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[Fwd: Re: AO-51 Report fm FM-15]



Blah, forgot to reply to all, here is my reply to KF4OTN

Ryan, KB0JQO
Subject: Re: [amsat-bb] AO-51 Report fm FM-15
From: Ryan Butler <rbutler@tsss.org>
To: "Eric H. Christensen" <kf4otn@earthlink.net>
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Date: Fri, 30 Jul 2004 09:38:49 -0500
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On Thu, 2004-07-29 at 21:43, Eric H. Christensen wrote:
> Heard AO-51 come and go without making any contacts.  :(  Oh well, hopefully
> the next pass at nearly 0400Z will be better.
> 
> I noticed some times that I was getting a really clear carrier without
> audio.  It was actually covering up some stations that were working the
> bird.  Not sure what it was but noticed it throughout the pass.  Actually
> received signals up to S4 on the FT-51R using an arrow antenna.  Will be
> monitoring the next pass at 0351Z to make more contacts.  Looking for my
> first contact with W0EEC...
> 

In the email detailing AO-51's FM transponder operation, It says there
is the equivalent to a 1 second kerchunk filter (67.0 hz pl must be
present for 1 second continuously)  and then a 10 second tail (after
losing 67.0 Hz signal.  I think the clear carrier everyone is hearing is
just the "tail timer".  That being said, with everyone that is trying,
why are we hearing the tail timer?  My current theory is that the pl
decoder on AO-51 is much more stringent than that on SO-50, and is less
tolerant of hetrodynes and noise from multiple stations trying to
capture the receiver.  

The fact that it's about impossible to work over crowded areas coupled
by the reports from the sparsely populated areas that its easy to get
into as well as the command stations having relatively little problem
accessing the bird before being open to general use would support this
theory, but that's all it is, just my observations and one plausible
explanation.

An explanation from the command team on whether the clear carrier is in
fact the 10 second tail would be reassuring as well.

The pass I worked I managed to get in full quieting for 1 transmission
only for the whole pass, the rest of the time even with the dead carrier
I got no inkling I was being heard.  I started out around 10-12 watts
and ended up at full power on the 821H which I think is around 45 on 2m
into a 5 element fixed elevation linear yagi.

Ryan Butler, KB0JQO
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