[Antennas] Vertical and parasitic question

[mstump at hvc.rr.com]

Alan, I have made several attempts at this and have never been successful.  I have found it much easier to put up two quarterwave verticals of equal length spaced 1/4 wave apart and feed them 90 degrees out of phase.  There are several commercial products on the market which accomplish the phasing and matching (ComTek in my opinion being the best); but the simplest way is simply to feed the two verticals with equal lengths of coax and then add an electrical quarter wave of coax to one or the other.  I have always added this quarter wave inside the shack so I could switch it from one to the other.  The system is directive in the direction of the phase lag, meaning the vertical with the extra coax is the front and the other is the back.  

John Devoldere's book, "Low-band DXing" provides good detail on this system.

Regards, Merv, W2OE

----- Original Message -----
From: ARDUJENSKI at aol.com
Date: Tuesday, August 24, 2004 10:54 pm
Subject: [Antennas] Vertical and parasitic question

> When setting up a 1/4wl vertical with a director or reflector 
> element  what 
> is the best way to get them adjusted? I assume there is going to 
> be a  
> compromise between gain and F/B ratio.
> 
> For example my guestimate and rough run on EXNEC shows a target 
> set up  of:
> DRIVEN ELEMENT 33.4ft
> DIRECTOR: 32.5ft
> SPACING: 15ft
> GAIN: 4.dBi
> F/B 12dB
> FEEDPOINT: about 15 ohms
> 
> When you actually set this up in the field how do you tune for 
> best  
> performance in the field? Do you recommend setting say both 
> elements at 34ft and  use 
> base variable capacitors to electronically adjust the element 
> lengths say  for 
> 7.1 and 7.45 MHz (5 percent shorter so use 5 percent higher freq)? 
> Or just  
> set them up us as guestimated above? Then what?
> 
> I have looked in several sources and searched the web with no 
> success. I  
> would appreciate any guidance or point me to a good reference.
> 
> ( I figure mutual conductance and varying ground conditons will 
> play a role  
> in tuning for best performance).
> 
> Thank you
> Alan KB7MBI
> Woodinville, WA
> - - - 
> 
> Your moderator for this list is:
> Larry Wilson KE1HZ antennas-owner at mailman.qth.net
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