[TowerTalk] 3/4 WAVE PHASING LINES
w2lu at rochester.rr.com
Mon Nov 8 07:30:59 PST 2010
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 at earthlink.net>
To: "dave arruzza" <w1ctn at yahoo.com>
Cc: <towertalk at 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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