Considering the subset of protocols on Rick's list (below) for which soundcard-based applications are available, PSK31 comes out on top. For keyboard-to-keyboard operations, however, I don't believe that absolute spectrum efficiency explains PSK31's stickiness. I suggest that the follow three factors are what's responsible for its stickiness:
1. the number of QSOs that fit within 3 KHz A typical 3 KHz transceiver bandpass enables panoramic soundcard software to simultaneously display up to 50 QSOs or calls (though 25 is a more practical capacity). This is large enough that operators often park their transceiver on a single frequency (e.g. 14070) and use their software to find ragchew partner, needed DX station, or friend with whom a sked has been arranged. As discussed in an earlier thread, most soundcard software can then QSY the transceiver to place the desired signal at an audio offset optimal for the transmitter's bandpass and receiver's filters. 2. speed At 40 WPM, PSK31 is "fast enough" for most hams. 3. resiliency Though far from perfect, PSK31 does a reasonable job under adverse band conditions. While many DXers still prefer RTTY, more and more RTTY DXers maintain a PSK31 capability to work DX stations active in this mode (PSK QSOs "count" as RTTY in ARRL DXCC awards). The successful use of PSK31 on topband and 80m is another indicator; these bands are always blessed with QRM and/or QRN. You might think that the younger generation of touch-typing hams would find PSK31 "too slow". PSK63 provides double the speed, but a. many keyboard-to-keyboard ops who tried PSK63 reported discomfort with their abiity to keep up when transmitting (other than when sending and receiving long brag tapes) b. PSK63 would have cut the 3 KHz "capacity" from 25 to 12 QSOs Years ago, several of us ably led by Skip KH6TY tried to establish PSK63 as an upgrade from PSK31 and a replacement for RTTY. No sale -- there just wasn't enough incremental value to trigger a migration. Several folks on the DXLab reflector have asked for PSK125 support, saying that this mode is on the upswing in Europe. MultiPSK, which interoperates well with DXLab, supports PSK125; it will be interesting to see how the "much faster, but less robust and fewer QSOs in 3 KHz" tradeoff works out. For keyboard-to-keyboard operations, speed beyond 50 wpm is of questionable value and error-free transmission is not an absolute requirement because "manual ARQ" is available ("sri OM missed ur name pse rpt ur name"). In contrast, message-passing systems require error- free transmission. For them, higher speed means increased message capacity, and panoramic reception is of little value, so wider bandwidths do not impede adoption. In other words, they are an entirely different kettle of fish -- both in terms of the characteristics valued by their users, and the modulation and protocol techniques appropriate to their implementation. Comparing keyboard-to-keyboard and message-passing protocols on the same axes makes no sense. The point of this post is not "PSK31 is the best keyboard-to-keyboard protocol; let's stop trying to invent something better". Rather, its to identify the characteristics that have enabled PSK31 to remain so dominant despite the subsequent 7-year explosion of new soundcard modes triggered by its appearance. The protocol designer looking to develop a more attractive alternative to PSK31 for keyboard-to- keyboard operations should consider focusing on significantly increasing QSO capacity within a 3 KHz transceiver bandspread without seriously compromising either speed or resiliency. PSK31 first appeared at the rather stunted peak of the last sunspot cycle; since then, its adoption curve has looked like the inverse of the solar flux curve. As we enter the next solar cycle and propagation improves, 25 QSOs per band will likely prove insufficient; thus a more dense keyboard-to-keyboard mode could displace PSK31 if its other important characteristics aren't degraded. As for the other kettle of fish, I will leave their future to those interested in message passing systems. After all the discourse here, I trust that they will see the light and provide means to ensure that such systems never transmit on busy frequencies. 73, Dave, AA6YQ --- In digitalradio@yahoogroups.com, Rick <[EMAIL PROTECTED]> wrote: > > Consider that voice SSB requires over 2000 Hz for reasonable quality and > 2700 Hz would be better. Speaking on the air may be about 120 wpm. That > figures out to around ~ 20 Hz per wpm, give or take some. For passing > traffic it would be much slower though with more Hz per wpm. > > PSK31 is about the narrowest mode available to communicate at that > speed. Even CW may be around the same bandwidth (~ 60 Hz). This allows > enormous numbers of hams to set their dial frequency at one point and > must move their cursor to read out or even contact or call other hams. > > PSK31 can be sent at an average speed of around 40 wpm in that 60 Hz > bandwidth, or 1.5 Hz per wpm. If you only look at throughput per > bandwidth you find that if you need high speed, robustness, and > accuracy, nothing can touch Pactor 2 and 3. If you need keyboard speed, > then it likely be a different story. > > Scaling different modes, under moderately good conditions and using > Patrick's Multipsk information and some averages with ARQ modes from > KN6KB's RF Footprint Powerpoint: > > Mode bandwidth (Hz) / speed (wpm) = Hz/wpm > > Olivia 32/1000 - 1000 / 24 = 42 > > ALE MIL-STD-188-141A - 2000 / 76 = 26 > > Olivia 16/500 - 500 / 20 = 25 > > Olivia 8/1000 1000 / 59 = 17 > > FAE = 2000 / 150 = 13 > > MT63 1000 / 100 = 10 > > 45 Bd RTTY 600 / 60 = 10 (some will consider this narrower and with a > better score) > > MFSK16 - 316 / 42 = 7.5 > > Pactor 1 200 / 600/200 = 3 > > ThrobX - 94/40 = 2.3 > > DominoEX/11 194 / 77 = 2.5 > > PSK31 60 / 40 = 1.5 > > Pactor 2 700 / 500 = 1.4 > > Pactor 3 2400 / 2225 = 1 > > If you adjust some of the numbers for conditions where the S/N is well > below zero dB, then I think it would change things a bit. Some of these > numbers are guesstimates so if anyone has other suggested numbers, it > might be interesting. The main thing is to look at the relative > comparison. But we need to keep things in perspective, since all things > are not equal and a wide footprint mode for keyboarding would be > difficult to justify unless it had special abilities to handle difficult > conditions as some of these modes have. I could do another SWAG on this > with say, -5 or -10 S/N. > > 73, > > Rick, KV9U >