[amsat-bb] Re: poor snr on ao 40 2nd note

["Lau, Zack, W1VT" <zlau@xxxxxxxx>]

Possible reasons for poor SNR vs. sun noise measurement.

The sun noise measurement is may be skewed by poor RF 
filtering and spurs in the local oscillator.  A simple system
with lots of local oscillator spurs and poor image filtering 
will often measure fantastically well when measured with
a broadband noise source, but perform poorly on the air.

The phase noise of the LO becomes a factor when attempting
to achieve high SNRs.  The downconverted phase noise may
actually mask weak signals.  One test is to listen to a clean
signal source and measure the achievable SNR.

73--Zack W1VT  
----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org