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 
                        following formats:

                          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


  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, 

        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 
                        as PARITY14.
        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 
                        600 bd


  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 
  use above!

  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