[NLRS] Trouble shooting my 2304

[W0ZQ at aol.com]

I think I have my 2304 receive back.   Last year I blew the front  end FET 
and replaced it ... on the DEM 2304 you have to lift the PCB off the  metal 
pallet heat sink else you can not generate enough heat to  solder.   In doing so, 
it appears that I may  have cracked the 8.2pf feed thru cap that runs from the 
gate of the FET to  the receive SMA input connector.   The unit would 
receive, but it  was deaf when trying to work weak signals.   The damaged cap was not 
 visually obvious under a magnifying glass.   However, with the receive  side 
terminated with a 50 ohm load and listening to my weak signal source, I  
could carefully touch the FET side of the capacitor with my soldering aid tool  
and the signal would jump from S2 to S9 + 10 db.   This was a good  sign from 
the standpoint that the front end was most likely working, at  least at some 
level !     I would then touch the antenna  side of the same cap and the signal 
would go from S2 to S5.    It  seemed to me that the signal increase should be 
the same, or very close to the  same, regardless of which side of the cap I 
was touching.    I  replaced this cap and my weak signal source is now S5 and 
jumps to S9 + 10 dB  regardless of what side of the cap I now touch.   I think 
its  fixed.
 
Lessons learned.    1)  Weak signal sources are good  trouble shooting aids.  
 2)  Its not always the FETS that cause  problems, watch out for cracked 
surface mount caps.
 
73, Jon
W0ZQ