--- John Becker <[EMAIL PROTECTED]> wrote: > Your are right Bill but I don't see any software > that will keep up with that TNC in Amtor or Pactor > ARQ mode as yet. And both modes are still very alive > and well. > > John, W0JAB
Well, some 8 years ago I built a quite complex homebrew modem with opamps and LSI TTL that was useful for RTTY/AMTOR/PACTOR(I)...and packet....it was my version of the AN93 modem...revisited and built with MY junk box parts. Worked in fairly decent way...good ears...low pass (-3 dB @ 150 Hz) filtering after the demodulators was decisive for the performance under noise/qrm. Borrowed a couple of ideas from a KAM schematic... Using MSDOS and TERMAN93 it worked quite right for RTTY, AMTOR and PACTOR I. RTTY was easy, but PACTOR required that the video dot clock, 14.318180 MHz on my old 386 was within a few ppm of the correct frequency. I had to do some surgery on the motherboard to add a trimmer and pull it a bit higher....it was originally on 14.312 MHz...allowed me to be master but never slave in the link ....correcting the xtal frequency allowed it. On pactor, it only negotiated going from 200 baud to 100, but 100 to 200 hat to be done manually. For packet (not originally planned...it was one of those summer evenings what if...?? endeavours) I tried it with bpqax25 ....and it worked better than my KPC-2 on 40 meters, even using 170 Hz shift. I blame it on the better baseband filtering of my homebrew modem...it did cope better with noise on 40 meters than the AM7910, whose baseband was wide open for 1200 baud packet... I got my PTC-II for Christmas 1998.....I never put my homebrew modem in a case...it lies on the bottom of some drawer...now the PTC-II handles the AMTOR and PACTOR stuff, and software does the rest of the newer modes... 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/ <*> 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/
