# Re: squint angles and P3D

• Subject: Re: [amsat-bb] squint angles and P3D
• From: joseph v murray <k0vty@xxxxxxxx>
• Date: Tue, 24 Aug 1999 12:20:19 CDT

```Hi All

It is very early morning so please go easy on my thinker.

This thread has for some time provided questions for me.     Allow me to
pose a few questions that I hope will help me straighten out my head.

Assuming some time after P3D arrives in the planned orbit and everything
is functional.

At apogee when P3D is 1 degree above the horizon from my QTH  AND the
station I wish to work has also 1 degree of elevation to  P3D and is 180
degrees different in azimuth ( on the opposite side of the earth  from my
QTH ).

What is the gain of the P3D antenna pattern toward each station?  ( since
both stations are on the assumed edge of the -3db point of the selected
P3D antenna pattern)
What transponder bands of operation will be allowed?
At what MA will P3D change antenna or transponder ?
What  P3D noise floor exists under this condition?

Hopefully this should provide all a measure of what bands and uplink
power and down link sensitivity a station need consider for maximum P3D

Thanks for bringing this to the group Bill

Joe K0VTY
------------------------------

e, 24 Aug 1999 20:59:44 +1000 williamb@netc.net.au (William B Magnusson)
writes:
>Hi Stacy (et al),
>
>Thanks for the replies.
>
>>The whole idea of 3-axis stabilization is to keep the antennas
>pointing at
>>the sub-satellite point.  Thus, the squint angles should always be
>low and
>>not worth calculating.
>
>Yep ... that's what I'd read. The question was rather from the
>perspective
>of a southern hemisphere station where we will probably see the
>perigee
>passes where the satellite height will be low compared to apogee.
>
>>Also, the antenna/transponder selection will be made such that the
>field of
>>illumination by the antenna is appropriate for the satellite
>distance.
>
>That answers my question.... thanks Stacy.
>
>
>>
>>	ArcTan(Subsat.pt.Dist/Satellite Height) = Squint Angle
>>
>
>Thank for the formula.
>
>
>> Remember, though, that P3D will occasionally go into spin mode to
>dump the
>>momentum wheel energy, etc.  During these times, squint angles can be
>>calculated just as for AO-13.
>>
>
>
>Regards to all, Bill...vk3jt
>
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