RE: 300bps Packet

["Tsutsumi Family" <oakie@kamakuranet.ne.jp>]

Dave,

Thank you for your quick reply.

Along with Phill's configuration parameters i.e. f0=900Hz and f1=1,100Hz in
the separate correspondence, the conclusion seems to be that f0 and f1 must
be any arbitrary numbers below 1,200Hz and above the low cut frequency of
his/her TX/RX audio path with 200Hz gap.

As the above conclusion is unique nature of the soundmodem, the fact should
be widespread to the new 300bps AFSK SSB users of the soundmodem and I hope
Andrew's pointed sites will kindly cover this.

Regards,

take

de JA5AEA
-----Original Message-----
From: linux-hams-owner@vger.kernel.org
[mailto:linux-hams-owner@vger.kernel.org] On Behalf Of Dave Platt
Sent: Thursday, November 25, 2010 3:37 AM
To: linux-hams@vger.kernel.org
Subject: Re: 300bps Packet

Tsutsumi Family wrote:
> Dave,
> 
> Thank you for providing the tutorial of SM source codes.
> 
> As one of ways to solve 300bps SSB operation without any code change, you
> are suggesting to use the frequency setting of f0 and f1 to less than 4 x
> 300bps =1,200 Hz such as 800Hz and 1,000Hz, not conventional 2,100Hz and
> 2,300Hz.
> 
> Correct?

Correct - I think this ought to work.  As long as you don't pick
frequencies so low that your audio connection (PC to rig) is
rolling off the amplitude (due to e.g. transformer isolation
in the audio path) this approach should let you generate a pair
of tones with a suitable separation.

You'll just need to tune your sideband rig a bit differently than
if you were using a traditional "hard" TNC with its receive filters
tuned for a 2200 Hz channel center.  Just tune to match up the
tone you hear during reception, with the tone that your PC generates
during transmission... it'll be an octave or so lower than the usual
pitch but it should work.



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