[TowerTalk] T-matched Driven Elements

[Frank Donovan]

Hi Mike!

Glad to hear u are making preparations for what promises to be a fantastic
contest season with the sudden but persistent resurgence of sunspot
activity!  15M has been fantastic, and expect worldwide 10M openings by
CQWW!

T-rods can be mounted in any plane that makes sense for your installation.
Mine happen are in the same plane as the elements.

The 6 inch c-c spacing between the DE and the rods is a non-critical
dimension. Just do what makes sense mechanically.  I maintain nearly
constant element to rod spacing, and the spacing between the inner ends of
the my T-rods is about 3 inches (also non-critical).

Yes, each end of the half wave balun attaches to a T-rod.  All three
shields attach to the middle of the element.

The length of the rods is non-critical, provided they are long enough!
Suggest you use 72 inch rods and use an initial trial shorting bar setting
of 48 inches.  The most critical dimension will be driven element length.
You should plan on adjusting that length a few times since your set-up
will be different than my experimentally determined length.  The antenna
models simply do not work for T-matches, so the dimensions must be
determined by trial and error...  Expect the DE to be just a few percent
shorter than the reflector (and much longer than a beta-matched or gamma
matched DE).

Good luck!
73
Frank
W3LPL
donovanf@sgate.com


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