Tom, Thanks for the details on the "Z" for TB. On a related matter I
have been looking for comparisons between a "L" and a "T" firmly believing
that a "T" would be better as in 65' up and 135' horizontal fed in the
exact center. However there are so many TB'ers using "L" rather than "T"s
which begs the question....why? You need two supports for the "L" but how
much do you gain by converting this to a "T" with even a modest ground
plain of 6-12 radials? Or is it just a matter of convenience and lot
size?
There is almost no difference between the T and L. It is mostly a matter of
what someone can fit.
When I lived on a city lot, I had restricted antenna room. I installed a
"G5RV" between two tall pines. I dropped the feedline vertically to the
ground. I fed the entire thing as T on 160, and I managed to work many
JA's, VU, UA0's, VS6, and even a JT on 160. An L I tried was no different,
but too many wires cluttered an area and makes an RF mess out of things. The
G5RV gave me a good 160 antenna (fed as a T) and a pretty good 80-10
antenna, with just one wire and one feedline, using a tuner right where the
feeder came to ground level.
I installed a 100 ft vertical later, and it was no better than the G5RV "T".
As a matter of fact I just phased the 100ft tower against the G5RV to make a
two element 160 vertical array with four patterns.
Again my question: How much better is a "T" over an "L" on 160?
No one would notice, it is not even worth one dB. We are actually lucky to
notice 6 dB unless we A B test something.
You would likely notice the out and up and out half wave, though. It is far
more like a messed up dipole than a good vertical. The one I tried lost
several dB on groundwave over a base loaded vertical. It kept getting better
and better as I made it more and more like an "inverted L".
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