At 19:14 11/13/2007, you wrote:
>[snip]
>I used some Caddock power resistors in the grid circuit of the
>"Sunnyvale/Saint Petersburg Kilowatt Plus" that appears in the 1999-
>2004 ARRL handbooks. They are mounted on a pretty big heat sink, and
>have their own fan. This setup has been very satisfactory, and
>capacitance hasn't been a problem.
I did a ballpark calculation of the capacitance of one Caddock MP9100
unit, and came up with 5pf. Using that value with their specified
inductance of 20nH gives a self-resonant frequency in the order of 500 MHz.
Wiring four of these units in series/parallel would produce a 400
watt power rating. If mounted taking great care to minimize lead
lengths, the self resonant frequency of that array would not be much
lower than that of a single unit. Should be able to use these at HF
without compensation.
Interesting! Anybody know what these units cost? ... couldn't find
them in my DigiKey catalog
Cheers
Rod VE3UW
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