Re: QO-100

Andy G4JNT

An instinctive feeling is nagging me that the fraction of the sun in the antenna beamwidth doesn't matter when working things out this way.   But it's hard to quantify why, except that using a solar flux density and an antenna aperture assumes nothing about the source, and that it's ideally a point source

SO applicable to small antennas, but what about narrow ones which are , to all intents and purposes, in the sun's near field.
(I know that sounds a bit daft at first sight, but think about it)

On Sat, 5 Jun 2021 at 13:59, Andy Talbot <andy.g4jnt@...> wrote:
I'm also puzzled as to how that can work with arbitrary antenna beamwidth
If the beamwidth is much larger than the sun's disc diameter then only a portion of the solar flux is contributimg,  A very narrow beamwidth, ie << 0.6° will see all the  sun

I shall go and sit in the garden and either :

   A) Try to work it all out from first principles   or  
   B)  Realise the grass needs cutting and really ought to be doing that instead

On Sat, 5 Jun 2021 at 13:02, Andy Talbot <andy.g4jnt@...> wrote:
I can't make that G/T equation work with your values.
What is  k   ?

And I assume it should read
G/T = 10 * log [ 4 π k (10^(N/10) - 1) / ( λ^2 S) ] . dB/K

On Sat, 5 Jun 2021 at 12:36, Mike Willis <willis.mj@...> wrote:
Forgot to add, if the transmitted noise power is roughly the same as the solar flux that gives a handle on the gain of the transponder once you do the link budget taking into account the distance, the G/T and the bandwidth.

Mike G0MJW

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