[AMPS] RF Concepts Amplifier Question

[Jon Ogden]

Hi all,

I have an RF Concepts 4-310 UHF brick.  It's spec'd to put out 100 Watts 
with 30 Watts in.  However, I get power different from that!

I finally have a power meter for UHF so I decided tonight to check out my 
432 setup and see how much power I was really getting out.  On 432.200, I 
found out that I was getting only about 60 Watts out of the amp with 
about 30 Watts of drive.  I checked the voltages and opened the amp up.  
Voltage right at the collector choke is around 13 Volts.

The I decided to tune up and down the band.  My output power gradually 
increased to around 90 Watts right around 439 MHz.  Then in the FM 
portion of the band it dropped down to around 80 Watts.  

The amp consists of two MRF648s driven in parallel.  At the point where 
the input microstrip splits to go to each transistor's base, there is an 
adjustable cap.  Adjusting that tunes the amp so that I can change where 
the power peaks.  If I peak the power down in the small signal portion of 
the band, I can get a max of about 80 Watts.  This is then the maximum I 
can get out and everywhere else on the band is either the same or lower.  
There are no other adjustments except for a couple of bias pots and the 
pot that controls the release timing of the relays.  Adjusting the bias 
pots doesn't seem to do much.

So I am at a loss here.  Is this typical behavior for this sort of amp?  
Operating 40 Watts below its specified power in some parts of the band 
and 10 Watts below rated power in others?  Or do I have a bad device??

Any help would be appreciated.

73,

Jon
KE9NA


-------------------------------------
Jon Ogden
KE9NA

http://www.qsl.net/ke9na    <--- CHECK IT OUT!  It's been updated!!!!!


"A life lived in fear is a life half lived."


--
FAQ on WWW:               http://www.contesting.com/ampfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm