Pete,
There's a small plastic spool with wire wrapped around
it that forms the RF choke on the HF bands. I'm pretty
sure it's also a "matching" coil since the reactance will
vary band-to-band.
If something happens to that coil or its connections,
it is potted in bee's wax that can be removed (melted out)
with a soldering gun (with a long homebrew tip on it) or
possible a heat gun if the temperature can be controlled.
I *think* I have more details about that "choke" if you
need to know....wire size, number of turns, etc.
I modified my 18AVT for portable use and I use it on
just about every Field Day....fits in a ~3-ft canvas bag
with coax, tripod stand, tools, etc.
73,
Charlie, N0TT
On Mon, 10 Mar 2014 12:13:46 -0400 Pete Smith N4ZR <n4zr@contesting.com>
writes:
> I recently bought a very old 18AVT-WB which, after working for a
> while,
> is no longer resonant on any band, or even close.
>
> Brought the base section into the house, and it appears to have a DC
>
> short from center to outer conductor of the SO-239, but when I test
> with
> MY MFJ-259B, the short is not present at RF.
>
> Can anyone tell me if, as it appears, this vertical has an RF choke
>
> inside the molded plastic base shunting the output for lightning?
>
> --
> 73, Pete N4ZR
> Check out the Reverse Beacon Network at
> http://reversebeacon.net,
> blog at reversebeacon.blogspot.com.
> For spots, please go to your favorite
> ARC V6 or VE7CC DX cluster node.
>
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