Hi Rob,
I agree with everything you say. I'm afraid didn't make clear the
purpose of my matching network. It does just what you suggest: when on
80m circuit routes the transmitter directly to the bottom of the 67 ft
monopole, turning it into a conventional 1/4 wave ground plane
vertical. When on 160m, the monopole becomes a shortened, base-loaded
vertical, with the required inductance and impedance matching provided
by the matching network. The shortened 160m antenna actually works
surprisingly well, although naturally it has a narrow BW of about 40
kHz. SInce I use it only on CW, that's fine with me. I'll send a
diagram and a photo to your personal email. I like your ball gap.
suggestion.
73,
Jim W8ZR
On 7/26/2021 9:54 AM, Rob Atkinson wrote:
A 1/4 w. monopole load is a low Z load; that means high current, low
voltage, i.e. it is not a voltage fed antenna. Therefore there isn't
high voltage involved. You can operate without a vacuum relay. They
are usually employed in h.v. situations such as a 1/2 w. radiator
(although there are ways of avoiding them there) and mostly in
transmitter applications such as switching plate chokes or pi network
tune caps. Of course you need an enclosure that keeps bugs out and
vents to evaporate condensation.
Don't worry about designing to survive a direct hit. Broadcast tuning
houses get destroyed by direct hits, especially positive strikes.
It's not cost effective to build to handle that. Just disconnect and
provide a better path to ground. Try using a ball gap across the base
insulator.
73
Rob
K5UJ
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