Re: [amsat-bb] 2..4ghz dishes

[K5OE@xxxxxxx]

Hi Joe.

> If you are reporting on the use of a circular polarized ( helix ) and a
>  linear polarized antenna ( BBQ dish).    What "S" units do you attribute
>  the difference in the polarization ?   

I have no way to measure the difference (right now).  As you know, theory 
states 3 dB is the delta, but that assumes from a perfectly circular to a 
perfectly linear signal.  And (another big AND), conventional wisdom is an 
S-unit is worth 6 dB.  Thus, if the world was perfect, the answer would be 
1/2 S-unit difference.

It is doubtful the signal received from AO-40 is either truly linear or 
circular--but more likely a slowly changing elliptical signal.  I noted when 
AO-40 had the 2 m telemetry beacon turned on, it would change from RHCP to 
LHCP over a few hours time.  

A good way to measure this delta might be for someone with a dish to swap out 
the feed from a linear one to a circular one.  It might also be instructive 
to note the difference between a LHCP and RHCP feed.
73,
Jerry, K5OE
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