[amsat-bb] Update on FunCube-3 / EO-79 Interference

Dani EA4GPZ daniel at destevez.net
Sun Nov 13 17:20:25 UTC 2016

El 13/11/16 a las 17:55, Scott escribió:

> I have uploaded a screen shot of my waterfall showing how the wideband
> stream comes & goes in response to activation of the transponder at:
> https://dl.dropboxusercontent.com/u/31460496/ham/2016-11-13--EO-79.png

Hi Scott,

I think that what you're seeing is just the noise floor of the
transponder. I have no experience with FUNcube-3, but your picture looks
very much like the noise floor I have seen on FUNcube-1. On overhead
passes, it's quiet noticeable, even with only a 3 element yagi.

Keep in mind that (usually) a linear transponder is running all the
time. It doesn't have to be activated by an uplink signal.

In general, AGC action may cause the transponder's noise floor to vary
with input signals. One expects that if there are strong signals the
transponder's noise floor will become weaker. This behaviour depends on
lots of design parameters, so this need not always be the case.


Dani EA4GPZ.

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