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
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