[Antennas] Feeding vertical triband dipole

[Alex]

...would it be too complicated to replace the lower half of the mast with an
aluminum pipe large enough to carry the coax inside? That way you keep it
out of the field. We were doing it on 6meters and it worked not badly. Thin
walled aluminum pipe could be a not quite so expensive alternative to the
fiberglass pole, and it's light too. That way you'll need just one choke at
the base of the antenna and that's a minimum field point!
Alex	4Z5KS 

-----Original Message-----
From: antennas-bounces at mailman.qth.net
[mailto:antennas-bounces at mailman.qth.net] On Behalf Of Igor Sokolov
Sent: Thursday, May 28, 2009 4:53 AM
To: C. Whitaker; antennas at mailman.qth.net
Subject: Re: [Antennas] Feeding vertical triband dipole

Well,I think I shall try to explain the my configuration better. The 
vertical dipole for 20-15-10  is going to be made of 3 1mm wires spaced 3cm 
apart. The center wire forms 20m dipole and is fed with the coax. The 
support is fiberglass telescopic mast 12 meters tall. Very light weight but 
unable to carry much load.
The idea of two chokes came to me as well (one at the feed point and one at 
the bottom. The problem is that the coax shield from the feed point down to 
the bottom of the mast is going to be longer then 1/4 wavelength on 20m and 
close to half wavelength on 15m. This coax will be too close to all the 3 
lower halves of the radiator and will probably therefore detune all the 3 
bands. I will try it within the next few days to see how much harm coax 
does.

73, Igor UA9CDC

> de WB2CPN
> Since it's a coaxial dipole, I would run the coax up
> through the bottom half, and put a good choke on the
> coax where it comes out of the sleive at the bottom.
> It would even be better if he could run the coax down
> inside the support pipe or whatever.   What was the
> question?
> 73  Clete
>
>
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