[NLRS] More on 902 junk

[W0ZQ at aol.com]

I have been playing around with a borrowed  spectrum analyzer and looking at 
the 900 MHz band around my urban QTH.   Connecting the analyzer directly to 
the 902 looper shows multiple significant  signals up around 930 to 940 MHZ and 
even stronger signals as close as 890.8  with lots of stuff in the 859 to 887 
range.   Putting in my small  cavity filter (two pole) drops the stuff in the 
lower ranges some, but doesn't  touch the 890.8 nor 930 stuff.  Putting in the 
big cavity (five pole)  nearly eliminates it.  I then moved the analyzer to 
tap the 902 MHz RF just  before the mixer, post preamp and post RF gain stage.  
 Looking  closely at the 902 region the noise floor is 20 dB lower with the 
big cavity  in-line at the antenna input versus no cavity. No wonder I can't 
hear a thing  without the cavity filter (except Gary).  If you live in the big 
city,  if you seem to be a bit deaf on 902, try a good cavity filter.

73,  Jon
W0ZQ 



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