If we really could run voice on 300 Hz BW, I would support using it in a narrow digital area since I think that it is good practice to provide protection for narrow modes against the wide modes. Ironically, that is not what is currently in the FCC rules. We have very wide BW modes, running in the text digital areas of the HF bands, but you can not run narrow modes in the wide portions of the bands (the image/voice portions).
I honestly think that much of this HF DV stuff is pie in the sky. It might be possible that there could be a breakthrough in digital technology which would turn things upside down but then again is that realistically going to happen? The restricted BW voice modes are pretty much following theory and the quality suffers terribly in terms of comprehension. But let's say a miracle occurs and you could get greatly improved quality with a narrow bandwidth. If that happened, we would see a migration to the narrower voice modes which will free up a lot of bandwidth. But I don't think this will happen as DV will be difficult, if not impossible to operate with other signals in the passband. This may work with military/commercial channels and high power, but it just does not have the technological edge that SSB has for weak signal, high QRM, shared frequencies, that are so typical on the HF ham bands. As you point out, there are hams who read the text back with a "voice" and it has been around for many years. If you recall, not long ago (year or so?) there was a QST article about a ham sending PSK31 via a speech to text conversion so that is also being done, at least on a limited basis. Whenever new modes come along that really have a compelling value, they are eventually adopted when the cost/benefit ratio makes it possible to do so. Either for widespread use if they stand the test of time, or sometimes for niche purposes as we are seeing with some of the text digital modes. I rarely get involved in contesting, but it appears that RTTY works better for fast exchanges. At least it may be perceived that way. I have tried PSK31 for casual quick contacts such as Field Day and found it impractical for me to work many stations compared to voice. I have not tried PSK63, (other than casual tests) but hope to use this for a very different purpose when the MS Windows version is made available for the emergency communication program that is currently being used on Linux. Are you personally involved in that project as you were with the Linux version? 73, Rick, KV9U kh6ty wrote: > Rick, I prefaced my comment with " It is my belief that if "voice" of the > same bandwidth were allowed everwhere > "data" is allowed, the data segments of the bands would be overrun with > phone stations using DV." > > Perhaps it is not clear what I meant. For example, if someone comes up with > a DV of 300 hz bandwidth, it will quickly be widely used anywhere 300 hz > bandwidth signals are allowed, and the crush of phone users will leave > little space for modes like MFSK16 of the same bandwidth to operate, simply > because there will be so many people wanting to use phone instead of another > digital mode, like MFSK16, but that is just my personal belief. > > If there were a DV mode the same width as PSK31, then the same would prove > true, except that there are more spaces to use PSK31, because of its narrow > bandwidth, than there are digital operators looking for space (right now, > but changing). In fact there already is a sort of narrowband "DV" in my > DigiTalk program for the blind, which "speaks" the PSK31 text (at 50 wpm > text-to-speech), but, because going the other way (speech-to-text), still > has a 5% translation error rate at best, "speaking" must still be done by > typing, and that is a deterrent to many who might use PSK31 if they could > just speak into a mike and have errorless text go out over the air. > > As you point out, some sort of planned segregation is going to be inevitable > on shared bands. With phone and CW, there was a common language for > everyone, and sharing was possible by QRL or other Q signals on CW or the > equivalent on phone, but that sharing technique is useless when one mode > does not hear or understand another. We have yet to experience what it will > be like if everyone uses DV, there is not enough space to hold everyone, and > someone accidentally starts up on your frequency because propagation was > such he thought it was clear and did not happen to choose an alternate clear > frequency he could QSY to if he could just understand a request to do so. > > I believe the thing that makes it possible for PSK31 to have a space, for > example, is only that there is no true 31.25 Hz-wide phone mode. Of course, > the more narrow the mode, the more stations that will fit in any given slice > of spectrum, so it is advantageous to have the most narrow modes possible so > there is room for as many stations as possible. At some point, there will be > plenty of space, depending upon the demand, even if everyone used a voice > mode that is only 31.25 Hz wide. For example, if every RTTY contester only > used PSK63, there would probably be more than enough space so that during > contests, RTTY stations would not have to spread out so much. > > There was a psychological experiment some years ago in which scientists set > up two cages of rats, one overcrowded and one just at capacity. The rats in > the overcrowded cage ate each other until they were no longer overcrowded. > > Skip KH6TY > > > > >
