[NLRS] 2m Amp Question...

[W0ZQ at aol.com]

Hi Scott .... something isn't right.  That's 3dB loss and 25 watts of  
power dissipation going somewhere.  If you can, check the SWR between the  rig 
and the amp ... best to do if you have a dummy load on the amp's antenna  
port, but you can use your normal antenna too.  The swr should be  essentially 
the same on the input side of the amp as the outside.

You MAY  have a dirty contact on the relay ... this happens more often if 
you are  using RF sensing to switch the amp compared to using a PTT control 
line from the  rig to hard key the amp.  A dirty contact can happen because 
the  amp's relay is being hot switch .... there is RF on it when its 
switching -  using a PTT line from the rig to key the amp helps to reduce this and 
adds  longevity to the relay(s).   
 
You can clean the relays by taking their cover off and taking a piece of  
paper, placing the paper between the relay contacts, and drawing the paper 
out -  the paper acts like a very fine sandpaper and cleans the contacts - you 
do NOT  want to use anything aggressive like a file unless there is an 
actual pit, or  burr, in the surface of the relay contact.   

Hope this helps,  good luck.

73, Jon
W0ZQ



In a message dated 5/30/2009  11:23:56 A.M. Central Daylight Time, 
kb0nly at mchsi.com writes:


Working  on a RF Concepts 2-417 today, anyone have one of these that can 
tell me what the  average loss is when transmitting through the amp when 
powered off??

I  put the meter before the amp and i get a perfect 50w, put the meter 
after and i  get about 25w, there is no way its normal to lose 25w transmitting 
through this  amp!

Bad relay?  Works fine when turned on as there doesn't seem to  be any 
additional loss on receive compared to the amp being on or off.   Thought maybe 
it was a bad jumper or something and so i swapped cables and such  to 
eliminate any other reason for it.  The amp just seems to be reducing my  power 
through it by 50%.

73,

Scott
 
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