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Re: AO-40 beacon question



Jon,

Somebody did a superb job of charting the signals received as a function of 
squint.  I can't remember who did it, but my simple (and perhaps 
inaccurate) recollection is that the small helix does have lobes, so 
sometimes you hear it better at slightly higher squint, than lower squint; 
also, at certain squints the spacecraft gets in the way of the helix's view 
of the earth.  I think it was in the 50 deg squint range, which seems a bit 
out of the range you were having troubles with yesterday.

Perhaps you can dig up that information on the amsat-bb...seems like it was 
one of friends from down under, or maybe a UK fellow.  It was very good, 
from a collection of many orbits.

73,

Mark

At 07:31 AM 3/02/03 -0600, you wrote:
>All,
>
>The fellow from Washington state that is having problems hearing AO-40
>brings up a question that I have that I noticed yesterday.
>
>I was trying to hear the beacon yesterday when the satellite was about
>30,000 km in elevation and the squint was about 33 degrees.  I think the MA
>was around 30 or so at the time.  The bird was at about 180 degrees and 35
>degrees elevation for me - in the clear.
>
>I heard nothing, squat, zip.
>
>The beacon is supposed to be on for the whole orbit now, so unless there was
>one of those "glitches" it should have been copyable I though.
>
>But then I had the following question:
>
>Is it possible at certain heights and certain squints to be out of the beam
>of the S2 antenna?  Even though I can "see" the bird, is it possible that
>the elevation is too close to earth and so the antenna pattern is two
>narrow?  That coupled with the squint could make it such that some people
>could hear the beacon when others can't.
>
>I haven't looked at the specs of the S2 antenna.  I know this sort of thing
>would have been an issue with the S1 antenna with its higher gain and narrow
>pattern.  But could it happen now?  Was just trying to make some sense out
>of why I couldn't hear it.
>
>A half hour later or so and I heard the beacon fine.
>
>73,
>
>Jon
>NA9D
>
>-------------------------------------
>Jon Ogden
>NA9D (ex: KE9NA)
>
>Citizen of the People's Democratic Republik of Illinois
>
>Life Member: ARRL, NRA
>Member:  AMSAT, DXCC
>
>http://www.qsl.net/na9d  <- Updated on 1/22/03!!!
>
>"A life lived in fear is a life half lived."
>
>
>----
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Mark L. Hammond  [N8MH]


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