[TowerTalk] phased vertical feedpoint question

[Jim Lux]

On 11/7/11 6:07 AM, n8de at thepoint.net wrote:
> Not if the coax shield is grounded at the antenna end.

>
> Quoting Alan Swinger<awswinger at earthlink.net>:
>
>> Figure as part of the vertical length.
>>
>> -----Original Message-----
>>> From: WW3S<ww3s at zoominternet.net>
>>> Sent: Nov 6, 2011 10:36 PM
>>> To: towertalk at contesting.com
>>> Subject: [TowerTalk] phased vertical feedpoint question
>>>
>>> Planning on phasing 2 40m verticals....using Dx Engineering radial plates
>>> with bulkhead connectors and their 19" coax pigtail....should I figure the
>>> 19 inch length into the phasing line calculations?


What kind of phasing scheme are you using? Christman (two carefully cut 
lengths of coax with a T)? Some sort of lumped network? Fixed 90 degrees 
or 180 degrees or what? And how deep a null are you looking for?

Let's say you're looking at 1/4 wavelength, or about 10m (free space).. 
call it 30 odd feet of coax.  Adding 2 feet is about 24 degrees.

A huge phasing error doesn't make much difference in forward gain (24 
degrees is less than half a dB), but might degrade your F/B to -10dB or 
worse.


I'd also think that other factors might actually dominate over the 
length of the feedline. Are these two verticals out in the middle of a 
very uniform field with identical ground radial networks.

WHat I would do is just try it and see, either way.

What you could do is cut some jumpers that are 18" long, and put them in 
and take them out, and see if the performance improves.