Pete said:
>But I never knew what was being measured or what the significance of the
>"zero" point was.
The idea is to measure the ratio of RF plate volts to RF grid volts. If the
loading is too light - plate load impedance too high - there's too many RF volts
on the plate. Conversely, if too heavy, the plate swing is too low. So you set
the trim pots up so the meter reads centre zero when it's tuned right.
In GG operation, the ratio of cathode volts to plate volts is used. The system
was used in the British Army (and quite a few other armies who bought it) D11
and D13 transmitters, and in the Royal Navy NT201, all of which used grounded
cathode. It's also used in a 3-1000Z GG amp in the 1970 ARRL handbook.
73
Peter G3RZP
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