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[TowerTalk] Advice on 2 el 40M Vertical Array

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Subject: [TowerTalk] Advice on 2 el 40M Vertical Array
From: (Bud Semon N7CW)
Date: Wed, 16 Jan 2002 18:17:18 -0800
I'm looking for a small improvement in my 40M signal and have the following 
thoughts and constraints.  I'm currently using an 80/40M trapped vertical 
(similar to the BattleCreek Special, without the 160M section) over a limited 
set of radials.   The yard is fairly small and 80M radials can only cover one 
90 degree quadrant.

For the moment, I will do without 80M.  I can squeeze in 2 40M verticals with 
1/4 wave spacing, but the radials would only cover about 270 degrees around 
each vertical.  If I use 1/8 wave spacing, I can pretty much cover 360 degrees.

Since I am mostly a DXer, with limited contesting and my location is in San 
Diego, the most important directions for me are NE and SW, which is convenient 
for locating the verticals.  I haven't seen a way to phase 1/8 wave verticals 
for a broadside pattern, but I don't really care too much about those 
directions.  Also, being in the most southwestern corner of the country, I have 
no QRM from the SW when I point NE (the ocean is out there) and little QRM from 
the NE when I point SW (this is the LP and the sun is up to the east of me). 
 Consequently, I think working hard for the last couple of dB of F/B is not 
worth it.

So....looking through ON4UN's book, the 1/8 wave spaced array with the 
Christman coax feed method seems like a good fit.  Does anyone have a better 

I also have a couple of specific questions.  Are the impedance measurements I 
can make with the MFJ259 accurate enough for proper phasing calculations 
(including the mutual impedance)?  For radials that run between the 2 
verticals, should I terminate them in a ground line that bisects the verticals?

Thanks in advance for any thoughts and 73,  Bud  N7CW

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