At 09:58 PM 6/23/99 -0500, you wrote:
> TV doorknobs were not designed
>to handle a great amount of RF.
Absolutely, but thats not to say they won't handle it under the proper
circumstances.
>RF rated caps are rated in amps of RF at selected frequencies.
>TV doorknobs have no such rating. Absolutely, but then neither do many so
called " RF caps ", at least not so you could find.
>That depends on several factors. You are painting with a very broad brush
>here.
>The current in Cblock is dependent on frequency, Ip, Ep, and the output
>capacitance
>of the tube(s). As frequency is increased and the tube(s) output
>capacitance
>constitutes a significant portion of the total tank capacitance, a
>significant portion
>of circulating tank current flows through the blocking capacitor. A cap that
>would
>get by on 160 meters may crispy critter on 10 meters.
Interesting points you make here Phil, and I mostly agree, but I'm not sure
the conclusion is valid. RF caps with current ratings on them typically
have much less current capacity on 1.8 mhz then they have on 28 mhz. I
think I know why, but would rather have our staff scientists expalin it. In
any case, that charateristic would make them work as well or better on the
higher frequencies even with the anode "C" causing a higher current through
them.
I recently rebuilt a Bird dummy load. To check it out, I ran key down 1800
watts out on 24 mhz for twenty minute periods on multiple occasions. It all
went through the four pictured TV doorknobs. They take a lickin' and keep
on tickin'!
>Not me! I buy my RF rated doorknobs by the pound at the local radio factory
>junk yard.
You really know how to hurt a guy!
73,
Larry - W7IUV
w7iuv@arrl.net
http://www.axtek.com/w7iuv
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