[amsat-bb] Re: AO-40 signal strength

["Stacey E. Mills" <w4sm@xxxxxxxxxx>]

Roy Schulz said:

>Hi All,
>
>I was working this mornings AO-40 pass, between MA 200-246, and noticed that
>both the beacon signal and other station's signals were very strong. The
>squint, according to the latest info of ALON/ALAT 53/30, ranged from 37 down
>to about 20 degrees during this period at my location.
>
>The consensus from everyone that I talked to was that the signals were much
>stronger than the apparent squint info would suggest. In fact toward the end
>of the pass I was down to about 1 watt of uplink power on L1, which I
>normally only get down to when the squints are below 10 degrees.

Yes, but what was the current range vs. the comparison range?   That's 
really critical.
At MA =240,  AO-40  is about 1/4 the distance at apogee and dropping 
rapidly.  At MA =246, it's about 1/5 the distance at apogee and dropping 
even faster.  One quarter the distance = 16x (12 dB) stronger signal for 
the same squint.   Also, because ALAT is raised, squints don't change as 
fast as when ALAT=0, so reasonably good squints last longer towards perigee.

>So, to the question;  is the current alon/alat info in fact correct, or has
>everyone upgraded their stations to 30 foot dishes while I wasn't looking,
>hi..?

The ALON/ALAT are based on solid photographic + solar data.  These are the 
same techniques and calculations that we have used for almost  two years of 
satellite control.  If we had a procedural/software error, we'd know it by 
now.  The camera images and solar sensor data are available from the 
amsat-bb archive if anyone wishes to have a go at deriving the values.  As 
noted, ALON is decreasing at about 20 deg/week or 2.9 deg/day, so ALON is 
now a bit less than the posted value.   As ALON decreases, minimal squint 
will occur at greater range and the signals won't be as good.



-- 
  _______________________________________________________________________
  Stacey E. Mills, W4SM    WWW:    http://www.cstone.net/~w4sm/ham1.html
   Charlottesville, VA     PGP key: http://www.cstone.net/~w4sm/key
  _______________________________________________________________________

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