[Collins] Help Needed Diagnosing a 30L1 Loading Problem

[Dr. Gerald N. Johnson]

The loading capacitor is NOT an antenna tuning capacitor. In a linear, I
start with it at maximum capacitance. I resonate the plate tuning
capacitor which resonates the whole output network. I monitor power
output for maximum output. I change the loading capacitor (which knocks
the plate tank off resonance), and the plate capacitor as they interact
(and that's how the servo tuned Collins transmitters did it too),
repeating for maximum output. I don't tune for plate and grid currents
because it is very possible to find loading conditions that get rated
plate and grid currents with 10% rated power output. When tuned for
maximum output, I always find the plate and grid currents are what they
are supposed to have been.

I used that technique on a Henry 2K-3 driven by a new KWM-2A at a US
MARS station used for phone patches from Nam 16 hours a day and the
increase in power was noticed by the increased signal strength in Nam.
As I recall, the Nam station said, "I see you finally got the PA turned
on."

If this tuning technique won't achieve rated power, then there could be
bad tubes, or bad band switch contacts around the loading capacitor.

-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer