[VHFcontesting] The 222 MHz amplifier project Update

[David Olean]

Hi VHfers

I have five amplifiers all built and tested to bring to Central States. 
It is a good thing that I tested them as I found a few trouble spots. 
Nothing too serious. The first unit powered up and ran up to 1000+ watts 
with no trouble. I cranked the drive up to a bit over 1500 watts out and 
it shut down for a VSWR fault. I unplugged the coax and measured the 
load at 222 MHz. It was 33 dB return loss so should not have tripped. 
Turns out I was getting a squirrely result with rf getting into the 
reflected part of the directional coupler. I cut up and bent a shield to 
go over the sensor part, and that tamed it down. So I had to make 
shields for all the amps.  Then I got thinking that it needed some 
delrin feet so the amp does not mar the finish on your dining room table 
when you plop it down to show the XYL.  So I made  bottom covers for all 
the amps and turned some delrin feet on the lathe.

All the others worked fine but one was missing the reflected power wire. 
(?)  I must have been tired.  I fixed that, and the only other problem 
was that one of the DC switches got real hot during TX with 1000 watts 
out. I took it apart and added heat sink compound and made sure all was 
sitting properly in the holes. A second try was successful. The switch 
seems rather cool.

I ran one of them for quite awhile at about 700 watts out to see the 
heatrise on the heatsink. It went over 44 degrees and the fans stayed on 
after the TX shut down.  I have two 24 VDC fans on the pallet. Maybe it 
wants two more for real high duty operation.

Now to figure out how to pack them up for the trip. I am leaving at 2AM 
and heading for Little Rock with the amps. They look great in my 
opinion. heh heh.

73

Dave K1WHS