TenTec
[Top] [All Lists]

Re: [TenTec] vertical dipoles

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] vertical dipoles
From: Ken Brown <ken.d.brown@verizon.net>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Mon, 11 Jul 2005 18:53:38 -1000
List-post: <mailto:tentec@contesting.com>
With respect to the Cebik article:

I agree that this is excellent information. However there is not much 
discussion about feedline current balance, and the effect of the ground 
being much closer to one end of the antenna than the other. The only 
reason given for the ten foot height above ground of the bottom end of 
the antenna, was for safety, keeping the high voltage at the end away 
from people. Surely the greater capacitance to ground of the lower end 
of the antenna is going to have some effect on the current balance, and 
the currents in the two wires of the feeder will not be equal and 
opposite. While I doubt it's a problem, that is where this discussion 
started, as someone claimed excessive radiation from open wire feeder.

Feedlines with equal and opposite RF currents in their two conductors 
(either open wire or coax) don't radiate. Getting the currents to be 
equal and opposite requires care. In the absence of nearby objects, it 
would seem to me easier to accomplish this with a horizontal dipole. 
Orienting the dipole vertically seems like a way to guarantee that the 
currents will not be equal.

Then again, how often are we luck enough to be able to put up a 
horizontal dipole that does not have one leg closer to a tin roofed 
building or metal pole or tower than the other leg.

None of this would keep me from building whichever version, vertical or 
horizontal, fits the space available. I have always found ways to 
mitigate RF in the shack problems. I don't transmit on TV channel 
frequencies (at least not at a significant power level) so if my 
radiating feedline makes someones TV set have problems, I guess there is 
a problem with the TV.

DE N6KB

> Anyone interested in more information about vertical dipoles should 
> take a look at what Cebik has to say.  As always, he has excellent 
> information that is accurate and to the point:
>
> http://www.cebik.com/gp/v20.html
>


_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec

<Prev in Thread] Current Thread [Next in Thread>