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# Deviation Levels? - PacSat related

• Subject: [amsat-bb] Deviation Levels? - PacSat related
• Date: Mon, 28 Feb 2000 10:01:30 -0500

```Ok, all you experts out there... I've got a pretty simple question.

First some basic assumptions.

On the pacsats, I'd expect the deviation to be as follows for the various
modes

1200 - AFSK - 3.75khz +/- .25khz
1200 - PSK(FM side) - 3.75khz +/- .25khz
9600 - FSK - 2.75khz +/- .25khz

Is the above a valid assumption?

Second.  I have a service monitor (an HP 8920A for those that might know),
that allows you to look at deviation with a direct feed from the TX output
of the radio being tested.  It also has some filters that can be selected to
shape the audio.

Basically, it has a HP that can be <20hz, 50hz, 300hz, and C-MESSAGE (cell
stuff)
It also has a LP that can be set to 300hz, 3khz, 15khz and one other value
that escapes me at the moment.

If you look at the deviation readout on the unit when it's looking at 9600
baud data, with it set to the default (50hz HP, 15khz LP or 50hz-15khz BP),
you see let's say 3khz or deviation.  When you set the HP to <20hz, the
deviation goes down to say 2.5.

I've done some research and it looks like 9600 is suppose to have a
frequency response of DC to 7.2k.  It also is suppose to have a deviation of
3khz at 4.8k.

Ok, with that said, anyone want to take a shot at how to setup the deviation
with this monitor?

One final comment.  The unit does have a "scope" (o-scope) that can look at
the wave form of the signal and you can select the vertical range in khz.
So you could set deviation that way as well.  What I don't remember, is
whether the filters are in effect when you look at that.  I think they are.

I'd also be curious of proposed setup for the 1200 baud modes.  Do you set
the dev the same for AFSK and you do PSK?