A few months back there was some discussion about the tunable antenna
matching network in Mastr II station PA's. I thought I'd throw out some
measurements I made today on a 100 watt UHF, 450-470 split (unmodified)
operating at 442.550.
With the antenna network tuned per the GE instructions, current draw was
29.0A at 13.80V (13.80V measured at the ring lugs at the end of the
power cables). This equates to an efficiency of 24.99% - 300 watts of
heat. The relative reading on the DVM at the test point on the antenna
network was 0.92V.
With the antenna network re-tuned for best efficiency (which is how I
always tune them), current draw was reduced to 22.6A for 100 watts.
This is an efficiency of 31.6%, 216 watts dissipation. With the network
tuned like this, the relative reading at the test point was 2.82V.
Note that the current draws cited above were for the whole station, not
just the PA, so in reality, the efficiency of the PA by itself is a
little better (and the dissipation a little lower) than what was stated
above. I'm guessing the station sans PA consumes maybe 10-15W, the rest
is the PA.
--- Jeff
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