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Re: AO-40 reception question




  Bill,

   Don't forget that early on, the attitude of the
spacecraft was such that good squint angles (when they
occurred) were at a far closer range than they
are now, so yes, signals would have been stronger 
(and of course S1 was VERY strong! :^)

  I've found that a DSP filter in random noise reduction
mode does a lot to improve copy.  It's more  fatiguing to
listen to, but definately more complete  copy for weak
signals.  

 -al
  WB1BQE


Bill Howell wrote:
> 
> When AO-40 was first turned on for amateur use, I was able to hear
> others' downlinks
> well enough for an SSB QSO (sigs were in the noise, but useable).
> 
> Lately, it seems, (using the same equipment: Meyers dish, unmodified
> 3733, ft-847),
> all the downlinks seemed to be down deeper in the noise and not
> strong enough for a QSO.
> 
> I have swapped the 3733 with another one, with similar results. I
> also tried using a different
> wall-wart / bias-tee. No difference.
> 
> I recently added a DEMI preamp (recently tweaked by DEMI), between
> the Meyers feed and the 3733.
> The signals are helped by the preamp, although they are still pretty noisy.
> 
> I get S-5 background noise (away from the beacon freq), on the '847,
> and the beacon itself is at S-6.
> 
> I know that on some passes, I was looking through a tree, but one
> particular pass
> was clear of the tree and still weak (could be a combo of good view /
> bad squint).
> 
> I have a couple more things to try. I have the K5GNA filter to
> install, and I need to try cutting the stub.
> 
> A friend of mine is also using an unmodified 3733 and finds downlinks
> only strong enough
>   for CW QSO's.
> 
> Perhaps all this is just tree / squint related, but in general, It
> just seems like conditions
> used to be better.
> 
> --
> 
> Bill Howell
> University of Texas at Austin
> College of Fine Arts
> Office of Computing Technologies
> N5ALO  Amsat 32459  QRP-L 415
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