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R: Pointing large dishes



Roger WB0GAI,

A 10' ( 3 meters) dish at 2400 MHz has a lobe like a pencil of  3 degrees
at - 3 dB points.

Since the AO40 inclination is 7.53 degrees the satellite subpoint latitude
will change from -7.53° South to + 7.53 North during one orbit.

If you use a polar mount you will loose about 3 dB of signal strenght
everytime the subpoint latitude changes by - 3° South and + 3° North with
respect to the equator.

In order to know how many dB of signal strengt you will loose when AO40 SSP
latitude culminates at -7.53° S and +7.53° N you must look at the polar
radiation pattern of your 3 meter dish

Considering that the boresight gain of a 3 meter dish at 2400 MHz is 35 dBi
i am pretty confident that polar mount will work in your case.

In any case i suggest you to simulate the polar radiation pattern of a 35
dBi gain dish using any antenna program and you will see how many dB the
signal drops at +/- 7.5° from boresigth.

Than you have the data to decide.

73" de i8CVS Domenico

----- Original Message -----
From: Roger <rogermj01@attbi.com>
To: <amsat-bb@AMSAT.Org>
Sent: Thursday, August 01, 2002 5:38 AM
Subject: [amsat-bb] Pointing large dishes


> have recently acquired a 10' TVRO dish and would like to use it for AO-40.
> I recall that when some folks were first trying to use the large dishes
the
> claim was made that AO-40 closely followed the ecliptic and that leaving
it
> set as a polar mounted system would work.
>
> I wonder if anyone actually made that  happen. I am willing to engineer an
> az el system but there will be a lot of adapting to do.
>
> Any help or ideas would be appreciated.
>
> Roger
> WB0GAI
>
>
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
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