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Re: Topband: Half Slopers

Subject: Re: Topband: Half Slopers
From: K4SAV <>
Date: Mon, 04 Feb 2008 22:17:25 -0600
List-post: <>
I have to modify some of my quick answers.

WS6X wrote:
1. Other than the tower itself, exactly which components contribute to the
radiated field? I understand that the minimal contribution of the sloping
wire is high angle radiation, but what about the yagis used for top loading?
Do they actually radiate?

WS6X  wrote:
Theoretically, no.

I answered this question a little too quickly and without details.  The 
Yagis don't contribute any significant radiation to the total if they 
are symmetrical (most of the fields cancel).  They mostly act like top 
loading for the mast and tower which is the part that radiates the most, 
but they are a very important part of the antenna, and there are 
currents in the Yagis. 

WS6X wrote:
3. I understand how to decouple or detune a classic shunt-fed tower for use
with a nearby RX antenna. How would you best detune a tower-fed half sloper?
I could easily switch in additional length to the bottom end of the sloping
wire, or switch in a reactive component at the tower feedpoint. Would this
do it?
WS6X  wrote:
You could switch it out at the feedpoint with a relay or detune it by 
lengthening or shortening the sloper wire.

Correct again Jim.  I was thinking he was asking if a different length 
sloping wire would do it.  Well no, not if it's there all the time, but 
if it is switched when changing from transmit to receive that would do 
it, provided the tower by itself is not resonant.  I would first try to 
find a method that doesn't require a T/R relay.

Jerry, K4SAV

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