Linux-Hams archive - December 1999: Re: linux soundmodem over 9600 baud ?

Re: linux soundmodem over 9600 baud ?

Robin Gilks (lwtp.csrugup@mail.dy.fi)
Wed, 1 Dec 1999 08:46:17 +0000

On Wed, 01 Dec 1999, you wrote:
> Kantronics KPC-2400 used QAM and was regularly used to
> modulate FM transmitters. I don't even know of anyone ever
> successfully using it through a linear transmitter. I remember
> it well as it was the last modem I did for AEA for the DSP-x232
> box. It is V.26B tones and a royal pain in the butt.
>
> Bob
>

Now thats interesting....

I've been using ex British Telecom 4th generation modems type 4241x for a
couple of years on a 70MHz link at 2400bps. These are 4 wire modems (leased
line) that use V26B tones with V27ter scrambling, dibit encoding the 2k4 at
1200baud. Using a variety of phase and FM modulated radios, they have all worked
extremely well (and within a 10KHz channel) - very short training time and the
interface is a simple VOX switch operated by the TX audio keyed by running them
in half duplex using RTS as the turnround signal.

The interface is either an SCC card, a home brew KISS only TNC or a modded
version of the DOS Baycom TSR ax25.com which outputs a bit rate TX clock on the
TXd line.

If anyone in the UK is interested, I've still got 20-30 left (I dumped over 300
of them)

--

73 de Robin. G8ECJ Hub manager gb7ipd

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