I currently have a wire T-vertical with a 75-ft. vertical portion and a 75-ft.
topload wire over about 60 radials.
Feedpoint is around 25 + j0 at 1.825 Mhz, which I match with a toroid 1:2 unun.
The latest issue of QEX has an article about maximizing radiation resistance by
putting the current maxima halfway up the vertical.
EZNEC shows me that by extending my T topload wire to 140-ft. long, the current
maxima will move up to the middle of the vertical, and my feedpoint will be
around 37 + j238 at 1.825 Mhz. I would replace the unun with a switched or
adjustable L-network for matching across the whole band, and perhaps other
L-networks for 80 or 40.
A couple questions for the group....
1. Supposedly I will end up with higher radiation resistance and efficiency,
and I assume higher effective radiated power. But what am I giving up?
2. Should L-networks be located in an RF screened enclosure? I have a large
plastic NEMA enclosure I can house the whole matching show in, but should I
line the interioir with screening of some sort?
Thanks,
Steve
KK7UV
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