abnormallly high plate current

Lane Zeitler Ku7i at WORLDNET.ATT.NET
Wed Jan 5 21:58:57 EST 2000

For some reason I am getting higher than normal plate current in a single
3-500Z amp. On 160 meters with 400mA of Ip and 3500 volts under load the amp
is only delivering 500 watts of output.

On 80, the Ip is 400mA with 3500 volts on the anode and the output power is
only 600 watts.

Seems that the efficiency is way way down. The other bands are similar to
this. With 3500 volts on the plate at 400ma I would expect at least 850
watts out if getting around 60% efficiency.

What would cause this? The values of the pi output network C1, L, and C2 are
very very close to what the formulas say they should be. I wonder if my
plate choke is absorbing some of the power? Something is definately not


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