[AMPS] Measuring plate choke series resonance

[Bob Sutton]

Greetings ...

What is the usual method of measuring the series resonance of a plate choke?  

Probably a silly question, but could there be more than one series resonant
frequency?  

There is not much power out of my HB 8877/3CX1500a7 amp on 12M (300W) and
10M (zip!) that otherwise goes OK considering the small HT supply ... 1100W
from 160M - 17M, and (a so-so) 800W on 15M.  The tube is OK as it puts out
about 2kW in my 2M RF deck with a decent HT supply.  

I had never thought to measure the plate choke until the recent threads on
their series resonance, and had always blamed the anode circuit layout.
It's easy to see why from the picture at ... 

http://www.qsl.net/zl1rs/dxpeditions/zl8rs/amptop.jpg

When I get it back next month I will rebuild the anode circuit with the
copper tube high bands inductor next to the anode, the band switch much
nearer the tube, and the lower bands inductor between the band switch and
the front panel ... and hope the plate tune minimum + strays is not too
large for a better result on 10/12M.  Comfortable suggestions are welcome!

73 ... Bob, ZL1RS



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