LAST UPDATED: 14 JUNE 2020 DIGITAL / DATA MODES (DIGIMODES) Digital modes are becoming more and more popular on the amateur bands.  Over the past few years, the number of operators using one of the numerous forms of data (or digimode) has exploded.  For some, this has been the difference between being able to make contacts on air or not.  Because every PC, laptop and mobile device has built in sound capability, all you really need is your radio and an audio lead to connect from the sound device to the radio.  In fact , you can miss out the audio lead and use the microphone to pick up the sound from the speakers.  This, however, is not recommended as any other room sounds will be picked up and either transmitted or interfere with the received signal.  Use an isolated audio interface for the best results.  These can be purchased fairly cheaply on eBay, or you could make one your self.  With the surge of data modes, there has been an equal multitude of decoding software, some free, others not with which to receive and transmit these modes.  There are new modes being invented all the time and keeping track of these is could turn into a full time job!  One of the main problems encountered by the newcomer to digital modes (or digimodes as they are known) is how to identify what they are seeing / hearing.  Most of the decoding software uses a visual ‘waterfall’ display to facilitate easy tuning and identification.  With that in mind I went on the bands and captured images of the most common digital modes in use at the moment.  Below you will see images of each mode together with some brief notes on the mode.  The images show the most common variant(s) of the mode, although some have many different variants!  Bear in mind that this list is not exhaustive and there will be many modes not covered (yet) FT8 & FT4 (Franke-Taylor design, 8 (4) FSK modulation) FT8 Audio Samples (Click on desired format): ogg - mp3 - wav FT4 Audio Samples (Click on desired format): ogg - mp3 - wav 2017 saw the birth and meteoric rise in popularity of a new mode called FT8.  This is a mode that was co-authored by Nobel Prize Laureate Professor Joe Taylor, K1JT as part of the WSJT (Weak Signal (K1)JT) suite.  FT8 was originally conceived in answer to requests by Dxers for a ‘faster’ alternative to JT65, for use on 6m during the brief Es openings that sometimes occur at odd times during the year.  They may only last for a few minutes - sometimes not long enough to complete a QSO using JT65 (which can take upto 6 minutes).  Enter FT8.  FT8 has tx periods of 15 seconds (compared to the JT65 tx period of 60 seconds).  A whole QSO can take place in 1 min 30 (or even less), 4 times faster than was possible previously.  FT4 takes this one stage further, with periods of just 7.5 seconds.  The trade off is a drop in sensitivity by a few dB. In ‘Es’ openings, signals are usually strong so this is not much of an issue.  With the fast tx/rx periods, you can work many stations in just a few minutes.  We have now discovered that the 2m band has far more tropo openings than was thought, plus it has been a useful tool for random MS.  thanks again to FT8.  Because of the fast overs, a degree of automation has been added so that the operator does not have to get flustered trying to find the right button etc.  FT8 on 6m took off and it was discovered that the band was open far more than had been previously thought.  I spent a lot of time on 6m during 2017 and it certainly paid off.  DX was everywhere!  Even for my single element receiving station, I was hearing places that I could have only dreamed of a few years ago.  There is a slight trade off in sensitivity between JT65 and FT8, but most operators were willing to accept that for the increased QSO rates.  JT65 is still the best mode for sensitivity so for real low signal work, use JT65.  For Sporadic E, FT8 or FT4 seem to do the job just fine.  Now, I said FT8 was ORIGINALLY intended for use on 6m, which is true.  However, that did not stop the curious from trying it on HF.  Oh boy, FT8 was taken up with a fervour like never before.  Literally filling the 2-2.5kHz slot that had been settled on with hundreds of signals.  I was receiving 20 or more signals on each rx period.  As the software has been improved and the decoders carefully tweaked or rewritten, the number of successful decodes has increased.  Weak signals can now be decoded in very close proximity to much stronger signals.  FT8 has allowed operators with poor antennas and/or low power restrictions to work all over the world.  Even DXpeditions have realised how good FT8 is and are using it in conjunction with SSB, CW and RTTY - the usual DXpedition bread and butter modes.  The next development of the software was to add a ‘DXpedition mode’ (known as ‘Fox & Hounds, or just F & H) where several stations/signals can be worked at the same time.  Many DXPeditions are now using F & H mode as part of their planned operations.  The software builds a list of callers and the DX operator just works their way through the list.  I’ve not used F & H as the fox, obviously, but have seen how the hounds part operates, many times.  Below are some screen grabs of WSJT-X running FT8.  The grab below shows a very brief opening to the Czech Republic (or Czechia, as it is now known), Less than a minute.  This is an example of meteor scatter propagation.  The image shows a good burst of several seconds, enough to decode OK1DIG, who is very active on 2m (and other bands).  Since FT8, and some other newer modes such as FT4, MSK144 and FSK441, we have discovered that 2m and other bands are open far more often than previously thought.  Even a simple system will allow you to hear signals on 2m from all over the country, and very often, further afield.  I will cover this in more depth on my VHF DXing page.  Suffice it say that the invention of FT8 and other related digimodes has revolutionised amateur radio in the same, or even greater way than the introduction of SSB did.  FT8 has many ‘haters’, however it has many, many more ‘lovers’.  Love it or loathe it FT8 has made its indelible mark on the face of our hobby.  Above is a screen grab taken from my preferred FT8 software (JTDX).  I haven’t included the waterfall with this as I forgot to take a ‘grab’ of it at the time!  In red you can see the callsign D68CCC, a DXPedition to the Comoros Isl, off the coast of Western Africa, heard on the 15m band.  I have set indicators in JTDX to alert me of new countries and new grid squares (New DXCC are marked in red, new Grid locator squares are marked in yellow - obviously I am more interested in those on the VHF bands but if the station is from an interesting place I will log them).  The signal strengths are from about -12dB to -20dB so they range from fair to weak.  A signal of 0dB or above can be considered strong to very strong, easily strong enough for CW and probably SSB.  Signals below -17dB are likely to be too weak even for CW.  The limit of FT8 is around -24dB, that is VERY weak indeed.  For really, really weak signals, you need to use JT65, that can decode signals to below -26dB!  BPSK (Binary Phase Shift Keying) PSK, or Phase Shift Keying started the digimode revolution in amateur radio.  Peter Martinez, G3PLX devised the protocol for PSK and once it was released into the ham community, it became an instant hit.  As this was a new way of communicating, it took a while before the majority had figured out how to use it.  Seeing a ‘waterfall’ of signals was confusing to us, as we were used to ‘single signal’ working.  Click on a signal and you could then communicate with that station - wow!  There is a wealth of information on the web regarding BPSK (Binary PSK) and QPSK (Quadrature PSK).  There are a multitude of multimode programs that can decode/encode PSK, and, usually, many others too.  For the sake of clarity, I will refer to BPSK as ‘PSK’ and QPSK will remain ‘QPSK’.  Most users do not use the prefix ‘B’ when referring to BPSK.  BPSK variants: BPSK31 Audio Samples (Click on desired format): ogg - mp3 - wav The most commonly used variant of PSK is PSK31.  It is so called because the speed of the transmission is 31 Bd (the full name is Baudot, but is also shortened to ‘Baud’).  The actual speed is 30.5Bd, but it was thought ‘PSK31’ sounded much better than PSK30.5!  Because PSK31 has a signal bandwidth of only 31Hz, many signals can fit into the same bandwidth that would be occupied by a single SSB signal (2.4kHz approx).  It is quite common to see 15 or more signals on a 2.5kHz waterfall display.  The image below shows that a good number of signals can inhabit a single 3.5kHz channel without causing problems to other users.  The example below shows 25 PSK signals, mostly PSK31, with room to spare.  You could probably fit another 25 signals in there, although it might get tricky to find a space!  A ‘clean’ BPSK31 signal.  This is how your signal should look!  Here are a couple of BPSK31 signals that are badly distorted.  This is probably due to overdriving.  Reducing the input to the soundcard or reducing the output level would improve the quality of this signal.  Note that although some way from the adjacent signal on the left, the distorted signal is sufficiently wide to cause interference to the other signal.  These stations have unstable signal and are drifting badly.  A stable and ‘clean’ transmitter is vital when using narrow modes such as PSK31 and it’s variants so as not to cause QRM to nearby stations BPSK63 Audio Samples (Click on desired format): ogg - mp3 - wav BPSK125 Audio Samples (Click on desired format): ogg - mp3 - wav PSK63 has gained popularity, with many programs now supporting this mode.  BPSK63 is now the commonest variant of the PSK modes.  The pro’s for this mode are the fact that data is sent and received at twice the rate of normal PSK31, so is great for chatting and contest exchanges.  The con’s to this mode are the increased bandwidth required over PSK31, the increase in power required to maintain the same level of copy as PSK31.  PSK63 can be identified quite easily as it looks like a ’fat’ PSK31 signal!  Basically, if you double the speed of transmission (31 vs 63 Bd) you will also double the bandwidth required for that transmission (31 vs 63Hz, approx).  If you jump to PSK125, then it is a very fast mode, but takes up 125Hz of bandwidth.  Other variations of PSK31 are PSK16 (half bandwidth/speed of PSK31); PSK125 (4 times bandwidth/speed) and other experimental variations such as PSK10 (to be found in MultiPSK) and even PSK250.  The other common variant of BPSK31 is QPSK31, (the ‘Q’ stands for ‘Quadrature’, rather than the usual B which is ‘Binary’ Phase Shift Keying), which is sideband dependent (i.e. both transmitter and receiver must be using the same sideband) but is not in common use despite it’s superior decoding ability during poor conditions.  Here we can see the difference between a PSK31 signal and a PSK125 signal.  The PSK125, although much faster, takes 4 times the bandwidth and requires 4 times the power for the same s/n ratio as PSK31.  It is a great mode when conditions are good and signals are strong, especially on the higher bands where there is more space.  There are one or two multimode packages that support PSK250, but I don’t recall ever seeing it used on air.  It would appear as a big, fat signal that doesn’t last very long (during the course of a usual QSO, where overs are not that long, even when chatting).  Another seldom seen variation is PSK10, which I think only MultiPSK supports.  A slow, very narrow mode.  Again, I don’t recall seeing it used on air.  All of these modes have their QPSK ‘Twin’: QPSK (Quadrature Phase Shift Keying)

Here is a waterfall shot of QPSK63 (the wider of the signals).  If you compare it to the BPSK63 signal above, and also on the left of the picture, you can see there appears to be more information contained within the same signal, this is the easy way to visually tell QPSK from BPSK.  Differences between Binary and Quadrature PSK: Binary PSK is sideband independent, meaning the transmitting station can be using either USB or LSB to send the data and the receiving station can decode the data no matter which sideband is used.  Convention sees most digital modes using USB irrespective of frequency - even RTTY is more often than not transmitted on USB these days, simply because the software tends to default to USB.  In the ‘old’ days of RTTY, when the methods used to generate it were mainly mechanical rather than via PC soundcard (years before the PC was invented), it was always transmitted on LSB. 

QPSK, however, IS sideband dependent and needs the receiving station to be using the same sideband as the transmitting station. 

BPSK uses two phases to encode the data contained in the reference signal, namely +180 degrees and -180 degrees. 

Quadrature PSK, however, uses four phases to encode the reference signal.  These phases are: +45; -45; +135 and -135 degrees. 

QPSK transmits two bits per character/symbol, whereas BPSK uses just a single bit per symbol.  Using QPSK, you can double the data throughput but keep in the same bandwidth.  This means a QPSK63 signal could take up only 31Hz, instead of the usual 63Hz (approx).  A downside to this increase in speed is that decoding errors are more likely. 

the main variants of QPSK are: QPSK31, QPSK63 and QPSK125 (all USB - very rarely is LSB used).  The original, complete, description of the differences between BPSK and QPSK can be found on Quora.com in an answer submitted by Joao Victor Carvalho SSTV ( S low S can TV ) SSTV Audio Samples (Click on desired format): ogg - mp3 - wav Slow Scan TV has been popular for many years, although the vast majority these days is computer generated.  The most common modes are Martin (1 and 2) and Scottie (1 and 2).  Robot still has a following (Robot images are quite small and are usually green in colour).  Most SSTV programs handle these modes and others too.  The received pictures are built up line by line over the course of nearly a minute so you need to be patient!  Quality can be very good, even over long distance paths.  Here are two pictures received by me — the Middle one is from Hawaii (KH6AT) and the right hand one is from Sweden (SM7UZB).  The leftmost image shows an analogue SSTV signal on the waterfall.  RTTY (Radio TeleTYpe) RTTY Audio Samples (Click on desired format): ogg - mp3 - wav The ‘original’ data mode.  RTTY (pronounced ‘Ritty’) has been around for many, many years and is still just as popular.  Years ago the only way to get on RTTY was to use a mechanical terminal unit such as the Creed ‘7’ series, which were big, noisy and messy.  This is known as FSK or Frequency Shift Keying.  These days, virtually all RTTY is done by the computer/soundcard combination (AFSK - Audio Frequency Shift Keying).  Amateurs (hams) use 45.45 baud (the speed) with 170Hz shift (between mark and space).  Commercial stations commonly use 50 or 100 baud with shifts of 425 or even 850Hz.  Most software caters for differing speeds and shifts.  Unlike most digital modes, RTTY is transmitted on LSB.  Although, with the almost universal use of soundcard software, you can use USB and invert the signal in the software (most software is intelligent enough to do that sort of thing automatically).  Ideally, you would use a ‘twin peak’ filter, with a peak over the ‘mark’ tone and one over the ‘space’ tone.  The high tone is 2125Hz (Europe) or 2295Hz (America), with the lower tone 170Hz below those (1955/2125Hz).  MFSK (Multiple Frequency Shift Keying) MFSK8 Audio Samples (Click on desired format): ogg - mp3 - wav MFSK16 Audio Samples (Click on desired format): ogg - mp3 - wav MFSK is similar to the commercial Piccolo system.  MFSK is very good under poor propagation conditions.  The usual variant of MFSK is MFSK16, but other types such as MFSK 8 are in development, along with other modes similar to MFSK (such as Domino).  MFSK is sideband dependant, so you must have your receiver set to the correct sideband in order to decode it properly.  Also tuning is quite critical, although AFC helps somewhat.  The below left image is of an MFSK16 signal, and the below right image is of an MFSK32 signal (which as you can see is nearly 500Hz wide, twice as wide as an MFSK16 signal).  MT63 (Multi Tone 63) MT63 Audio Samples (Click on desired format): ogg - mp3 - wav MT63 is an orthagonal frequency division multiplexed (or OFDM) data mode, which was developed by SP9VRC.  MT63 uses 64 different tones spread over the bandwidth of up to 2kHz.  MT63 is very robust, not only to propagation variations, but is also very tolerant to mis-tuning.  The signal can be over 100Hz off frequency and still achieve 100% copy.  The tradeoffs however are bandwidth and speed.  Because of the wide bandwidth, MT63 is usually confined to 14MHz and above, where there is sufficient space to accommodate it.  HELLSCREIBER (Hell, Feld Hell) HELLSCREIBER Audio Samples (Click on desired format): ogg - mp3 - wav Hellschreiber (or Hell as it is commonly known) is a bit different from most other data modes.  When receiving a Hell signal, your eyes do the filtering!  The decoded text is displayed on a ‘ticker tape’ display (as shown in the picture).  Hell has a very distinctive ‘grating’ sound and is a narrow band mode.  The Hell signal is on the left of the picture (with the green flag above it), with an MFSK signal on the right—note the bandwidth required for the MFSK signal compared to the Hell signal.  Even weak signals can be decoded as your eye/brain combination can ‘fill in the blanks’ where the signal fades. 

Here is a waterfall of a Hell signal, together with a decode (showing how it appears on screen) PACKET (AX25) Packet (HF - 300bd) Audio Samples (Click on desired format): ogg - mp3 - wav HF mailboxes etc.  use packet to forward messages to users.  The usual data rate on HF is 300 baud, with 1200 and 9600 baud being common place at VHF and UHF.  The picture shows a mailbox/BBS in Turkey negotiating with a BBS in the UK.  The short burst at the bottom of the picture is header and callsign information whereas the longer burst is the actual data.  Several of these packet BBS/mailboxes can be heard chirping around 14.1MHz.  Some VHF/UHF satellites have AX25 transponders, including the International Space Station (ISS), which occasionally transmits either Packet at 1200bd or SSTV images.  PACTOR (PACket amTOR) Pactor Audio Samples (Click on desired format): ogg - mp3 - wav Pactor is another digital mode used by HF mailboxes,etc to forward messages to users.  Pactor I combines elements taken from both Amtor-ARQ and Packet radio.  Pactor I is still used by hams all around the world, as well as by some Government (and Non Government) and diplomatic departments from various countries.  Pactor I has a data throughput of 200 Bd.  The mode was invented way back in 1990 by two German hams, DL6MAA and DL4KV.PACTOR has had a lot of bad press recently, mainly due to the actions of a few inconsiderate operators who are apparently causing interference deliberately to existing users of the digital sub bands.  I cannot comment on this as I have not experienced it personally.  The picture shows the PACTOR signal trying to establish contact.  Once established the transmission of data can begin.  Because PACTOR uses error correction, it can take quite a time to send a message particularly over a less than perfect path—but the transmitting station will keep trying until the message is received perfectly.  The picture is of a PACTOR 1 signal, however there are PACTOR II, III and IV variants, but these require hardware encoders/decoders.  THROB Throb 1 Audio Samples (Click on desired format): ogg - mp3 - wav Throb 2 Audio Samples (Click on desired format): ogg - mp3 - wav Throb 4 Audio Samples (Click on desired format): ogg - mp3 - wav Throb is one of the newer digital modes and although it can be heard, it is nowhere near as popular as other modes such as PSK31 or RTTY.  The name Throb actually describes the sound the mode makes - the sound fades up and down in intensity, just as a throbbing pain would.  As with the other modes, there are various variations of Throb, 1 throb/second; 2 throbs/second and 4 throbs/second.  1 throb is the slowest and 4 is the quickest.  Throb is actually quite a slow mode and is therefore probably quite resilient to the effects of fading etc.  although is does take quite a time to complete a contact!  Throb 1 Throb 2 Throb 4 OLIVIA Olivia Audio Samples (Click on desired format): ogg - mp3 - wav Olivia is a digital mode developed back in 2003 by Pawel Jalocha and is extremely resistant to fading and QRM.  I can get full copy on stations that are barely audible (even ones that fade down to almost zero seem to still print well).  Signals down to -10, even -13dB can be resolved.  Being resistant to fading, flutter, even under auroral conditions, a conversational QSO can be made under some of the most challenging HF conditions.  Other modes may be able to decode signals deeper in the noise, but those tend to not be modes where you can chat to your QSO partner - they are more ‘Rubber-Stamp’ modes where information is sent in a pre-determined sequence and is of a set content (such as JT65, FT8, etc.).  As with other modes, Olivia has many different variants each having a different bandwidth (from 125Hz to 2kHz) and different number of tones (from 2 right up to 256) Out of the possible 40 variants, only a few are used.  Olivia can be very slow (in the order of 2-3 characters per second) but a slow contact is better than none at all!  In the below pictures, the 8/250 indicates 8 tones over a 250Hz bandwidth and 32/1000 is 32 tones over a 1kHz bandwidth.  To avoid interference to other stations is it usual to start an Olivia transmission on a full kHz (i.e. 14.108.0 rather than 14.108.3, for instance).  CONTESTIA Contestia Audio Samples (Click on desired format): ogg - mp3 - wav Contestia is very similar to Olivia, and was developed in 2005 by Nick Fedoseev (UT2UZ), the co-author of the MixW series of multimode decoding software.  It is not, quite as robust as Olivia, but the plus side is that the speed of transmission is faster.  Compared to Olivia, Contestia needs signals to be around 2-3dB stronger to get the same results.  The image is of a Contestia 4-250 signal from RW3AS on 20m. JT6M (Joe Taylor 6 Metres) JT6m Audio Samples (Click on desired format): ogg - mp3 - wav JT6m is another mode / protocol from the K1JT stable.  JT6m was designed specifically for the 6m band and to take advantage of the various propagation enhancements that are prevalent on that band.. FSK441 (Frequency Shift Keying 441) FSK441 Audio Samples (Click on desired format): ogg - mp3 - wav FSK441 is a weak signal protocol developed by, once again, Professor Joe Taylor - K1JT.  FSK441 uses message frames of 441bits.  The primary use for FSK441 is to make QSO’s during meteor scatter events.  Tthese events are fairly common, with several major showers taking place each year, as the travelling earth passes through the debris of various comets and asteroids.  FSK441 has only been in use for a few years, but has enabled even modest stations the chance to work some very interesting DX on 50, 70, 144 and 432MHz.  The difficulty of making a QSO via meteor scatter increases with frequency, so at 50MHz, it is relatively easy, but at 432MHz, it is pretty difficult and requires a good station and patience.  Below is a screen shot of S54T in Slovenia calling CQ on the 2m band, using FSK441.  I was lucky enough to be monitoring and heard several ‘pings’ from him.  My 2m station consists of an Airspy SDR receiver and a 5 element yagi at about 6m above ground.  When beaming towards S5 land (in fact anywhere between North and almost South) I am beaming straight through the tiled roof of my or my neighbours house, so not ideal.  That said, I have been amazed at what I have picked up on 2m. This is down to, in no small part, to K1JT and his amazing software - or rather the invention of the weak signal modes tailored to each type of propagation and band.  FSK441 is a high speed meteor scatter communication mode.  FSK441 uses a baud rate of 441Bd.  Maximum propagation distance: 2,250 km Transmitting: FSK441 is designed to transmit the same message over & over to give the signals a chance to bounce off a good meteor coming through the atmosphere.  When receiving FSK441 from distant operators, the signals will come in at varying burst lengths of varying strength.  Some can be as long as 10 seconds, and as short as a few hundred milliseconds.  FSK441 is generally used on the 2-meter and 70-centimeter amateur bands.  MSK144 (Minimum Shift Keying 144) MSK144 is another mode released from the K1JT stable.  This is also designed for weak signal working on the VHF bands.  MSK stands for minimum shift keying, a form of continuous-phase frequency-shift keying (FSK) with shift equal to half the baud rate.  MSK144 uses message frames of 144 bits and modulation at tone frequencies 1000 and 2000 Hz to transmit channel symbols at keying rate of 2000 baud.  Below are descriptions of the modes/protocols, by Joe Taylor, that can be found in the WSJT-X software suite: JT4, JT9, JT65, and QRA64 use nearly identical message structure and source encoding (the efficient compression of standard messages used for minimal QSOs).  They use timed 60-second T/R sequences synchronized with UTC.  JT65 and QRA64 were designed for EME ("moonbounce") on the VHF/UHF bands; JT65 has also proved popular and effective for worldwide QRP communication at HF.  JT9 is optimized for the LF, MF, and HF bands.  It is about 2 dB more sensitive than JT65 while using less than 10% of the bandwidth.  Using either JT9 or JT65, world-wide QSOs are possible with power levels of a just a few watts and small/compromised antennas.  JT4 and QRA64 are optimized for EME on the VHF and higher bands, and especially the microwave bands from 2.3 to 24 GHz.  FT4 and FT8 are operationally similar but use T/R cycles only 7.5 & 15 s long, respectively.  MSK144 is designed for Meteor Scatter on the VHF bands.  These modes offer enhanced message formats with support for nonstandard callsigns and even some popular contests.  JT65 - JT9 (Joe Taylor 65 tones (9 tones) JT65A Audio Samples (Click on desired format): ogg - mp3 - wav JT9 Audio Samples (Click on desired format): ogg - mp3 - wav JT65 is another mode released from the K1JT stable.  JT65 is an MFSK mode that uses 65 tones of differing frequency.  JT65 has three sub modes: (T65A, JT65B and JT65C. The difference between the three sub modes is the frequency shift between the tones.  JT65A uses 2.7Hz; JT65B uses 5.4Hz and JT65C uses a 10.8Hz inter-tone shift.  The transmit and receive periods for JT65 are 47.8 seconds, but each period starts on the next whole minute - this means there are approximately 12 seconds where the PC can decode the received signal, or be in standby for the next receive period, having just transmitted.  JT65A is mainly used on HF and 6m. JT65B is the primary mode for EME communication on 2m. JT9 is similar to JT65 but uses only 9 tones and consumes about 10% of the bandwidth of a JT65 signal.  Not only does JT9 use rrmuch less bandwidth, it is also about 2dB more sensitive than JT65.  JT9 is a very good mode for extremely weak signals.  For one of the most (if not THE most) comprehensive signal identification guide/archive, visit: https://www.sigidwiki.com/wiki/Signal_Identification_Guide The guide contains details and samples of many, many digital and analogue modes, including amateur, utility, commercial, professional and military types.