1-C. PACKET-like signals.
While packet signals are a non-continuous signal much like SITOR-A their
sound is totally different from the regular chirp, chirp sound of SITOR-A.
These signals do not have the regular cadance of SITOR-A but have more of
a long duration burst sound.
PACKET A system used in Amateur Radio and MARS stations,
typically 300 bd on SW. Data is arranged in packets of
up to 256 bytes of 8 bit ASCII data. Each packets con-
tains a 1 byte start flag, 3 byte address field, 1 byte
control field, 0-256 bytes of data, 2 byte CRC and
finally a 1 byte end flag. Packets are transmitted with
no fixed timing. See the latest specification published
by the American Radio Relay League (ARRL) for complete
details on this system. Also known as AX25.
G-TOR Golay Transmission over Radio. An amateur system
developed by the engineers at Kantronics, Inc. G-tor's
main advantage is speed - up to 4 times faster than
pactor. It also incorporates a data-interleaving system
that assists in minimizing the effects of atmospheric
noise and has the ability to fix garbled data. G-tor
tries to perform all transmissions at 300 bd but drops
to 200 bd if difficulties are encountered and finally
to 100 bd. All acknowledgments (ACK's and NAK's) are
sent at 100 bd.
CLOVER A system developed by Radio Amateurs and sounds like
a "canary" when transmitting. A signal consists of a
1s burst + a long 20s data transmission. Clovers key
characteristics are band-width effeciency with high
error-corrected data rates. Clover adapts to conditions
by constantly monitoring the received signal. Parameters
which can affect quality and reliability of the trans-
mission such as block data errors, phase dispersion,
frequency offset, and signal to noise ration are
monitored. Based on this monitoring, Clover determines
the best modulation scheme to use. Clover supports the
format baud rate
BPSM 4 pulse binary phase 125 baud
QPSM 4 pulse quad phase 250 baud
8PSM 4 pulse 8 phase 375 baud
16PSM 4 pulse 16 phase 375 baud
8P2A 4 pulse 8 phase 2 amplitude 500 baud
16P2A 4 pulse 16 phase 2 amplitude 500 baud
Total band width for all modes is a narrow 500 Hz.
ACARS on HF ACARS, generally a VHF based system used by airplanes
and ground stations for passing tech info has been
noted on HF as part of a feasibility study. HFDL
(High-Frequency Datalink) was being tested in N.A
on 13339 kHz using 1200 bd on at least 9 Delta 767's.
The system uses PSK modulation and uses an adaptive
bit rate to support 300bps to 1800bps. See Monitoring
Times 6/95 Plane Talk or Digital Review in WUN 10/95
(V1/10) for more info.
1-D. MULTI-TONE signals.
These signals are distinctive in how they sound. A rapid succesion of tones,
almost music-like in quality is their main feature. A sophisticated decoder
and a rock steady receiver is needed to process these signals.
PICCOLO British FCO invented multi-tone synchronous system.
Main user WAS the British Government but is probably
British Military and Australian stations. A 6 tone
system (MK6) using ITA2 operated at 50 or 75 baud. A
12 tone system (MK12) using ASCII/ITA5 operated at 110
baud. Both systems can still be found on the air.
COQUELET MK 1 is an asynchronus 13 tone ITA2 system used by
French (possibly abandoned), Belgian military/police
and Austrian stations similiar to Piccolo. MK 2 is
a synchronous 8 tone ITA2 system used by the Algerians.
Typical baud rates of 13.33 and 26.67.
CROWD36 Soviet Piccolo system using 32 tones based on British
Piccolo, CIS diplomatic services and French diplomatic
services are unconfirmed users. Typically found at 40
baud. Also known as CIS Piccolo or URS multitone.
MIL188 An 8 tone (?) MFSK system. Also known as NATO MIL188 or
MFSK188. NOTE: the only known sample of this system is
actually believed to be tt2300b so how this signal
really looks and sounds is unknown.
TT2300b An 8 tone MFSK system manufactured by Thrane & Thrane,
used by British government Air Agencies and the French
LINK 11 A US Military/NATO 40 DPSK synchronous system using 15
tones (1 doppler tone + 14 data + 1 sync tone), the
14 data tones are 4-PSK modulated and spaced every 110
hz. The sync tone is 2-PSK modulated. Typical rates of
1364 b/s or 2250 b/s. This is a ground wave only system
and is also known as "Alligator". Klingenfuss indicates
a baud rate 2400. See also MIL-STD-188-203-1A.
AIRCALL A Racal MFSK 7 tone system.
1-E. FAX-like signals.
These signals are used for transmitting pictures, mostly marine weather
maps over the airwaves and make a distinctive scratch-like sound. Press-FAX
can still be found but with less frequency as Press services continue to
move to satellite.
FAX Weather-FAX and less often Press-FAX
HELLSCHREIBER FAX-like mode used by Chinese Internal Press (still?)
now used infrequently by European amateurs on 80m and
1-F. SYNCHRONOUS BIT STREAM signals.
These signals are distinctive in sound in that they are continuous and
posess a trilling quality. The sound of an idling signal is slightly
different from a signal actively sending traffic. Many signals idle for
long periods of time and send very little traffic, i.e. ARQ-E, ARQ-E3, or
ARQ-M2. They can be found all over the shortwave spectrum. Other signals
have a short idling phase and move directly into traffic and then terminate,
i.e. POL-ARQ, SITOR-B, RUM-FEC or FEC-A.
ARQ-N A single channel duplex ARQ system used by Italian
Diplo services, typically using 72, 96, 144 or 192 bd.
ARQ-E A very common single channel duplex ARQ system used by
French Military Forces and the German Gov, typically
48, 64, 72, 86, 96, 144 or 192 bd. Also known as
ARQ-E3 Another very common single channel duplex ARQ system
used by French Military Forces, typically 48, 64, 72,
86, 96, 144 or 192 bd.
ARQ-M2 A multiplex (time division duplex) ARQ w/2 data
channels, typically using 87, 96 or 200 bd. Also known
as TDM, ARQ-28, TDM-2, TDM-242, TDM-342 or 96-TDM.
ARQ-M4 A multiplex (time division duplex) ARQ w/4 data
channels, typically using 87, 96, 192 or 200 bd. Not
found much any longer but has been used by Chinese,
Vietnamese and Spanish embassies. Also known as
ARQ-56, TDM-4, TDM-242, TDM-342 or 192-TDM.
POL-ARQ A single channel duplex ARQ system used by Polish
Diplo services, typically at 100 bd. Can be easily
confused with Sitor-B.
QAM An ARQ system used by the Chinese, unknown usual
bd rates. A sample of this signal is available on the
Klingenfuss CD (CD#2/Trk9) or Cassette (Trk37). This
is also a label for the modulation technique Quad
Phase Shift Keying with Amplitude Modulation (QAM).
RAC-ARQ A Racal simplex ARQ system used by British military
stations, typically at 150 or 267 bd. This system is
heavily encrypted and permuted to minimize any stat-
istical information and supports selective addressing,
variable length messages and an error correcting code
able to correct 7 errors in 127 bits. See Klingenfuss
Radioteletype Code Manual, 13th Ed for more details.
AUTOSPEC A FEC system used by British coastal stations to
communicate with North Sea oil rigs, typically 62.3,
68.5 or 102.7 bd. Also known as Autospec-bauer or
SPREAD A FEC system, used by Romanian diplo stations, using
the Bauer code used by Autospec, with characters spread
over a large time span, designed to reduce burst and
fading errors. Typically 68.5, 102.7 or 137 bd. Also
known as SPREAD-11, SPREAD-21 or SPREAD-51 depending
on data spread in effect.
CIS A single channel duplex system using 11, 14 or 27 bits.
CIS-11 is used by Russian meteorological stations,
CIS-14 is reported to be used by Russian PTT stations
on links to the former republics. Typical baud rates
are: CIS-11 - 50, 100, 150, 200 and 300 bd, CIS-14 -
42.1, 47.5, 48, 50, 70.5, 72, 83.3, 84.21, 94.11, 96,
100, 144, 200 and 288 bd, CIS-27 - 50 and 100 bd.
CIS-11 is also known as TORG-11. CIS-14 is also known
DUP-ARQ-2 A synchronous system reported by European monitors,
first listed in Klingenfuss 14th Ed. Utility Guide.
Very little information available but its speculated
that the Norwegian Diplo service is using this mode.
Baud rates of 125 and 250 have been reported.
SITOR-B A FEC system used by Marine Information services and
the Amateur Radio community, typically 100 bd. Also
known as FEC or AMTOR.
TORG-10 A Soviet ARQ system used to transmit Meteo data,
typically 100 bd
81-81 Russian/URS Military System mainly 81 bd, pseudo random,
one or two characters, 12 bits, always encrypted. Mainly
a 2 ch system but there is a 40.5bd signal that is a
1 ch variant. Most commonly found baud rates are 36.5,
40.5, 73 and 81.
FEC-A A system used by Turkish and German Press and German
Diplo services, typically 96, 144, 192 or 288 bd.
HNG-FEC A FEC system used by Hungarian Diplo services, typically
100.05 bd. See Klingenfuss RadioTeletype Code Manual
13th Edition for teleprinter alphabet used by this
RUM-FEC A FEC system used by Rumanian Diplo services, typically
164.48 or 218.3 bd. Signals can be encrypted, in the
clear or bit-masked (have been known to use 10, 15, 24
or 31). Had been referred to as SAU-FEC in the past or
SI-FEC A Siemens FEC system used by Austrian and Indonesian
Diplo services, typically 96, 192 or 200 bd. Also
known as FEC-S or FEC1000 Simplex.
IRA-ARQ An ARQ system used by the Bulgarian Diplo services,
typically 75, 100, 110, 150, 180, 200, 240, 300 or
1-G. ASYNCHRONOUS BIT STREAM signals.
These signals sound like the continuous bit stream signals but with a subtle
cadence difference to them. They are most often encountered sending traffic.
BAUDOT A common signal used by the Amateur community, many
military and government services, typically 50, 75 or
100 bd. Inversion is possible but not frequently
encountered on the data bits, giving 2^5 (32) possible
arrangements. Also known as RTTY or ITA2.
LINK 4 Military encrypted Baudot, typically 75 baud. Also
known as "Beaver".
ASCII A rarely found signal used by the amateur community
typically 110, or 300 bd. Also known as ITA5 or IRA.
1-H. MULTI-CHANNEL/BUZZSAW like signals.
These signals are obnoxious in the way they sound. They have a very harsh
buzz-like quality. Tough to decode because many signals can be transmitted
together and even interleaved. Signal Diversity is often used - defined as
all channels sending the same traffic but shifted in frequency and shifted
in time. The receiving equipment combines the channels into a single channel
if 'X' channels agree. Many times the channels are encrypted. A spectrum
analyzer can be a great help in identifying the signal arrangement.
VFT A general term used to define many kinds of multi-
channel signals used by British Military, Canadian
Military and US Military. Many configurations are
6028 6028 Series Diversity is a commonly found VFT system
using 16 channels of 50 bd or 75 bd baudot each with
170 Hz shift used by US and Canadian Military.
MULCAST A system used by the US Military composed of 16
channels each with an 85 Hz shift.
1-I. SSTV - Slow Scan TV.
A picture transmition mode developed and used by the Amateur community.
While these signals are FAX-like in function they do not possess the
scratching quality of the FAX signal. The sound of an SSTV signal is more
tonal in its composition, I do not believe that each mode can be
distinguished by ear.
1-J Phase Shift Keying systems
Nearly all of the systems that we have outlined above use Frequency Shift
Keying (FSK) of one, two or more tones. However, there are many signals to
be heard on HF which are Phase modulated (Phase Shift Keying or PSK) in
nature. At present, only the Hoka Code30 is capable of demodulating such
signals, and as such, this area of "listening" remains a somewhat uncharted
area, and none of the systems known about so far have names like the ones we
However, Hoka's Code 30 provides a tool-set that allows the user to determine
the characteristics of a PSK system with little more effort than an FSK-based
one. This at least allows us ordinary mortals to "fingerprint" certain types
of system. In a nutshell, here are the commonly encountered PSK-based
2-4MHz region: Navigational aids sending Differential Global
Positioning System (DGPS) information using 250bps 4-phase
(or Quarternary) PSK (QPSK). Try 2834.0, 2805.0, 3226.0kHz
3-13MHz region: Unknown users and system sending 1280bps
data using an 4-phase, Offset QPSK scheme. These stations are
recognisable in that they are all placed on .081 offsets from a
kilohertz or half kilohertz point. At least 20 channels are known
to be in almost constant use. Try 9058.081, 7663.581, 5752.081,
and 13369.081kHz amongst others.
5-20MHz region: Unknown user and system sending 600bps data using
2-phase, or Binary PSK. Try 10662.8kHz. 1200bps and 2400bps signals
of a similiar nature have been found in this region also.
Detailed info on Decoder modes & features PART C