The reason that the Winlink2000 owners do not want busy frequency detect is that they invented a particularly effective version of such a mode and found that they would have extreme difficulty finding a wide enough bandwidth to operate. The signal detection circuit would be reset to standby until a clear frequency was available.
A human operator is always going to be on one side of the circuit for "semi-automatic operation," but it does not insure that the hidden transmitter effect would not occur since the human operator would not be able to hear what the robot station can hear. In the past, there were complaints about the packet forwarding stations. These stations were mostly "fully automatic," by which we mean they had robots at both ends with no human intervention. I believe that this is also true of other automatic forwarding systems, such as Aplink and Winlink, both of which have been discontinued for many years. Most HF packet BBS auto store and forward systems have also been discontinued as well. The Winlink 2000 system went primarily to using the internet and does not currently have the capability to operate without internet, except in a special case where a local group gets permission to set up a local hubbing PMBO server. Then you can at least communicate between stations that can reach the PMBO, but you can not forward to other servers. My understanding is that they are working on changes to their system to eventually allow forwarding to other servers via RF, instead of the current internet only system. While there is currently no sound card mode that can do exactly what P2 and P3 can do, the SCAMP mode proved that you could use a very basic waveform, e.g, RDFT, not necessarily optimized for HF use, and get it to send messages amazingly fast. It really was an enormous breakthrough because it proved it could be done. But unlike P2 and P3, it had no mechanism for weaker signals and the programmer simply gave up on further development and then did not publish the sourcecode either. I am probably in the minority who believe that this has been a major loss to the amateur community, but imagine if this was a programmer who was not working with the Winlink2000 owners and was interested in furthering messaging and willing to work with others to develop a serious ham to ham communications mode as well as provide internet e-mail capability as needed by setting up an ad hoc server anyplace that internet service could be obtained. At this time the only system that can do this is PSKmail, although at a very slow speed and may or may not be practical, particularly due to running under Linux at this time. When I look at the computer simulations done by Rick, KN6KB, the SCAMP inventor (using an average of ionospheric conditions) he shows: At the best conditions of +10 dB, P3 at 225 cps, SCAMP 97 cps, P2 50 cps, P1 20 cps, MT-63 20 cps At +5 dB -- P3 ~ 150 cps, P2 ~ 40 cps, P1 20 cps, MT-63 20 cps At zero dB -- P3 ~ 66 cps, P2 ~ 25 cps, P1 20 cps, MT-63 20 cps At -5 dB -- P3, P2, at or below 20 cps cps = characters per second As you can see, P1 is about the same as MT-63 (20cps at the wider 2000 Hz mode). He claims that his simulation showed that MT-63 and PSK31 failed at just below zero dB, but I don't know how he could possibly come to such a conclusion. The point of all this is that a sound card mode can definitely be competitive in speed with P2, although much wider, and still be reasonably competitive with P3. And it is not difficult to imagine that a new mode, that is similar to P3 would be very practical to do as a sound card mode. The basic building block is a multi tone PSK OFDM kind of mode that drops off tones if it needs to be more robust, and uses some basic control signals between the stations to determine how many tones and what modulation constellation should be used. The SCS development of P3 suggests that ONLY DBPSK and DQPSK should be used and the baud rate kept at or below 100 baud. This gives you ability to withstand polar flutter better than slower baud rates, and yet the multipath may be able to be corrected by using a coded modulation. Maybe improved Turbo codes instead of Viterbi? The only other way would be to go to a single tone modem, such as the military/governments tend to use with an extreme baud rate with compensating codes. I think a key issue here is to come up with a compromise baud rate and not change it. P3 could have had higher rates like P2, but they chose not to do this. I think that is due to their finding that switching baud rates can be counterproductive. G-Tor from Kantronics could do 100, 200, or 300 baud and I have heard would spend way too much time figuring out which baud rate to use. But as you say, for keyboard use, the sound card modes work well. 73, Rick, KV9U Demetre SV1UY wrote: > First off PACTOR 3 supports DCD control so it can listen before it > transmits. Now maybe the Winlink people have a good reason to have > their automatic MBOS not support the DCD control, but the human > operator that calls an automatic MBO can listen to the frequency and > make sure noone else is using it before he transmits. Also this will > make sure that if someone's life is in danger they can reach the > autoanswering MBO no matter what. It is not the end of the world if in > a rare occassion someone's QSO is ruined if it is for a good cause. > Now I can hear you saying that people can abuse this. Well in this > case you canreport them to FCC. I think that this is called > semi-automatic operation. > In the past when we had PACKET FORWARDING taking place, non stop, day > and night, noone was complaining. Why was it OK then and it is not OK now? > What about all the contesters that transmit wherever they want without > even asking if the frequency is on use? Do they own the frequency? > PACTOR MBOs and maybe ALE systems are just lurking there and if the > frequency is clear and someone calls them they respond. The way I use > WINLINK PACTOR MBOs is to first listen for a while, make sure the > frequency is not busy and the call. If the frequency is busy I QSY and > try to contact another MBO, the same way as before. If all the > frequencies that PACTOR MBOs are available are busy then I wait. It is > not the end of the world if I do not get through to them straight > away. But if my life or someone else's life is in danger, then I will > use the most available power and QRM anyone who is in the same > frequency. I think this is fair. > > As for your last comment, I also wish there was a soundcard mode or a > system of combined soundcard modes that can do what PACTOR 3 can do. > There isn't any though. There isn't any soundcard mode that can do > even what PACTOR 2 can do. It is either impossible to develop as a > soundcard mode (which is the most likely to be true), or programmers > are too lazy to do it (which I don't believe so much), or programmers > want to make some money if they ever find the time to develop such a > beast. SCAMP is a perfect example of what cannot happen on HF. It was > good only when there was no noise. It lost the link at the slightest > noise. I followed this experiment all the way until it was abandoned, > and I don't believe that WINLINK people are paid agents of SCS 'cause > this is a story that has been mentioned as well by ignorant people in > many mailing lists. I don't think you do either. > > In any case I am back to PACTOR 3 any day. I am not wasting my time > with PSK in a soundcard because I could be wishing and waiting until > 2050 or later, if I'm still alive then! hi hi hi!!! I still like PSK31 > for a QSO because this is way to make DX though but not for > filetransfers, e-mail etc over HF channels. > > And remember PACTOR 3 is not WINLINK. Winlink uses PACTOR 3 (it is not > the only system that uses it) and if some think that they do not use > it correctly, well it is a matter of opinion. > > Life is too short man, enjoy it while you can. > > 73 de Demetre SV1UY > > > > > Announce your digital presence via our Interactive Sked Page at > http://www.obriensweb.com/drsked/drsked.php > > Yahoo! Groups Links > > > > > > >
