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Re: [TowerTalk] 3/4 WAVE PHASING LINES

To: "jimlux" <jimlux@earthlink.net>, "dave arruzza" <w1ctn@yahoo.com>
Subject: Re: [TowerTalk] 3/4 WAVE PHASING LINES
From: "Gene Fuller" <w2lu@rochester.rr.com>
Date: Mon, 8 Nov 2010 10:30:59 -0500
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Your last sentence is exactlty why I try to everything that is under  my 
sontrol as right as possible.   Gene / W2LU

----- Original Message ----- 
From: "jimlux" <jimlux@earthlink.net>
To: "dave arruzza" <w1ctn@yahoo.com>
Cc: <towertalk@contesting.com>
Sent: Monday, November 08, 2010 9:15 AM
Subject: Re: [TowerTalk] 3/4 WAVE PHASING LINES


> dave arruzza wrote:
>> To all,
>> I am installing a elevated 40 meter 4 square over somewhat marshy New 
>> England soil.
>>
>> My property backs up to a drained 30 acre pond. You can see my QTH on 
>> Google Earth. It's the house before the property with the greenhouses.
>>
>> Base elevation is 20' above ground utilizing 2 -  Rohn 25 tower sections 
>> per element. Elevated ground plane.
>>
>> I wish to use 3/4 wave phasing lines instead of 1/4 wave phasing lines so 
>> I can dress the phasing cables down the tower legs and underground to the 
>> Comtek box.
>>
>> The Comtek manual states to use only 1/4 or 3/4 wave cables and I 
>> understand that.
>>
>> Has anyone observed any determent in using the 3/4 wave cables vs. 1/4 
>> wave cables?
>>
> The real difference is that the phasing will be more narrow band (for a
> given phasing error).  That is, say you cut your cables for 7.1 MHz.  At
> 7 MHz, a quarter wave will be 88.7 degrees, the 3/4 will be 266 degrees.
>  The first, an error of 1.3 degrees, the second, 4 degrees.
>
> Neither is particularly huge.  4 degrees will turn a perfect null into a
> -26dB null.. hardly a crisis.
>
> You'll have bigger phasing errors from differences in the ground under
> the antennas and other component tolerances.
>
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