[TowerTalk] V beam leg lengths

[Al Williams]

I had a 50 foot v beam up at about 70 feet for several years but finally 
took it down because my triband yagi perforned better (except 40m). Its apex 
angle was fixed at about 50 degrees. That apex angle was selected as a 
compromise from a graph in an older ARRL antenna book.

I took the vee beam down after I modeled it with EZNEC and learned how the 
apex angle effects the maximum gain (vs broad beam).

I have thought of putting up several wires and selectng the apex angle with 
relays like you are designing. However to get a gain better than a simple 
Yagi requires a pretty narrow apex angle which means  a lot of wires and 
relays ( if you want to steer the direction).

I dont understand what your design of the "enclosed angle ...is about 30-35 
degrees  ...for a correct apex angle.." means?

I urge you to model your proposed design.

k7puc


----- Original Message ----- 
From: "Chuck Gerarden" <cgerarden at atomix.com>
To: <towertalk at contesting.com>
Sent: Saturday, April 10, 2010 8:27 PM
Subject: [TowerTalk] V beam leg lengths


>I am designing a V beam system with 4 legs radiating out from my 80
> meter tower, parallel to the ground. any 2 of the 4 wires can be selected
> by relays for correct apex angle based on frequency. I am trying to
> avoid any interaction with the 80 meter horizontal phased array at 100
> feet. V legs are at 70 feet. I am trying to avoid leg lengths that are
> near 1/2 waves on 80 and have come to a compromise of 500 feet. My 500
> feet was determined by multiplying 3 - 1/2 (140)waves and adding a 1/4
> (70)wave. Antenna is fed with 450 ohm line and balanced tuner.  I intend
> to use the V beam mostly on 40,20,15,and 10. The enclosed angle between
> the wires is about 30-35 degrees. Does anyone have suggestions on best
> wire length to avoid 80 meter interaction? Any empirical input to this
> project is appreciated. . I also refer everyone to the Aug 1956 QST
> article on multiple V beams.
>
> Thanks, Chuck, W0DLE
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