Re: [sarex] FM Deviation

["James Poulin" <jpoulin@xxxxxxxx>]

Yes me too.  I have trouble decoding many of the packets
from ISS.  I think this is caused by the lower volume.

James
VA3JPX


-----Original Message-----
From: Bernie Basel <k3baz@home.com>
To: sarex@AMSAT.Org <sarex@AMSAT.Org>
Date: Thursday, September 06, 2001 19:55 PM
Subject: Re: [sarex] FM Deviation


>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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>
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