Well, I have to admit being concerned about the possible losses in my
coax cable (RG213) capacitor that I am using on my gamma matched tower.
I have perhaps 200 or 250 pf worth of coax coiled up in a loop about
a foot in diameter.
I have never had issues with it melting, so I didn't figure too much
power could be lost - but I was still curious.
So - I just ran a test (and I do mean ran).
I transmitted with full power (1500W) for several minutes on 1805.15 -
key down (yes, that was me at 04:10 UTC). Then I ran out into the antenna
field to measure the temperature of the coax capacitor - using nothing
but my bare hands. It is currently about 40 degrees F outside, and the
capacitor felt pretty cold. I could not detect any warmth anywhere along
the length of the coax - or in the magic device at the end of it that
prevents arcing (see my previous post). After a minute, I could fell
it getting a little bit warmer - but that was from my hand (no - I wasn't
still transmitting).
Therefore, I think it is safe to conclude that the power lost in a
coaxial capacitor due to whatever losses there might be is pretty
minimal and will not have a significant impact on your transmitted
signal strength.
When you figure how cheap one is to make - and how easy it is to make
WX proof - it is still a good bargin. I did use a vacuum variable on
my 80 meter shunt loaded tower, but that was so I could QSY from the
CW to the phone part of the band.
73 Tree N6TR
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