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Re: Verifying AZ/EL positioner accuracy.



Fred,

One of the simplest ways to check dish pointing is to point it at the sun
and check your az and el readout against what a tracking program predicts
for the sun.  

How you do this is to view the shaddow that your feed casts inside the
dish.  When the shadow is centered the dish is pointing correctly.  If your
readout is different from the tracking program then loosen your dish and
manually rotate it until readout agrees with tracking program while still
centering the shaddow.  (obviously, if you use a BBQ dish it is hard to see
the shaddow)

If you use an offset feed dish the shaddow should fall centered at the
bottom edge of the dish.  Otherwise the process is the same.
For most small dishes used for satellites this is accurate enough.  As a
second check you may be able to see a slight rise in the s-meter caused by
sun-noise (esp. on 2401-MHz).  Expect only about 1/3 to 1/2 s-unit (one can
hear this in the speaker).  

The only reason that the noise peak would differ from when the shaddow is
centered would be if yoru feed is improperly centered or focused.

73's Ed - AL7EB
PS:  do not look  directly at the sun using a spotting scope or other such
device ...you could severly damage your eyes!
PSS: if you are using a C-band TVRO dish then your idea of will work, but
you need to obtain the az-el angles for your location.  That is more
difficult but perhaps "Heavens Above" website will do that?

 

At 07:24 PM 3/28/2005 +0100, fredf@clix.pt wrote:
>Hi,
>I will have soon to calibrate my antenna pointing too,but the dish is too
big to look inside, so i will try to use TV satelite on C or ku band.They
are geostationnary, it should be easier.On KY precision should be very
good, the question is if the tracking software gives good enought
informations. 
>
>Any other ideas?
>The moon is too big for the beamwidth too.
>
>73,
>Fred,CU8AO
>
>
>
>
>
>
> position
>---------------------- MENSAGEM ORIGINAL ----------------------
>Hello KO6TH and the Net:
>
>For a quick verification of my az/el positioner accuracy I have it track 
>the sun.
>Then go outside and see if the booms are aligned with the sun in AZ and EL.
>The shadow will also be at "minimum".
>
>If accurate,  "alles OK".
>
>If not accurate, I note the correction in AZ and EL to be right on the sun,
>and use the correction factors in the tracking software.
>
>If your 2.4 GHz system is sensitive enough, use sun noise to find the sun
>then compare your actual AZ/EL position to the software prediction.
>
>If you can acquire the satellite, try varying the az/el position to see 
>if all antennas are
>pointing to the satellite. Compare the actual best signal az/el accuracy 
>to the predicted
>AZ/el.
>
>Stan, WA1ECF
>
>
>
>
>azzzzz
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>
>
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