Date: Mon, 4 Jul 2016 12:26:14 -0700
From: Jim Brown <jim@audiosystemsgroup.com>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Fair rite materials for choke baluns
On Mon,7/4/2016 12:01 PM, Jeff AC0C wrote:
> The G3 data on the type 52 looks pretty good. It sure seems like a
> side by side bench test of the two materials would prove to be very
> interesting.
I'd be more interested in a study of power handling, which is a lot more
difficult. A good starting point would be NEC modeling using the
parallel equivalent circuit, which should give us a handle on the
dissipation. Then subject the actual chokes to high common mode voltage
to see how they hold up.
An easy to build test fixture would be to use the choke as the end
insulator of an end-fed center-fed dipole, as I've shown a couple of
places, and shove high power at a high duty cycle into the dipole. That
test hits the choke with rather high common mode voltage. Blast it for a
while, then go feel it for heating and inspect it for any damage. The
choke in question seems to be resonant in the range of 15-20 MHz, so a
suitable dipole should be easy to rig.
http://k9yc.com/VerticalDipole.pdf
73, Jim K9YC
## yes a type 31 vs 52 would be a good test, using various winding
techniques.
I don’t know if a vertical dipole using a CMC as an end insulator is a good
test
for a CMC or not. It’s a one off extreme case antenna, that most will not
use.
However you could easily get to the CMC to measure heating. What else that
would
work is installing the type 31 / 52 CMC right at the feed point of a
rotary dipole or
a 3 el yagi. You could feel any heat with both those ants. If it turns out
that the dipole
/ yagi exhibits minimal heat vs a vertical dipole and CMC used as an end
insulator, the
results may well be more useful.
Jim VE7RF
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