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Re: "Precision" Antenna Pointing



Bob,

Glad you made the calculation.  This will give others a benchmark by which
they can evaluate their S-band systems.  Of course this method depends on a
recent solar flux measurement in your area of the world, since solar flux
varies  in just hours.

Although this was published in the SETI community, it has value for anyone
evaluating a antenna and receiver above 432 MHz.  Dick Flagg gets the
credit for the development of the procedure; I merely made the spreadsheet
for convenience.  You should be aware that there is an error in the noise
figure algorithm {which I haven't goten around to fixing}.  The program is
on the optimistic side when calculating system NF by around 10 %.

You will find a good program for finding system NF on the SETI-League
software page called T-calc.  You can modify my spreadsheet to input system
NF {noise temperature} directly using the result you get from T-calc.

Ed

>From: Bob Snyder <kd1vv@mediaone.net>
>I used Ed Cole's g-t.xls spreadsheet (available for download at
>http://www.setileague.org/software/spreadsh.htm ) based on Richard
>Flagg's equations and instructions given at
>http://www.setileague.org/articles/g-t.htm
>
>The current solar flux at 2400 MHz is around 140 (interpolated from
>http://solar.sec.noaa.gov/getftp.cgi?get=lists/radio/rad.txt ).  Using
>0.8 dB noise figure and a 24 dBi antenna, I get an excess sun noise (Y
>in the equations and spreadsheet) of 4.2 dB.
>
>73,
>Bob KD1VV
>
>
>Clifford Buttschardt wrote:
>> 
>> I confirm your thought about plus/minus two degrees as good as amateurs
>> usually can obtain.  It would be nice if ordinary antenna hardware would
>> do better.  This is barely good enough for S band use even with a two foot
>> dish.  Can we list here how much excess sun noise is gotten on 2400 MHz?
>> Be sure and include you antenna system and noise figure if possible.
>> 
>> As for determining the sun's Az/El.  All tracking programs have it listed.
>> Instrack displays it constantly.  Cliff K7RR
>> 
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