Digital Modes

LAST UPDATED: 1st January 2018


Digital modes are becoming more and more popular on the amateur bands. This is mainly due to the following reason: Affordable home PC’s with built in soundcards. This has brought forth a multitude of decoding software, some free, others not. There are new modes being invented all the time and keeping track of these is turning 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.

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 ‘flavours’! I will add to this list as and when I hear/identify a new mode that is being used on a regular basis (last popular ‘new’ one is Olivia which wasn’t around when I did this page on my original site) 

Click on the name of the mode (where the name is underlined) to hear an mp3 of how the mode sounds on air (these are to give you an idea of how that mode sounds, not for analysis purposes) I have included some sound files of mode variants - more to come as I find them).


PSK, or Phase Shift Keying has become the most popular of the newer digital modes. There is a wealth of information on the web regarding BPSK (Binary PSK) and QPSK (Quadrature PSK)

Because PSK31 has a bandwidth of only 31Hz, many signals can fit into the same bandwidth that would be occupied by an SSB signal (2.4kHz approx.). It is quite common to see 15 or more signals on a 2.5kHz waterfall display.

20m busy 2

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.

bad psk31

Here we see a station that has an unstable signal and is 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




PSK63 is gaining popularity, with many programs now supporting this mode. 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 and that not all software decoders support PSK63.  PSK63 can be identified quite easily as it looks like a ’fat’ psk31 signal!


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 is an 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 tell QPSK from BPSK.

psk31 and 63

This picture shows the bandwidth difference between PSK31 and PSK63, PSK63 being the wider signal.

pks125 and 31

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.


SSTV (Slow Scan TV)

Slow Scan TV has been popular for many years, although the vast majority these days is computer generated. The most common modes are Martin and Scottie. Robot still has a following. 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 topmost one is from Hawaii (KH6AT) and the bottom one is from Sweden (SM7UZB).



RTTY (Radio Teletype)

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. These days, virtually all RTTY is done by the computer/soundcard combination. Amateurs (hams) use 45 baud (the speed) with 170Hz shift (between mark and space). Commercial stations 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.




MFSK is similar to the commercial Piccolo system. MFSK is very good under poor propagation conditions. The usual variant of MFSK is MFSK 16, but other types such as MFSK 8 are in development, along with other similar modes 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 top image is of an MFSK16 signal and the lower image is of an MFSK32 signal (which as you can see is nearly 500Hz wide, twice as wide as an MFSK16 signal).




MT63 is very robust and offers 100% copy when other modes fail. The tradeoffs however are bandwidth and speed. MT63 is quite slow and occupies anything from 500Hz to a full 2kHz (which is still less than a single voice channel). Because of the wide bandwidth, MT63 is usually confined to 14MHz and above, where there is sufficient space to accommodate it.

mt63 long2_308x85



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)

feld hell 2feld hell



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.




HF mailboxes etc. also use PACTOR  to forward messages to users. 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 2 and 3 variants, but these require hardware encoders/decoders.




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. 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!

throb1-1_76x111throb2 - 16_78x108throb4_99x102 

 Left to Right: Throb 1; Throb 2; Throb 4 (click each type to hear the different sounds).



Olivia is a fairly new digital mode and it seems to be 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). As with other modes, Olivia has different variants each having a different bandwidth (from 500Hz to 2kHz) and different number of tones. 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).


Here are some waterfall shots of some other Olivia modes:

olivia 8-250
olivia 32-1000



Contestia is another very new mode to be found on the ham bands. It is not, as yet, very popular and so far I have heard only one station transmitting this mode. Again I have included a sound file and a waterfall capture so that you may see what it looks and sounds like. This image is of a Contestia 4-250 signal from RW3AS on 20m.



JT6M is a specialised mode found in the WSJT software suite  (from Professor Joe Taylor, K1JT) designed for weak signal working (such as EME—Moonbounce and Meteor Scatter). JT6M is the favoured mode for MS and Sporadic E and can be heard on 6m around 50230.  I have done some monitoring recently using JT6M and have seen full decodes from stations that were not audible to me by ear, which I think is quite impressive!



Similar in principle to the broadcast DRM signals heard on the SW broadcast bands. DRM is a very experimental mode at the moment, with the main exponents being found on 80m around 3733kHz. I have not had much success with this mode as yet, despite having good signal levels. The signals need to be very clean and strong in order to decode. Pictures can be sent using DRM, but time will tell as to how/if this mode grows in popularity. Below is a waterfall ident from DD9ZO, sadly this station was not strong enough to decode. This mode does not seem to have taken off in the way that others have, mainly I think due to the fact that it requires a very strong and noise/fade free signal in order to decode. This is much like broadcast DRM. Unfortunately, the disadvantage with this mode and most other digital modes is that the signal is either fully readable or not copiable at all. With analogue signals (and some digital modes) you can usually fill in the blanks when you get fading or noise on the signal, also they are copiable when they are barely audible. Some newer modes do work very well at signal levels that are at or below the threshold of human hearing (WSPR for instance, which is mode that has only been around for a few months but unfortunately it is a one way mode, that is it is a beacon mode rather than a ‘conversation’ mode). 




If you tune on 14.233 you may well hear a strange signal that sounds very similar to the HAM DRM signals mentioned above. This will be one of the new Digital SSTV modes. Like all DRM modes, Digital SSTV produces excellent, noise/distortion free pictures which can be in high definition. However for this to occur, the received signal needs to be very strong and relatively free from noise etc. If the program loses any part of the signal, due to a noise spike or a brief fade, the whole picture is lost. This is the big disadvantage with this mode on HF, it really is all or nothing. The software I am using to decode this mode is called  ‘EASYPAL’ and is available from . If you don’t want to transmit a picture, you can send short text messages in the ‘waterfall’. I haven’t used this program much so don’t know all the ins and outs but it’s good to be able to decode this new mode. Below is a waterfall grab of a digital SSTV signal (as seen in the MixW waterfall)

hd sstv-4

Example of waterfall text received in EasyPal

hd sstv-5

Digital / HD SSTV picture received on 14.233MHz in August 2010


Here are some more pictures captured using EasyPal, on both 20m and 80m. I am finding that there is more activity now than when I originally wrote this piece. The pictures are of stunning quality and, as they are digital, there are no traces of noise, QSB or any of the other problems that affect analogue SSTV pictures. The downside is that with these you either get the entire picture, or nothing at all - plus the transmission time seems rather lengthy. You do need a strong/clean signal in order to use digital SSTV, but it is well worth it. There are some received pictures I cannot show on this site as they are rather ‘risqué’ and show women in various states of undress - pleasing to the male eye, perhaps, but not really suitable for ham radio.

These were received on 80m (again, note the quality of the decode, even on the noisy 80m band at night:


111219183345-ScreenHunter_07 Sep1


And here are some from 20m:




Here is another of the new modes which can be decoded by many different software packages. Domino is another mode that uses MFSK (Multi-Frequency Shift Keying). MFSK sends data using many different tones, sent one at a time. As with ‘normal MFSK, it has excellent performance but was developed specifically to cope with the noisy conditions of the lower HF bands. For more information and technical details, visit:

As with the other MFSK modes (such as MSFK16, Throb, Olivia etc.) Domino is used with different parameters, the best mode variant to use is dependent on band conditions.

 domino1 - 8_109x121domino1 - 16_169x106domino2 - 8_111x102domino2 - 16_175x108domino3_169x95DominoEx

Above Left to right are:

DominoF 1-8; 1-16; 2-8; 2-16, Domino 3 and lastly DominoEX. However DominoEX (click to hear sound file) has superceded DominoF. Like DominoF, DominoEX has a multitude of variants to suit various bands/conditions..


Thor is a new mode and is very closely related to DominoEx. It is an extremely robust mode and is well suited to HF weak signal conditions. A single carrier of constant amplitude is stepped between 18 tone frequencies in a constant phase manner. This means that no unwanted sidebands are produced, and it does not require the same kind of linearity requirements as some modes (PSK in particular). The tones change according to an offset algorithm which ensures that no sequential tones are the same or adjacent in frequency, considerably enhancing the inter-symbol interference resistance to multi-path and Doppler effects. Thor, like other similar modes has a variety of speeds and tones to choose from, dependent on band conditions and signal levels. The modes are Thor 4, 5, 8, 11, 16 and 22. Speeds vary from the equivalent of 14wpm right up to 78wpm for Thor 22. and bandwidths vary from 173Hz up to 524Hz.

THOR 16 better 2

This is a waterfall grab of a Thor 16 signal.


JT65 was developed originally as part of the WSJT weak signal modes software package by Joe K1JT. JT65 can also be decoded by other packages, such as MultiPSK. The screen grab below is taken from MultiPSK. JT65 has found a use on HF and can be found around 14.076MHz and 21.076MHz amongst others. Signals that are virtually inaudible can give perfect copy so its  performance is excellent on the noisy HF bands. The transfer rate is slow, as are most modes that excel in low signal decoding. I am now monitoring JT65 most days and am amazed how well signals come through, day after day!

jt65a in multipsk 2
jt65 2
jt65 1


This is a screenshot of another JT65 program. This is JT65-HF by W4CQZ, a free decoder that is specially written for those of us that like to play around with JT65 on the HF bands. I have been using this for quite a time now, and I am very impressed by it. I like the interface, it is easy to use and easy to set up. It will decode multiple signals at the same time and stores the results in a CSV (comma separated values text) file for later analysis. Another useful feature is that, like DM780, it sends spots to the PSK Reporter website and they are displayed on a map. You can interrogate the system to display all spots seen by any particular callsign etc.  As you can see from the above screenshot JT65 works very well on HF and I have heard signals from all over the world from stations using fairly simple equipment and low power. Also the program reports to the RB (reverse beacon) network, which is found at: . The above screenshot shows stations in Brazil, UK, Netherlands and Asiatic Russia, all on a very quiet 10m band.

JT65 grab

This screenshot shows the spots my receiving station has sent to the PSK reporter network over a 24 hr period, using JT65a. As you can see, all four corners of the world have been heard! There are some stations active from Africa, mainly in South Africa (ZS) and it is not uncommon to hear them - however none were active then this screenshot was taken.

I have decided that in 2011 I will be devoting a fair amount of time to JT65a (each year I choose a particular mode or band that takes preference - in the past I have done CW, 160m, PSK31, WSPR, 6m and now is the turn of JT65). There has been a marked increase in JT65a activity on the HF bands, mostly due to the efforts of Joe and his excellent JT65-HF software. I am intending to promote activity on this weak signal mode wherever possible. When using this mode, it is advisable to keep the transmitter power to 50w or less or no more than half the rated output of your transceiver. Most of the time 20-30w is more than adequate and quite often contacts over amazing distances can be achieved using just a couple of watts. It is interesting to note that even when a band appears to be closed, the chances are that there may well be a JT65 path open. If you have restricted antennas, power or both, this could be the mode for you. Signals that are 24dB below the noise level can be decoded with relative ease.

Joe is constantly developing the software and releases new versions regularly. Each release sees a further improvement in functionality, but without sacrificing ease of use.

To download the latest version of the software (v1.093), click HERE.


This introduction is taken from Joe Taylor (K1JT)’s WSPR 2.0 online user guide. WSPR (pronounced "whisper") stands for “Weak Signal Propagation Reporter.” The WSPR software is designed for probing potential radio propagation paths using low-power beacon-like transmissions. WSPR signals convey a callsign, Maidenhead grid locator, and power level using a compressed data format with strong forward error correction and narrow-band 4-FSK modulation. The protocol is effective at signal-to-noise ratios as low as –28 dB in a 2500 Hz bandwidth. Receiving stations with internet access may automatically upload reception reports to a central database. 

For more detailed information on WSPR and to download the programs, see the WSPR website or the WSPRnet website where the database etc. are hosted.

wspr waterfall
wspr screen grab3


Here are the USB dial frequencies for WSPR:


Frequency (MHz)




























Below is a summary of stations heard on WSPR over course of a month (27 November to 27 December 09).

30m has been the band I have spent most time monitoring as can be seen by the fact I have decoded over 270 stations on that  band alone. What I have found strange is the lack of African stations - not a single one has been decoded to date. I guess it hasn’t caught on over there yet. Hopefully as the mode develops and interest increases some stations will take it up as it would be interesting to see how the propagation paths to Africa open and close during the course of a day or month. Asia is quite sparse too here. I know there are stations on from Japan etc. but I am not hearing them here very often. Same with Australia. No path to VK for me yet. It is nice to see some North American’s on 80m, proving that there has been a path most nights and it should be workable with modest powers and antennas. If I can hear a 1 watt American station on 80m WSPR at a reasonable level,  then I should be able to hear ones running 100w of CW/SSB or 30w of PSK with little problem.


By Continent











































Over the past few weeks I have been transmitting on WSPR (and a few other modes) with 5 watts or so into my inverted Vee and have been very impressed with the results. I still feel that I would be better with proper dipoles for each of the main bands I am interested in and I will hopefully work on that during the summer.


I have now been using the OCF dipole/Windom arrangement for a few weeks on various bands/modes and can report that it works well although it does not have quite the same impact on 30 and 40m as the G5RV. The reason is because tthe OCF is designed for use on 20m and above so operation below 14MHz is a compromise. That said, it still radiates a fairly good signal on 30m as borne out by the WSPR reports I have collected.

So far this year I have been heard in 56 entities, which are:


















Ballearic Isl


Canary Isl










Reunion Isl




Northern Ireland
















Puerto Rico










Czech Republic






Faroe Islands






















Asiatic Russia


European Russia






















New Zealand


South Africa

As you can a see there are a spread of countries from all continents, which is gratifying as it means that I am at least radiating some sort of signal in every direction.

Here is a summary, by band, of where my WSPR signals have been heard (The term ‘ODX’ refers to ‘longest distance’, so in this table ODX means the furthest that I my signals have been heard):








Hrd by number of stations







ODX (km)







Avg Distance (km)







Hrd in DXCC







Lowest SNR reported







Highest SNR reported







WW QRA locator Squares:







So from this I can see that on 10m there have only been reports from single hop sporadic E openings and the average distance on that band is quite short at just under 800km. This short distance is due to the MUF being high and the skip distance decreasing as a result of the higher angle reflections. I have not spent much time on 10m because the high MUF sent me packing up to 6m where the band would usually be open. There have been multi-hop Es on 10m, but I have been on 6m when these have been about! On the 20 and 30m bands there is not much to choose between them and the average distance is about that of a single F-layer hop. The 40m average is about half the distance so my antenna must have quite a high angle of take off to reflect at this short distance. Experiments like this are interesting in assessing antenna effectiveness. I can see that even though my antenna is 3/4 of a wavelength above ground, it is physically short (a quarter wave in length, but the feed arrangement does not make it an efficient DX antenna on this band). However it does seem to be suited to local/semi local (i.e. within the UK and Europe) working - with the odd longer distance QSO possible when conditions are favourable. Looking at the signal to noise ratios (SNR) there is a huge difference between the strongest and weakest (44dB - that means that the best SNR is over 20,000 times stronger than the worst SNR!). -33dB is extremely weak and must be right at the very limit of the decoding capability of the software. To quantify this and put it into figures that are more easily understood, say I was running 1 watt output and my signal was received with an SNR of -33dB, in order for me to improve that report by 10dB, I would, in theory,  need to increase my output by 10 times (which is 10dB), therefore I would need to run 10w. To increase my received SNR by a further 10dB another 10 times power increase is needed - taking my output power to 100w (10x10w). A further 10dB increase (giving a 30dB overall increase) would take the power output to 1kW (1000w) or a 1000 times our starting power. Reversing the situation, let’s see how that kind of change would affect the s-meter of a receiver. S-meters are not usually that accurate and calibration can be all over the place. there is a standard though and that is 6dB per s-point, so if we say the worst SNR gave a reading of s1, the best SNR would indicate just over s7. If we were talking about pure signal strength this would be the case, but with Signal to Noise ratios this would not be true as we are talking about dB above the noise level and dB below the noise level. The human ear can decode CW signals down to about -15dB or possibly -18dB SNR but certainly not much, if at all, lower than that (and believe me, that is a weak signal and takes all your concentration to hear it!). That is still a good 15-18dB above the weakest SNR that WSPR has decoded my signals at!


ROS is a fairly new mode that is in it’s first year or two of use. ROS uses multiple tones over a 2kHz or 500Hz bandwidth, (the frequencies for each mode/bandwidth are hard coded in the software which is causing some annoyance amongst some users. ROS has three main speeds, 16 baud, 8 baud and 4 baud. There are some special modes, such as 7bd/100Hz for 136 and 502kHz (and 80m for some reason), plus an ‘EME’ mode for use on 2m and some other bands, for weak signal work as it has, in theory at least, the capability to decode signals that have a Signal to Noise Ratio (SNR) of -35dB, which is even lower than  WSPR. There are, however, questions as to the legality of using the mode on HF in North America, as spread spectrum is not allowed below 222MHz and the authorities are still undecided if ROS is SS or not.

This will all be hammered out as the mode grows. It will either become widely used or, as is sometimes the case, just disappear through lack of interest. Only time will tell on that. One thing that has come to light is that ROS has just been accepted into the ADIF standard (Amateur Data Interchange Format), which is the common ‘language’ that is used for exporting and importing log data. Also (the electronic QSL exchange centre) has updated it’s system to accept ROS QSO’s.

ROS v5

Click on pic below to hear the sound of 16 tone, 500Hz ROS

ROS 500Hz-4
ROS 16
The above pics are taken from the ROS program, which uses a monochrome waterfall. As most software uses a color waterfall, I have included a screenshot of a ROS signal (in this case the same as above, 16 tones / 2000Hz) as viewed on the HRD waterfall.
ROS 16-2

To download the software and users guide: - it is worth checking there at least weekly as new versions are being released frequently in response to users requests for features etc. (the latest version is v 7.0.8). Here are the latest frequencies, as of May 2012. Note: these are considerably different to the previous version that appeared on this page.



136 kHz


500 kHz


1840 kHz


3583 kHz


3585 kHz


3587 kHz


3589 kHz


5367 kHz


7040 kHz


7044 kHz


7046 kHz


7048 kHz


10132 kHz


10134 kHz


14101 kHz


14103 kHz


14116 kHz


14118 kHz


18107 kHz


18111 kHz


21110 kHz


21115 kHz


24916 kHz


24926 kHz


28185 kHz


28295 kHz


50245 kHz


144160 kHz


144980 kHz


432097 kHz


There is a buzz of excitement as Joe Taylor, K1JT, has now released the first version of WSJT 9 - which can be downloaded from: There are some new modes in this version although I have not had time to investigate them as work is very busy at the moment and will be for another few weeks. There was a brief beta test version of WSJT, version 8, that investigated a host of new modes and this research and it’s findings have gone into producing the public release of version 9. I will provide more information on these modes as it becomes available (screenshots and mp3’s etc). It’s a busy time in digimodes, there always seems to be a new mode or refinement of an existing mode being released. ROS is still finding it’s feet and is under constant development - it still has its critics, but that is true of most modes but it does seem to be getting quite popular, although I doubt if it will ever be as widely used as, say, PSK31.


RSID is a method of identifying certain digimode signals. RSID stands for “Reed Soloman IDentifier”. The way it works is that the station who is transmitting can, in certain software, enable RSID. When enabled, RSID sends out a numeric code in the form of an MFSK signal which is identified by the receiving software (if it is capable of RSID) and sends alerts to the user and advises of the mode used. This is particularly useful with the lesser used/recognised modes, however it can be rather tedious to have an alert every time someone starts transmitting in, say PSK31 or RTTY as these are extremely common modes and you can find yourself inundated with alerts. In some software RSID can be configured to be active for certain modes only. In DM780, a box appears on the desktop alerting the user to a transmission and gives the frequency and mode (such as Olivia 23/1000 on 1500Hz) and you can tune to that transmission by clicking on the alert box which will change the mode and frequency of your radio (providing you have computer/software control set up).


Video ID is different to RSID in that it can be seen by anyone using software with a waterfall display. Again, video ID is enabled in the transmitting software and it is not supported by every software. If you are watching a waterfall trace, you may, at the end of the transmission, see some text or even a crude picture in the actual waterfall - this is video ID and confuses many people who have not seen it before.

waterfall pic sstv 2
psk125 with 73 pic


Below are some less common modes, together with sound files. This list is certainly not exhaustive (not by a long, long way!) but it might just give you an idea of what that strange noise was that you heard when tuning around on SW. New data modes are emerging all the time and it is difficult to keep up with them. I usually follow the development of new modes that I think might interest me - some of these modes become popular, some much less so.

Unfortunately I do not have waterfall traces for these signals yet, but I will endeavor to track some of these signals down and capture them (that’s why they call it ‘hunting’ :)

For technical details of the modes below, and others, visit: (where some of the following information has been verified/sourced.)

SITOR: SITOR  is a commercial teletype mode it means SImplex Teletype Over Radio) used for sending text messages between stations, SITOR may be run in interactive (ARQ - Automatic  Repeat reQuest) mode, which is known as SITOR-A (also called AMTOR). When SITOR is run in broadcast (FEC - Forward Error Correction) mode, it is known as SITOR-B (or NAVTEX). The mode uses special error correction techniques. There are many ARQ and TOR modes to be found on the HF bands, SWEDISH ARQ, G-TOR and CLOVER are just some. If you start investigating, you will be surprised by just how many commercial digital modes are in use.

CHIP: This mode was created by IZ8BLY back in 2005. Chip is a PSK mode which uses "Spread Spectrum" modulation and comes in 2 variants, Chip64 and Chip128. Chip has a bandwidth of almost 600Hz, but is an extremely robust mode and has a good throughput speed.

ALE: (Automatic Link Establishment), is now finding more use in amateur circles, thanks to the efforts of the writers of some of the multimode decoders, such as MultiPSK. ALE, when running correctly, can initiate and establish connections between two stations without human intervention (hence the ‘Automatic’ part.)

PAX, PAX2: PAX is another MFSK mode which is derived from Olivia. PAX2 is the same as PAX but runs at a higher baud rate (62.5bd for PAX and 125bd for PAX2), therefore PAX2 is twice as fast as PAX but requires a better signal to noise ratio. The following frequencies are used for PAX/2: 3.590, 7.042, 10.148 and  14.075MHz .

STANAG: Used by the military, comes in many different variations. Pretty much all Stanag traffic is encrypted. STANAG 4285 is the NATO standard for HF communication. It consists of several sub modes (75-2400 bps) and two different interleaving options (short and long). The receiver should be in USB mode and provide flat frequency response from 600 Hz to 3000 Hz. Another Stanag mode is 5066, which includes mode identification in it’s data and can therefore be detected correctly by multimode auto detectors that are built into some software.

HFDL: HFDL stands for High-Frequency Data Link. It is used on the HF bands and is a comprehensive, global, air-ground, communications system. (It also uses VHF and satellite). ACARS (Aircraft Communications Addressing and Reporting System) is part of  this system and with the appropriate software, aircraft routes and progress can be seen on a pc screen. HFDL is a single-tone, phase-shift keyed, text-based, error-checking mode, with a base band audio carrier frequency of 1440 Hz. It is tuned in USB, and the 1440 Hz center is critical for decoding. (Thanks to Monitoring Times blog for the info on this)

NAVTEX: NAVTEX is a world-wide system which transmits navigational and meteorological warnings, and urgent information through coastal stations. Transmissions are on 490kHz (National NAVTEX, broadcasts in local languages) or 518kHz (International NAVTEX, in English), in FEC/SITOR-B mode with special coding. The receiver should be in USB on 489 or 517kHz. Transmissions are at fixed times, the schedules for which can be found on the internet ( is one source).

navtex 517-2

NAVTEX transmission received on 518kHz on 9th October 09, the text shows the co-ordinates of two special buoys.

SYNOP: Synop is used by ships, and shore based weather stations to report prevailing conditions and forecasts. It is RTTY that has specially coded messages which allow the display of ships and weather buoys/stations and shows weather forecasts and conditions, when used in conjunction with the appropriate software. There is a SYNOP station on 10.101MHz in Germany, it runs at 50baud, with 425Hz shift and is reversed/inverted (when received on USB).

COQUELET: Screenshots and audio are being prepared. This mode is not used a great deal on HF but can sometimes be heard on 18.181MHz where there is an Algerian station (possibly a diplomatic service) that uses Coquelet and broadcasts some non encrypted text in French.

coqulet 8 on 18181-3

coqulet 8 on 18181-4


Using DM780 (part of the excellent and free Ham Radio Deluxe radio control, logbook and decoder package, by Simon Brown HB9DRV) and PSK Reporter (By Phil Gladstone) I am able to set my radio up on any one of the designated PSK31 frequencies and let it monitor for as long as I wish. Each time a callsign is decoded, it is logged, along with its WWlocator. These locators are shown on the PSK reporter page as pins in a scalable map (the map can be displayed as a map, a satellite image or a hybrid of both). Occasionally a callsign is recorded that is not correct (might be a fragmented call or a call that has been corrupted due to noise or QRM). These are surprisingly rare considering the amount of traffic that the program decodes and shows just how good the programming is. It is fascinating to see the map at the end of a monitoring session, and seeing what the chosen band has had to offer that day. I have been doing this for some months now and am noticing interesting propagation trends that tie in with established theory. Below are some screenshots from the DM780 program taken at various times and dates that  illustrate the diversity of stations on the air. Some callsigns appear most days, others of course are only heard once.

Click on each map for a bigger and more detailed picture, then use your browser 'back' button to return here.


L-R:  PSK31 stns on 20m (23 Aug 09); PSK31 stns on 20m (25 Sep 09); DXCC count on 20m PSK31 (2 weeks monitoring) 

4_192x1125_194x1186 oct 09 20m_341x129

USA on 20m PSK31 (25 Sep 09); DXCC count on 20m PSK31 (1 month monitoring); Screenshot of 20m taken on 6 Oct 2009 showing stations heard on all 6 continents (for ‘All Continents’ awards, Antarctica is not counted) on 20m PSK31. Although I have shown stations from all continents, they were not the first heard from the particular continent. I have chosen the stations listed below because they have the shortest time frame from first to last.

Elapsed time between hearing the first continent and the last was a mere 53 minutes! just think how quick it could have been done if I was using good antennas!























It is not unusual for me to hear over 90 countries on PSK31 during the course of a week (last week was 96 for instance), certainly that has been the case over the spring/summer, with 50-60 countries per day being about average. - and that is at the sunspot MINIMA! I would think that in a few years time I should be hearing over 100 countries in a week without a problem. Bearing in mind I am using a very low antenna, it just goes to show that even when you think the bands are quiet and there is no propagation - most of the time you would be wrong! 20m has been open from early morning to late night, and probably 24 hours but I have not monitored in the small hours of the early morning - yet!


Below are some shots taken from the ‘Spectrum Laboratory’ program (freeware). Each shot covers about 1 hour of elapsed time and shows the amount of activity on the given sub band during that time. Click on each thumbnail for a full size image, together with explanatory text.



JT65-HF (Original version)

JT65-HF is no longer being developed by the author, but the project is far from dead, with at least 2 others producing different versions of the software (these are being called ‘JT65HF Comfort’). The way the progams look and feel compared to the original is pretty similar, but each has a set of features different to the other. I will continue to host the original software and will provide links for the other ‘forked’ versions on the digital modes page.

I am pleased to offer this site as a mirror download site for the original JT65-HF software from Joe Large, W4CQZ.

Please click on the picture to download the setup EXE file for JT65-HF v1.09.3 (the latest/last version).


If you wish to download the previous version (1.07 - zip file, with instal instructions) click HERE

For more information on JT65, see my Digital Modes page


Since the demise of the ‘Shortwave Log’ Logging and control software by Bob Sillett, there has been nowhere that users can download the setup file. I have decided to host the setup file on this site, but it has to be remembered that some of the external databases will not be available or will have changed format during the time since the last edition was released.

Also bear in mind that you will require various other programs to be loaded onto your computer (from Microsoft and others) in order for SWLog to function. I offer no warranty or backup for this program, I am just acting as a host. If at anytime the author of SWLog contacts me and wishes me to remove the program from my site I shall, of course, comply with his wishes.

You may download the SWLog setup file (build 4460) by clicking HERE. I have scanned this file with various anti-malware and anti-virus programs and it shows as being clean. However, please ensure that you scan it with your preferred software before running it.


**If you have problems playing back the MP3 files  please read this, it might help:-  I found that Windows media player would not play one of my mp3’s but Quicktime would. Having done some research I see it is a common problem with WMP.  Use the free Apple Quicktime player or similar - also consider installing a codec pack (again many can be downloaded and installed for free) such as the AC3 codec pack and that will (or should allow you to play any, or most,  mp3’s you come across as well as other formats)**

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