Re: [amsat-bb] Using C band polar mounts w/ ao-40

["Edward R. Cole" <al7eb@xxxxxxxxxxxxx>]

Bob,

Oh, I agree whole heartedly.  In fact I said it would stand a little more
scrutiny.  The 3m dish will have a about 36 dBi gain at 2400 and a 3 degree
HPBW, so perhaps setting the position to see 3 degrees declination would
split the difference adequately and with the extra gain one could tolerate
some small off pointing gain loss [probably less than 6 dB].  I don't think
you will even need to remove any panels from the dish [this might be
important to other family members TV watching].  The feed should be placed
underneath the main TV feedhorn so that the small offset angle produced by
its position will favor the desired direction [+3 dec.].

One caveat, this is OK for receiving.  If used for uplink at 1269, the
effect of harmonic energy on the LNA's might be bad [smoke!].  So if you
have a dedicated TVRO dish you can optimize it for satellite operation.  If
you just share it, should work out fine for receiving [add 10G and 24G to
this].

Ed
Who will be first to try this out?

>From: Bob Bruninga <bruninga@usna.edu>
>On Sun, 22 Apr 2001, Edward R. Cole wrote:
>
>> The dish will still not track AO-40 over the entire orbit since it is on
>> essentially an equatorial mount.  AO-40 will appear to vary from +5 degrees
>> from the equatorial plane to some angle below it depending on MA. 
>
>But I think the beauty of this is that AO-40 is only below the equator
>during perogee (3% of the time) and  you would have to live at low
>latitudes to see it anyway...
>
>To me, the simplicity of using a TVRO mount for small inclination 
>orbits certainly gives credence to looking more closely at the simplicity
>of Geosynchronous-Transfer-Orbits for amateur microwave payloads...
>
>Further, since the gain of the 3m dish is more than adequate, then
>removing some of the mesh along the top and bottom of the dish would
>widen its Vertical beamwidth allowing for much more slop in inclination
>while retiaing plenty of horizontal gain.  Thus, I would recommend
>placing your 1/2 wave Sband dipole Vertical so that you get the full dish
>gain in the horizontal plane and less gain (and therefore wider beamwidth)
>in the vertical plane.  Then movement of the satelite up and down by 5
>degrees or so wont matter much if any...
>
>de wb4apr, Bob
> 

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