Digi-Modes by Les 9H4LP


The Committee


Construction projects
A HADARS club member currently living in Gozo forwarded to me a comprehensive document produced by Les 9H4LP which listed all the available machine generated modes as well as information about available computer software and frequencies used.

I felt that Les's work deserved a wider readership and fortunately Les agreed to me including the information on the HADARS website. Les’s original Word document is available here but what follows is my conversion into a web page. Be warned - this is a big document!



Hellschreiber Modes
MFSK Modes
Image Modes
Advanced Digital Modes
Hardware & Software
Modes & Frequencies
Glossary & Software


Communication technologies that are specifically designed to improve "live" HF keyboard operation can now be achieved which previously only theory, too complex, or too costly to implement to be practical. Thanks to the generosity of radio amateurs with programming knowledge, and to the Internet, new and powerful communications tools are available to all hams.

The evolution and wide spread use of the Personal Computer that include a digital sound card for Digital Signal Processing and FFT software techniques, is allowing radio amateurs to use these tools to develop new modes of digital communication.

The distinguishing features of live HF digital operation today are the use of lower power, compact or indoor antennas and courteous operating techniques. Crowding on a single band like 20 metres is partly to blame for this issue. Fortunately, the new digital modes are designed to improve performance for a wide range of operating conditions.

The main advantages are:

  • High sensitivity (low power required < 40 Watts into a dipole)
  • Very robust communications (useful in poor conditions & QRM)
  • Narrow transmission bandwidths
  • Error correction codes using FFT techniques used
  • Greater immunity to TVI and EMC
  • Computers allow automatic operation and logging
  • Digital modes help with amateurs with hearing and speech disabilities, and poor hand coordination.

Most of the modes mentioned here have a complete section devoted to them. When reading the mode summaries, please note the baud rates and bandwidths used. This short paper only presents information and data, with plenty of references for further reading and operating. Armed with this data, I hope to encourage radio amateurs to learn, try to out and enjoy these new digital modes!

Back to top


SiTOR-B (Sea Teletype Over Radio) revamped to AmTOR (Amateur Teletype Over Radio), being the first amateur mode using Error Correction Codes. In the early 1990’s this revolutionised Radio TeleTYpe (RTTY).

AmTOR Summary:

Symbol Rate100 baud
Typing speed6.6 CPS (66 WPM)
ITU-R description400HF 1B
Modulation2-FSK (Frequency Shift Keying)
Average Power50% (ARQ) Amplitude Request Repeat
100% (FEC) Forward Error Correction
Protocol (Mode ASynchronous Connected ARQ CCIR 476-4
Protocol (Mode BSynchronous Unconnected ARQ CCIR 476-4
Character SetMoore 4:3

There are commercial selective-calling versions of Mode B, known as SelFEC and NavTEX marine broadcasts on MF are readily copied with AmTOR. More modern ARQ modes like Pactor are now replacing AmTOR.

Back to top


Clover is a PSK mode which provides a full duplex simulation. It is well suited for HF operation (especially under good conditions). The original modem was named CLOVER-I, the latest DSP based modem is named CLOVER-II.

Clovers key characteristics are band-width efficiency with high error-corrected data rates. Clover adapts to conditions by constantly monitoring the received signal. Based on this monitoring, Clover is an advanced communications mode, or rather, a family of modes, designed in the early 1990’s.

Clover Summary:

Symbol Rate31.25 baud
Typing speedapprox 3-50 CPS (30-500 WPM)
ITU-R description500HJ2DEN or 500HJBEN
Modulation8,4, 2-FSK (Frequency Shift Keying) or
2-ASK (Amplitude Shift Keying)
Average Power50%
ProtocolSynchronous Connected ARQ with FEC coding
ProtocolSynchronous Unconnected FEC coding
Character SetITA-5 ASCII (any 8-bit code)

16P4A16-PSK, 4-ASK750ARQ, FEC
2DPSM2-PSK diversity62.5FEC

Back to top

Hellschreiber Modes

This was developed in 1927, by Dr Robert Hell as Hellschrieber (‘Bright-Writer’). Reuters and other press agencies continued to use it throughout World War 11 until the 1960’s, when it was replaced by the Telex Service. China, Japan, Russia, Greece and Arabic speaking peoples with ideographic languages used variants of Hellschreiber until the mid 1990’s when they were finally replaced by FAX. It was first used for Amateur use in 1979. Today Feld-Hell is the most widely used mode.

Feld-Hell Summary:

Symbol Rate122.5 baud
Typing speed2.5 CPS (25 WPM) using original font
ITU-R description350HA1C or 350HJ2C
Modulation2-ASK (ON-OFF Keying, CW)
Average Power22%
ProtocolQuasi-Synchronous unconnected scanned image
Character SetUser selectable fonts

Multi-Tone-Hell Summary:

Symbol Rate0 - 20 baud
Typing speed2 - 3 CPS (20 - 30 WPM) font dependent
ITU-R description200HF1C
Bandwidth100 - 200Hz
ModulationMFSK (7, 9, 10, 12-FSK)
Average Power80% (concurrent) 50% (sequential
ProtocolNon-Synchronous unconnected scanned image
Character SetUser selectable fonts

PSK-Hell or FM-Hell Summary:

Symbol Rate105 or 245 baud
Typing speed2.5 CPS (25 WPM) font dependent
ITU-R description210H/490HJ2C or 210H/490HF2C
Bandwidth210 or 490Hz
Modulation2-PSK (DPSK)
Average Power80%
ProtocolNon-Synchronous unconnected scanned image
Character SetUser selectable fonts

Back to top

MFSK Modes

The first MFSK modes were used by governments and diplomatic services. Namely Piccolo 1957 developed by the British Foreign Office. Coquelet used by French, Belgian and Algerian military and diplomatic services. They were generally equipped with encryption units. The modern MFSK16 mode was developed in 1999, for MS Windows and sound card, using FFT techniques by Nino Porcino IZ8BLY, along with MFSK8, Throb and FSK441. These modes do not require special synchronous modulation, due to the built-in software FFT detectors.

MFSK16 Summary:

Symbol Rate15.625 baud
Typing speed4 CPS (40 WPM)
ITU-R description316HF1B
Bandwidth316 Hz
Modulation16-FSK (coherent phase)
Average Power100%
ProtocolSynchronous unconnected bit stream with FEC
Character SetExtended 8-bit X-ASCII translated to Varicode

MFSK8 Summary:

Symbol Rate7.8125 baud
Typing speed2 CPS (19 WPM)
ITU-R description316HF1B
Modulation32-MFSK (coherent phase)
Average Power100%
ProtocolSynchronous unconnected bit stream with FEC
Character SetExtended 8-bit X-ASCII translated to Varicode

Throb Summary:

Symbol Rate1, 2 or 4 baud
Typing speed1, 2 or 4 CPS (10 - 40 WPM)
ITU-R description100HF1B or 200HF1B
Bandwidth100 or 200 Hz
Modulation9-FSK (sequential and 2-tone concurrent)
ProtocolSynchronous unconnected characters
CharacterSetRestricted, similar to ITA-2

Software for FSK441 is called WSJT available from Joe K1JT. Because of the speed at which it operates, it is not practical to decode the received signal in real time. A digital recording is made (wave-file), which is then decoded and displayed.

This wide MFSK mode was designed for signal paths that may be only brief i.e. meteorite-scatter ‘pings’. FSK441 has been met with considerable success on 6m, and has been tried for moon-bounce as well.

FSK441 Summary:

Symbol Rate441 baud
Typing speed147 CPS (1470 WPM)
ITU-R descriptionK21F1B
Bandwidth2205 Hz
Modulation4-FSK (sequential, three symbols/characters)
Average Power100%
ProtocolSynchronous unconnected characters
Character SeRestricted, PUA-43 (similar to ITA-2)

Back to top


MT63 is a remarkable mode because of its wide bandwidth and usefulness in working in difficult conditions. It was ported from Linux to Windows with a graphical interface, by Nino Porcino IZ8BLY in 1999. Software tuning display for MT63 provides a script page and a waterfall diagram. The favourite frequency is with 14.110MHz using USB, 100 Watt transceivers are best to operate using 25 Watts because of the linearity requirements. Tuning on receive is done by monitoring the waterfall diagram. Decoding of the phase information is provided by a 64-bin FFT across the signal. The Walsh function provides a very clever error correction coding, FEC. Because of the large amount of processing required, operators leave good-sized gaps between overs.

MT63-1K Summary:

Symbol Rate10 baud
Typing speed10 CPS (100 WPM)
ITU-R description1K00J2DEN
Bandwidth1000 Hz
Average Power80%
ProtocolSynchronous unconnected FEC Walsh coding
Character SetASCII (7-bit)

Back to top


PacTOR became extremely popular in the early 1990’s, both for QSO’s and bulletin-boards use. It was developed to replace AmTOR. There is a new version called PacTOR II, which offers even better performance.

PacTOR uses two modes ARQ and FEC.

PacTOR Summary:

Symbol Rate100 or 200 baud
Typing speed6.6 CPS (66 WPM)
ITU-R description400HF1B, 600HF1B
Bandwidth400 or 600 Hz
Average Power80% (ARQ), 100% (FEC)
ProtocolSynchronous connected ARQ
Synchronous unconnected FEC
Character SetITA-5 ASCII (8-bit)

PacTOR II Summary:

Symbol Rate100 or 200 baud
Typing speedup to 30 CPS (300 WPM)
ITU-R description500HG1B(D), 500HJ2B(D)
Average Power80% (ARQ), 100% (FEC)
ProtocolSynchronous connected ARQ
Synchronous unconnected FEC
Character SetITA-5 ASCII (8-bit)

Back to top


PSK31 was developed in the mid 1990’s, as a replacement for RTTY by Peter Martinez G3PLX to bring it into the 21st century. Later he added a QPSK mode with better error correction code techniques. As a result, PSK31 as we have it today is available with lower power and narrower bandwidth than RTTY. The use of PSK31 now far outstrips use of all other digital modes.

Other versions of PSK31 modes: PSK63F, PSK127F, PSK250F and FSK31 are now in use. Many programs provide a clock phase meter display for tuning purposes, including a waterfall diagram.

PSK31 Summary:

Symbol Rate31.25 baud
Typing speed3.5 CPS (35 WPM)
ITU-R description63HF1B
ModulationDifferential 2-PSK (BPSK)
Average Power80%
ProtocolAsynchronous unconnected chat mode
Character SetVaricode, ASCII

Back to top


RTTY is one of the oldest digital modes, predating all but Morse and Hellschreiber, and has been used by Radio Amateurs just after World War II. In the 1950’s was in conjunction with a Creed Model 7 mechanical teleprinter. In the 1980’s special software was developed for the BBC micro-computer.

A modern RTTY is now available. The much used MMTTY is used world-wide. The pictorial displays makes for very easy tuning.

RTTY Summary:

Symbol Rate45.45 or 50 baud
Typing speed6.0 or 6.6 CPS (60 or 66 WPM)
ITU-R description270HF1B
Average Power100%
ProtocolAsynchronous chat mode
Character SetITU-R ITA2

Back to top

Image Modes

Slow Scan Television (SSTV) has been developed by Radio Hams in the 1950’s using Cathode-Ray-Tubes with very long persistence phosphors. It used line scanning being generated in a similar manner to that of fast TV. Around 1995 simple SSTV for the mass Amateur market arrived with DOS and Hamcomm interface software EZSSTV in 1990 modified to MSCAN.

A modern MMSSTV appeared in 2000 with three sequential scans red-green-blue.

STTV Summary:

Symbol Ratemode dependent, 200 – 500 baud (pixels/sec)
ITU-R description1K80F1C or 1K80J3C
ModulationAnalogue FSK
Average Powe100%

Facsimile (FAX) is used mainly by commercial companies for such applications: FAX weather maps and Satellite Images.

HF FAX Summary:

Symbol RateTypically 1000 pixels/sec
ITU-R description2K080F1C or 2K00J3C
ModulationAnalogue FSK
Average Power100%
Speed60, 90, 120, 180 LPM (120 most common)
IOC288, 576

Back to top

Advanced Digital Modes

These particular modes are subject for ongoing research and development. They require special and sophisticated hardware and used mainly for military purposes:

  • PC-ALE
  • STANAG 4285, 4529
  • Q15X25

G4GUO has developed a PC version of PC-ALE software. It is most effective for mobile communication networks.

PC-ALE Summary:

Symbol Rate125 baud
ITU-R description2K25HF1B
Average Power100%
ProtocolSynchronous connected ARQ
Synchronous unconnected FEC
Character SetITA2
STANNAG 4285, 4529

These are military standard modem specifications, intended for very high performance on HF. STANAG 4529 is a cut down version of 4285.


While not a communications mode in the conventional sense, exploration of the ionosphere using sounding is an interesting pursuit for Amateurs. The pioneer of this technique for Amateurs is Peter Martinez G3PLX. Developed by Pawel Jalocha SP9VR, Q15X25 (sometimes known as NEWQPSK), is derived from MT63, using a Motorola DSP 56002EVM chip set, may also be used for GPS.

Back to top

Hardware and Software

My recommendations for PC Interface, in order of preference:

1MyDEL CG AntennaSB-2000 Radio Interface
2TigertronicsSignalLink TM USB
3West Mountain RadioRIGblaster Plus

Items 1 and 2 are used mainly in the UK and available from ML&S around £100, you will need interface cables and connectors for your particular rig, at extra cost. (£5 - £45)

Item 3 is also used the UK but mainly prevalent in the US and available from Waters & Stanton for £135, plus cables etc.

All software to drive your receiver, transmitter or transceiver is provided with the equipment. Care must be taken to choose the correct COM port for the PC. All the interface units have opto-isolation giving high order of interference rejection.

Particular software I use and will describe in the next section.

Designed and developed by Simon Brown HB9DRV


Interface Software to interface TX/RX and PC.

Digital Master DM780:

Includes all the Digital Mode Software used in this document.

Please note. They are both free, also includes Satellite Data.

Back to top

Modes & Frequencies

Pre programmed Favourites:

Modes, Bands & Frequencies within the DM780 software.

MODESBandsFrequencies (MHz)
Contestia/  80 m  3.537 000
  80 m  3.582 500
  40 m  7.038 500
  40 m  7.072 500
  30 m10.133 000
  20 m14.075 000
  20 m14.077 000
  20 m14.106 000
  20 m14.108 000
  17 m18.102 000
  15 m21.086 000
  10 m28.070 000
CW/160 m  1.828 000
CW(KeyCmd)/  80 m  3.500 000
CW(WinKey)  40 m  7.000 000
MCW/  30 m10.000 000
  20 m14.00 0000
  17 m18.075 000
  15 m21.025 000
  10 m28.000 000
    6 m50.100 000
DominoEx-4/  80 m  3.564 000
DominoEx-8/  40 m  7.038 000
DominoEx-16  40 m  7.042 000
  40 m  7.072 000
  30 m10.148 000
  20 m14.076 000
  20 m14.078 000
Hell/160 m  1.804 000
Feld Hell/  80 m  3.574 000
Slow Hell/  40 m  7.039 000
Feld X5/  40 m  7.084 000
Feld X9  30 m10.134 000
Feld 105/  20 m14.063 000
Feld 245/  17 m18.104 000
Feld 80/  15 m21.074 000
MFSK-4/  160 m  1.838 000
MFSK-8/  80 m  3.580 000
MFSK-16/  40 m  7.037 000
MFSK-32/  30 m10.147 000
MFSK-64/  20 m14.072 000
  20 m14.076 000
  20 m14.078 000
  17 m18.105 000
  15 m21.080 000
  15 m21.082 000
  15 m21.084 000
  12 m24.929 000
  10 m28.080 000
  10 m28.082 000
  10 m28.084 000
    6 m50.500 000
Olivia 4/125  80 m  3.577 000
Olivia 4/250  80 m  3.582 500
Olivia 4/500  40 m  7.038 500
Olivia 8/2500  40 m  7.072 500
Olivia 8/125  30 m10.133 000
Olivia 8/500  20 m14.075 000
Olivia 8/1000  20 m14.077 000
Olivia 8/2000  20 m14.106 000
Olivia 16/2000  20 m14.108 000
Olivia 32/2000  17 m18.102 000
Olivia 64/2000  15 m21.086 500
  10 m28.026 000
PSK/160 m  1.807 000
BPSK-31/160 m  1.838 000
BPSK-63/  80 m  3.580 000
BPSK-125/  40 m  7.040 000
QPSK-31 USB/  40 m  7.070 000
QPSK-31 LSB/  30 m10.140 000
QPSK-63 USB/  20 m14.070 000
QPSK-63 LSB/  20 m14.080 000
QPSK-125 USB/  17 m18.100 000
QPSK-125 LSB/  15 m21.070 000
QPSK/  15 m21.080 000
  10 m28.120150
    6 m50.250 000
    6 m50.285 000
    6 m50.385 000
RTTY-45/160 m  1.820 000
RTTY-50/  80 m  3.580 000
RTTY-75/  80 m  3.582 000
  80 m  3.584 000
  40 m  7.040 000
  40 m  7.042 000
  40 m  7.044 000
  40 m  7.080 000
  40 m  7.082 000
  40 m  7.084 000
  30 m10.110 000
  30 m10.112 000
  30 m10.114 000
  20 m14.080 000
  20 m14.082 000
  20 m14.084 000
  20 m14.102 000
  20 m14.104 000
  15 m21.080 000
  15 m21.082 000
  15 m21.084 000
  12 m24.920 000
  12 m24.922 000
  12 m24.924 000
  10 m28.080 000
  10 m28.082 000
  10 m28.084 000
    6m50.500 000
RTTYM 4/125  80 m  3.577 000
RTTYM 4/250  80m  3.582 000
RTTYM 4/500  40m  7.038 000
>RTTYM 8/250  40m  7.077 500
RTTYM 8/500  30m10.135 000
RTTYM 8/1000  20m14.075 000
RTTYM 8/2000  20m14.077 000
RTTYM 16/500  20m14.106 000
RTTYM 16/1000  20 m14.108 000
  17 m18.102 000
RTTYM 32/2000  15 m21.086 500
RTTYM 64/2000  10 m28.076 000
SSTV/160 m  1.890 000
Martin 1/160 m  1.916 000
Martin 2/  80 m  3.730 000
Scottie 1/  80 m  3.783 000
Scottie 2/  80 m  3.845 000
Scottie DX/  80 m  3.857 000
P3/  40 m  7.030 000
P5/  40 m  7.033 000
P7/  40 m  7.045 000
  40 m  7.170 000
  40 m  7.172 000
  20 m14.227 000
  20 m14.230 000
  20 m14.233 000
  20 m14.236 000
  17 m18.160 000
  15 m21.334 000
  15 m21.337 000
  15 m21.340 000
  15 m21.343 000
  15 m21.346 000
  15 m21.349 000
SSTV/  12 m24.875 000
  10 m28.673 000
  10 m28.677 000
  10 m28.680 000
  10 m28.683 000
  10 m28.690 000
    6 m50.680 000
THOR 4160 m  1.838 000
THOR 8  80 m  3.580 000
THOR 16/  40 m  7.037 000
Throb -1/  30 m10.147 000
Throb -2/  20 m14.105 000
Throb -4/  17 m18.105 000
Throb X-1/  15 m21.080 000
Throb X-2/  12 m24.929 000
Throb X-4/  10 m28.080 000

(All the MODES are available within these Bands & Frequencies)

Back to top

Glossary & Software


ASKAmplitude shift Keying
AsynchronousGroups of data bits transmitted for Rx-clock to be resynchronised at the start of each group
ARQAutomatic Request Repeat
CRCCyclic Redundancy Check
DPSKDifferential Phase Shift Keying
FECForward Error Correction
FSKFrequency Shift Keying
MCUMulti-mode Control Unit
MFSKMultiple Frequency Shift Keying
PSKPhase Shift Keying
QPSKQuadrature Phase Shift Keying
SynchronousData bits transmitted & recovered using a clock derived from the data stream
TCP/IPTerminal Control Protocol / Internet Protocol
TNCTerminal Node Controller
VaricodeAlphabet represented by numbers with varying number of bits

Multi-Mode Digital Software

HamRadioDeluxe / Digital Master DM780

MIXW2        TrueTTY        HamScope        IZ8BLY Suite

Most of this software is free or shareware for a small fee. Worth a visit for loads of information & free software:

To anyone seriously venturing on trying out ‘Digi-Modes’ I recommend the most complete book yet written on the subject: ‘DIGITAL MODES For all occasions&rsquo by Murray Greenman, ZL1BPU, published by RSGB. (208 pages)

Back to top