Re: [sarex] FM Deviation

[Lou McFadin <w5did@xxxxxxxxx>]

>Yes me too.  I have trouble decoding many of the packets
>from ISS.  I think this is caused by the lower volume.
>
>James
>VA3JPX

The deviation for the packet is a totally different setting from the 
voice. It is fixed at 2.2khz for the low tne and 3.3 for the high 
tone.

>
>-----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
>>>
>>>  ----
>>>  Via the sarex mailing list at AMSAT.ORG courtesy of AMSAT-NA.
>>>  To unsubscribe, send "unsubscribe sarex" to Majordomo@amsat.org
>>>
>>
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>
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-- 
W5DID
Louis W. McFadin
ISS-HAM
Hardware Manager
----
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