[TowerTalk] Vertical dipoles

[Jim Brown]

On Tue, 17 Nov 2009 11:43:29 -0600, Michael Goins wrote:

>Good information, but not necessarily for a regular vertical 
dipole
>center-fed with coax or feeders

Michael,

This IS a "regular vertical dipole," it behaves exactly the same 
as if it were a horizontal dipole and coax turned on its side, 
except that it needs only one support, not two. Rudy's solution, 
and my variation on it, turn the outside of the coax into the 
bottom half of the dipole. 

Your concept -- a horizontal dipole turned on its side with coax 
coming off at right angles to it is not only difficult to rig, but 
it also requires a very robust common mode choke (coax wound 
multiple turns around a ferrite toroid) to prevent the coax from 
interacting with the dipole. The elegance of N6LF's solution, and 
of my variation on it, is that 1) a single support point is 
required; and 2) the choke is the end insulator of the antenna. 

BTW -- as I've observed in that tutorial, a vertical dipole is not 
a very good antenna, primarily because reflections from ground 
give it a rather poor vertical pattern. :) This is clear from the 
NEC model, and on-the-air tests yield the same result. The 
vertical works, but an inverted Vee hung at the same height from 
the same support works a LOT better. 

73,

Jim K9YC