Here's the deal, I'm 'converting' a 2KW 13.56mHz plasma generator for =
160 thru 10.
The basics: 5CX1500A, 3.8KV EP. Got it running 'stock' (class C) =
before conversion, easy 2KW output. =20
Conversion: added 1000pf loading vac var (was fixed), bandswitch, new =
tank coils, reworked screen supply from fixed 500V to zener regulated & =
switchable 600V to 750V, reworked bias supply. Input circuit is 200 ohm =
resistor /w 1:4 broadband toroid.
Most of this freely copied from Rich Measures web pages.
Been tearing my hair out trying to get anything over 1KW output. =
Efficiency lousy - 25% to 30%. Not to mention beating up the tube just =
a bit.=20
I had initially built the output circuit using a small (.3uH) plate coil =
to offset the high output C of the tube. Figured I was fighting some =
miscalculation... So let's make it simple....
Tore out the tank coils, ripped out the .3uH plate coil, wound a coil =
for 40M out of 3/16" tubing, ran it directly between Tune and Load caps =
- no bandswitch (no cobbled up piles of tubing & coil stock). Same =
results. =20
Tuning seems OK, definite plate dip, screen rise, output rise. Loading =
is mushy, can crank the cap forever with very little change. I have a =
fairly good L/C meter & preset both tune & load per the calculations, =
tune is real close, load is mush, efficiency stinks.
Other stuff: filament volts is right on, checked output with 2 different =
Bird wattmeters.
So.... what's the secret?
Thanks for reading all of this. 73, Bill
~~~~~~~~~~~~~~~~
Bill Coleman N2BC
http://home.stny.rr.com/n2bc
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