----- Original Message -----
From: "K0PYK" <k0pyk@yahoo.com>
To: <towertalk@contesting.com>
Sent: Sunday, October 17, 2004 3:28 AM
Subject: [TowerTalk] Vertcal Dipole
> Tower Talk'ers,
> Has any made a vertical dipole (lets say for 20
> meters) where it is end fed with coax. I will try and
> explain my thoughts;
> * top half of radiator, i.e., 1/2 of dipole is a
> single 14 guage wire.
> * bottom half of dipole would be coax...the center
> conductor would feed the top half inside the braid.
> * the bottom half of vertical dipole would be the
> outside braid of the coax.
> * the bottom half of the dipole would be fed from the
> bottom and end where the top half starts.
> * a decoupling device may be needed at the bottom of
> the dipole...1-1 balun???.
> * I realize that normally dipoles are fed in the
> center.
> * A person could use some type of tubing for the
> bottom half and still feed it in the center, but I was
> looking for something that would be portable and you
> could just hang up vertically or horizontally.
> I look forward to your thoughts.
> Thanks in advance,
> Tom, K0PYK
>
One of the antenna compediums has a 4 element vertical phased array for
80(?) that used loaded center fed vertical dipoles. They ran coax up the
tube.
The tricky thing about what you propose is feeding the bottom half at the
high impedance end, while feedng the top half at the low impedance end (the
center).
If you want something flexible, how about using some sort of triax cable for
the lower half? Or, perhaps, a piece of shielded twinax. That would give
you a "tube over a feedline" so you could feed both halves at the middle?
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