constructing Alpha / RSDN-20.
The WEB for being there.
If
you have information or questions regarding Alpha / RSDN-20
or related topics, feel free to mail to: Trond Jacobsen trond.jacobsen@halden.net