There is in the ARRL handbook a design for an end-fed dipole just like Tom
suggests. It was oriented horizontally, but I see no reason why vertical
orientation wouldn't work.
The antenna was made of coax, with 1/4-wl of sheild stripped from one end.
At approximately 1/4-wl from that point (approx. 1/2-wl from the end of the
centre conductor), a simple choke was created by coiling the coax which then
could run intact all the way back to the shack. So the centre conductor was
one pole of the dipole and the braid from the feedpoint back to the RF choke
was the other.
Of course VF was a consideration and as I recall, the choke position
required experimentation to get right.
Seems to me the big issue, once the electrical issues have been sorted out,
is water penetration, particularly with the antenna in a vertical position.
I'd be tempted in this case to get a continuous length of glue-lined
heat-shrink to cover the top radiator and extend past part of the feedpoint.
Once the length was right, I'd use another piece of glue-lined heat-shrink
to create a cap and upper mounting device.
----- Original Message -----
From: "K0PYK" <email@example.com>
Sent: Sunday, October 17, 2004 5:28 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
> * 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
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