Re: [amsat-bb] Deviation

[Bob Nielsen <nielsen@xxxxxxxxxxxx>]

I meant 3 kHz p-p (per Lyle Johnson in the TAPR 9600 modem manual),
although after I double-checked (it's been several years since I edited
the manual, sorry about that!) I found I had it backward--it is better
to be a little on the high side rather than the low side (he mentions 4
kHz as being acceptable.

Of course, this all depends on receiver bandwidth and tuning accuracy
(including Doppler shift).  You want to be operating in the
linear-phase portion of the receiver's bandpass.  If you get outside
this range, the distortion will increase the bit-error-rate.  I don't
recall the figures for the Pacsat receiver bandwidth, but if 5 kHz
works, that's fine.

Bob


On Thu, Dec 30, 1999 at 05:45:49PM +0000, Roy Welch wrote:
> Lets all be sure we are talking about the same deviation.  A deviation of
> +/- 2.5 kHz from zero deviation is the same as 5 kHz p-p deviation.  I am
> using this same deviation and am having excellect results.
> 
> Bob Nielsen wrote:
> > 
> > Brian,
> > 
> > That is much too high.  For 9600 bps the deviation should be set as
> > close as possible to (but not exceeding) 3 kHz.
> > 
> > Bob, W6SWE
> > 
> > On Thu, Dec 30, 1999 at 10:51:26PM +1000, Brian Beamish VK4BBS wrote:
> > > Hi Chaps
> > >
> > > Hope the Y2K goes well for all of you.
> > >
> > > I am interested to know what deviation others are using for working the 9600
> > > satellites.
> > > I am using a DSP-12 and a IC-275/475 combination currently the deviation on
> > > the 275 is just under 5.
> > >
> > > Would sure like to hear from others.

-- 
Bob Nielsen, W6SWE  (RN2)        nielsen@primenet.com
Tucson, AZ DM42nh  QRP-L #1985   http://www.primenet.com/~nielsen
 
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