Re: [amsat-bb] RE: Geo Opportunity

[Bob Bruninga <bruninga@xxxxxxxx>]

On Wed, 30 Jul 2003, Russ Renaud wrote:

> Assuming a 2 metre downlink, a 1 dBW ERP (LP) from the
> satellite and a 1.8 wavelength long CP yagi in a quiet
> location with a good preamp:
>
> satellite ERP 1dBW
> path loss -168dB
> polarization loss -3dB
> transponder loading -10dB
> station antenna gain 13.7 (dBic)
> antenna/system temperature 500 degrees k
> receiver bandwidth 2.7 kHz
>
> 10log 1.38E-23 * 500 * 2700 = -167 dB noise power

Isnt 500K a pretty poor system?  The YAGI is pointing up at cold sky.  SO
it does not see the 300K earth even.  WIth a good LNA, cant we do much
better?  Then what is the SNR?

Thanks

>
> I come up with a 1dB s/n ratio.  I guesstimated the
> system noise temperature using the VE7BQH antenna
> table at:
>
> http://web.wt.net/~w5un/144gt1.doc
>
> and then I doubled the Ta.

de WB4APR@amsat.org, Bob

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