--- KV9U <[EMAIL PROTECTED]> wrote: > Walt, > > Maybe someone can clear this up, but what is the > difference between the > differential modes such as DBPSK, DQPSK, 8DPSK, and > 16DPSK such as used > with Pactor 2 and modes such as 8QPSK, 16QPSK?
Even when theory says that differential modes have a worse BER, seemingly they work better on ionospheric paths, as with a moving ionosphere, is difficult to maintain an absolute phase reference. > With the former, it is my understanding that with a > single tone, the > binary form (DBPSK) gives you one bit/second, DQPSK > two, 8DPSK three and > 16DPSK four. Still holds true... > With the previous discussions on baud rate for the > STANAG and MIL > modems, can we still say that HF should use baud > rates below 45? Depending on multipath, which is worse on lower frequencies. > The claim is that these modems appear to be able to > use extremely high > baud rates, well above even 300 baud on HF and still > work well under > difficult conditions. The game is using many slow channels in parallel. Already in 1991 there was a 41 parallel tone modem being tested in transatlantic paths...it was capable of running 4800 bit per second and sometimes, up to 9600. > In fact, the ALE folks believe that amateur radio > is being held back on HF because we can not transmit > in excess of 300 baud on most HF frequencies. Signalling rate....the speed at which every tone is wiggled. Actually, the ionosphere imposes a much lower rate for succesful transmission on the lower frequencies. > Even Pactor does not exceed 200 baud and that is > only under the best of conditions and even at 100 > baud, the claim by Dr. Rink was that "The > short term time jitter has a magnitude of up to 5 > msec. Larger time smearing can only be observed > under very special conditions of the > ionosphere. A baud rate of 100 symbols per second > has proven to be low enough for almost all possible > propagation conditions, especially if > powerful error control coding is applied. > > Is there anyone here who can further explain this? Once again....Pactor can adaptively switch from 100 to 200 baud and back...be either Pactor I, II or III. Additionally, it can adaptively switch in and out constellation complexity and quantity of tones. Using compression, FEC and the whole boxful of coding tricks, it can go up to 5200 bits per second. I have seen it on Pactor III ocassionally running up to 3600 bps on 40 meters, and more often, 2800 and 1400 bps. 73 de Jose, CO2JA __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com Need a Digital mode QSO? Connect to Telnet://cluster.dynalias.org Other areas of interest: The MixW Reflector : http://groups.yahoo.com/group/themixwgroup/ DigiPol: http://groups.yahoo.com/group/Digipol (band plan policy discussion) Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) <*> To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
