On Dec 24, 8:12*pm, Tim Shoppa wrote:
On Dec 24, 4:23*pm, John Ferrell wrote:

I have been successful at modeling and then constructing transmitter
matching circuits at low power with common sizes of capacitors. Now I
want to move up to the 1 KW power level. Inductors are easy enough to
homebrew but capacitors are both expensive and scarce. Anyone have
ideas or maybe experience in this area?

DigiKey has a good selection of High Voltage units (3 KV Plus) at
modest cost but considering their size and the losses expected in the
capacitors I don't think they can dissipate the heat...

John Ferrell W8CCW

I'm guessing that you're talking about capacitors in the few pF to low
thousand pF range used in L matching etc.

(The other alternative is electrolytics in the power supply, where the
common solution since the dawn of time has been series connected 450V
units with equalizing resistors).

For fixed capacitors, a surplus source of "doorknob capacitors" is the
standard way. Not cheap or available at the corner store but they are
available. Try Ebay, where by far most of the parts you'll find are
Russian, or rfparts.com.

For variable capacitors, if you don't want to find some old
Hammarlunds or EF Johnsons or whatever, MFJ sells some new manufacture
large air variables, and other people homebrew their own out of sheet
metal, threaded rods, and nuts:

*http://www.metaphoria.us/hamradio/DL5DBM_cap_plans.pdf
*http://www.metaphoria.us/hamradio/transmatch.html

Tim.

I have had some luck cutting out non ferrous parts like this using a
router with a carbide bit. Fasten the metal to a template and feed it
into the router. too easy.

Jimmie