Linux-Hams archive - February 1998: Re: 38 or 56 KBds : How ?

Re: 38 or 56 KBds : How ?

Luis Yanes (lakvhyil.xhbkqbwg@interlife.ne.jp)
Tue, 3 Feb 1998 12:40:44 +0100 (MET)


On Tue, 3 Feb 1998, Jean-Paul ROUBELAT wrote:

> I'm preparing a fast full-duplex SHF link at 38 or 56 Kbds. What could I use
> under Linux to generate the data and to modulate/demodulate my link.

You can modulate and demodulate with a manchester modem, but isn't the best
solution in spectrum eficiency. Anyway to try are good.
You can find the PCB layout in .PS from the Matjaz Vidmar S53MV desig at:

http://www.esi.us.es/~melus/gwlelec.html#manch

> >From now I'm using SCC cards + G3RUH modems at 9600 Bds, but the fullduplex
> operation takes a lot of processing and this solution does not appear to be
> suitable for my project at higher speeds.

You can use the 38K4 manchester modems with the SCC. I've not noticed a
great overhead under jnos with a single port, but may be you can't waste it.

> I also heard of ethernet cards. But is it possible to make them running at
> these "slow speeds" ? Has somebody made such an experiment ?

No, as long as I know and tried. The lowest speed I can achieve with
the ethernet cards I've are arround 3Mbps, but there is some report
that some old cards have worked down to 2Mbps.

73's de Luis

mail: cfzaqvh.uiseomrrbn@mx.dy.fi
Ampr: eb7gwl.ampr.org [44.133.41.18]
AX25: (sorry shut down)
http://www.esi.us.es/~melus/