>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.
>
>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.
The grid V requirement is such that the grid-terminating R can be 50-ohms
-- with the grid driven directly.
>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%.
What is the design Q of your tank?
>Not to mention beating up the tube just a
>bit.
>
5cx1500s are fairly rugged because the thoriated-tungsten cathode and the
unplated grid are not as delicate as an 8877's.
>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.
>
How much L?
>...
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
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