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
location of the far-east
Alpha / RSDN-20 station
|
Revda
on the Kola peninsula in Russia at the village of
El’ban north of Khabarovsk.
|
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