[Antennas] Feeding vertical triband dipole

[Igor Sokolov]

Hi Alex,
I agree this is easy solution. But I need a portable antenna and I need it 
for 3 bands. Besides fiberglass does not mind to be set in salt water. 
Aluminium does not like it. I am afraid this is not a solution for my case.

73, Igor UA9CDC

> ...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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