Having worked with PCTEL using a soft modem for 56K baud for handhelds, I
noticed that it took like 40-60 seconds for the line condition to be
characterized (echo cancellation and phase shift) before any data could be
transmitted. So think about this, can the transmission techniques in the
software for AX.25 (or other format) support half-duplex with a 50 second
turnaround? Well at least at 1200 baud the turn around time (sync up to
the sound) is in the few hundred millisecond range.
It would be interesting to get a softmodem design to support Higher baud
rates
from a manufacturer supporting Linux. But the softmodem software would not
be
free. I am sure there a few hurdles to over come. Wonder if using a
protocol
like Z-modem (windowing technique versus X-modem which ACKs each single
packet) and full dulex (like a repeater with separate TX & RX frequencies,
You could have a 56K link in one direction. With a 300 or 1200 baud link
in the other direction just reporting which packets were in error and which
were received correctly.
Then maybe you could get the high forward transfer speed. Someone has
probably
already thought this through and decided to many technical difficulties for
it
to be worth doing.
Fred Finster WB7ODY
e-mail: [EMAIL PROTECTED] Web Site
http://www.necel.com/windowsce
Tech Staff Engineer (408) 588-5726 FAX (408) 588-5464
NEC Electronics Windows CE Architecture Labs
2880 Scott Blvd. M/S SC2202
PO BOX 58062
Santa Clara CA 95052-8062
personal WEB with 6Meter Regen Rig http://home.earthlink.net/~fred_finster
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]]On Behalf Of Thomas Sailer
> Sent: Wednesday, October 13, 1999 4:01 AM
> To: Arno Verhoeven
> Cc: linux-hams
> Subject: Re: re-program 56k telephone modem for packet radio use?
>
>
> Arno Verhoeven wrote:
>
> > Wouldn't it be possible to use one of these modems and re-program it for
> > use with packet radio?
>
> Good luck trying to get docs from the manufacturer of the chipset.
>
> Tom
>
