Re: [sarex] FM Deviation

["Bernie Basel" <k3baz@xxxxxxxx>]

I have commented before on this and it was suggested that it is more of a
training them a hardware problem.  Sometimes the audio is booming and other
times the audio is weak, I guess we need to "break-in" the new crew.


Bernie, K3BAZ


----- Original Message -----
From: "Alderman, James" <aldermaja@tycoelectronics.com>
To: "'sarex@amsat.org'" <sarex@AMSAT.Org>
Sent: Thursday, September 06, 2001 1:04 PM
Subject: [sarex] FM Deviation


> Greetings Fellow Amateurs and Space Enthusiasts,
>
> >From my office here in Dallas, I was able to easily copy the ISS contact
> with the school in Houston this past Tuesday.  It was about 3/4 scale
signal
> strength for most of the contact, then abruptly dropped to nothing as the
> station dropped below the horizon.  I have copied the signal from the
> station several times on my talkie.
>
> However, there is one thing I've noticed every time.  It seems like the
> deviation of the FM voice signal is rather low.  So far I have not set up
to
> measure it on my communications service monitor during a contact, so I
can't
> tell you exactly how low it really is.  I do want to measure this
sometime.
>
>
> My observation is that I must always turn the radio volume all the way up
in
> order to hear the ISS well, while I can normally hear local stations
clearly
> with the radio volume turned about half way up.
>
> Perhaps the deviation is intentionally set low to keep the signal
> narrow-banded, thereby concentrating a maximum amount of RF power on the
> operating frequency.  This would perhaps allow the ISS station to
> communicate during weak signal conditions when it otherwise might not be
> able to.
>
> However, since the ISS must be overhead if you are to hear it, and since
> it's not really that high up (230-240 miles), it would seem that under
those
> conditions we either have AOS or we don't.  I doubt if 2kc vs. 5kc of
> deviation would make any difference.
>
> I'd be interested to hear whether others have noticed this apparent low FM
> deviation situation.  Does anybody know why this radio was set to such a
low
> deviation?  I know that the MPA radio's deviation is adjusted with
software.
>
> 73, James Alderman, KF5WT
> Dallas, TX
>
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