From my perspective, perhaps some of the reasons are: - Some digital programs only support a few modes, but typically they are all going to support PSK31 and RTTY
- As new modes are developed, they are invariably going to be compared to the existing leaders and need to have some compelling new advantages. - At first many of us are curious and want to try out the mode to see how it performs (or not). But after a few months, it may be found to have certain undesirable traits compared to the baseline modes (even though it may also have some desirable traits). - Most new modes do not seem to have significant improvements over existing modes if you take the tradeoffs into consideration. Does the new mode have adequate keyboard speed like PSK31? Is it an efficient, narrow mode, or a wide bandwidth mode that may not have a large advantage? Is it easy to tune in and tolerant of not having to be exactly on frequency? Does it have much latency (the time it takes to quit sending the data)? Looking at specific modes: - RTTY for contesting due to having low latency and ability to have the quick turn around that contesters require and adequate speed of 60 wpm with 45 baud RTTY. Other modes, including PSK, do not do well in that environment - PSK31 for most chats. Speed about 40 wpm, can handle more ISI than RTTY, very sensitive, very narrow mode. - Olivia is relatively slow and in order to have the more robust protocols is relatively wide with the 8 tone/1000 Hz mode which has a speed just under 60 wpm so is incredibly wide compared to PSK31 but with better throughput. Many of the Olivia modes are under 30 wpm and even under 20 wpm! Can handle polar flutter. - MT-63 has good speed, but not very sensitive and has the wide bandwidth, hard to tune with weak signals, but can handle severe interference and ISI with a fair to good signal. Has very significant latency after the data is entered until it is all sent. Typically over 6 seconds delay, but very good at handling selective fading. - MFSK16 has very good weak signal capability, narrow bandwidth, slow baud rate very good tolerance to . Difficult to tune in and can not tolerate much frequency error. - DominoEX seemed like a good mode, and excels at handling ISI with slower speeds as needed, easy to tune in, good speed for the baud rate with the 18 tone IFK, narrow bandwidth, but surprisingly can be affected by the ionosphere quite severely. A real eye opener is the experience of Rein, PA0R, when he attempted to use other protocols than PSK for PSKmail. I think he was surprised how poorly the MFSK/IFK modes worked compared to faster baud rate PSK. In fact, PSK125 seems to work very well with an ARQ mode. - CHIP modes were mostly experimental and did not perform well at least at the 300 baud rate, not very sensitive, prone to errors, modest speed considering the baud rate. - THROB and THROBX, with the very slow speeds can go deeper into the noise with an multitone FSKsignal but at the speeds competitive with PSK31, perhaps not that much of an improvement in performance. Consider that after all these years, with their third change in modems, SCS designed the Pactor 3 protocol to: - keep the symbol rate at 100 baud instead of switching between 200 baud as done in P2 - keep the constellation simpler at only 2PSK and 4PSK, not even 8PSK - avoid ASK modes which they found years ago did not work well on HF - use multiple tones that can be dropped off when conditions get rough in order to have wider spacing 73, Rick, KV9U - Andrew O'Brien wrote: > What happened? It seemed that Olivia was poised to become the third > most popular digital data mode (after PSK and RTTY). Now OLivia and > also DominoEX are way down in use. I think that PSK and RTTY are > still number 1 and 2, JT65A appears to be number 3 followed by MFSK16 > and Hell. Heck, I think you will here more ALE and PSK125 than you > will hear Olivia these days. > > Andy K3UK > www.obriensweb.com > > >
