[TowerTalk] K9LT/K3LR Lazy Vee Array - rigging question

[Gene Fuller]

Hi Pete -

I was not aware of the QST article but at about that about time, after some 
modeling I morphed my three element sloping dipole array into what I call a 
three bent vertical dipole array. I have found it to be very much worth the 
minimal effort. According to the modeling, it's good for 3 or 4 db gain, but 
more importantly it lowers the radiation angle from 25-30 degrees sown to 
just under 20 - great for 80 meters.

Relative to you comments/questions. If I get the picture correctly it sounds 
like you would be using the guys to support at least the top half of the 
dipole. I don't think that would lift the feed  point high enough, resulting 
in the bottom halves crossing at the base of the tower. Probably not 
terrible serious, but certainly not most desirable.

To those with sloping dipole arrays, I would highly recommend  recommend 
converting them to "bent vertical" dipoles. Just put a rope from the center 
insulator out to where the bottom half of the dipole ends, possibly out just 
a little further out to account for sag, and then bring the bottom half of 
the dipole back to the tower base. this results in canceling most of the 
horizontal radiation and gives you a good efficient low angle vertical 
radiator without the need for radials. Use three of these (at 120 degree 
spacing). Feed one at a time and leave about 5/8 wave of open  (shield must 
also float - DPDT relays) feeder on the unused dipoles.  The unused dipoles 
then look like reflectors and give 10-20 db F/B. The patterns are about 120 
degrees wide so you get quite good azimuth coverage with just three. About 
the only shortcoming I find is that the forward vertical aperture is quite 
wide, letting in more noise than a good straight vertical. Otherwise, from a 
forward gain standpoint, it comes very close to a four square, without 
needing the radials. But, yes, it does require a fairly high tower.

Gene / W2LU
----- Original Message ----- 
From: "Pete Smith N4ZR" <pete.n4zr at gmail.com>
To: "TowerTalk" <TowerTalk at contesting.com>
Sent: Tuesday, August 21, 2012 4:38 PM
Subject: [TowerTalk] K9LT/K3LR Lazy Vee Array - rigging question


> About 10 years ago, I put up a 4-way lazy vee array for 80 meters,
> suspended from near the top of my 97-foot tower.  It is based on the
> design shown in August 94 QST, which involves 4 dipoles, pulled away
> from the tower by their center insulators, such that the lower leg of
> each dipole can come back to the tower base 6-7 feet above ground.
>
> The only weakness of the design is that it relies on tension to take the
> slump out of the catenary, so that the feedpoint is as high as possible,
> and that requires either a lot of tension or anchor points that are well
> outside the guy circle.
>
> I soon discovered that while the array was definitely directive, three
> directions (the W9LT design) would probably be sufficient, because the
> difference between adjacent directions was usually minimal.  About 7
> years ago, I replaced my top guys with 6700 lb Phillystran, as part of
> installing a second tribander under them. More recently, tree growth and
> wear and tear on the array wires has reduced mine to 3 dipoles anyway,
> and they now are aligned approximately parallel to the guys.
>
> So, I had a bright idea.  Suppose I let all three dipoles down to the
> ground, and then attached some sort of smooth rings to the top insulator
> and to the dipole feedpoint.  These could then be attached so that they
> would slide up the Phillystran guys as I pulled the dipoles back up,
> suspending them, taking the weight off the catenary and letting me
> tether the three dipoles right at the guy anchors.
>
> The one potential downside of this I can see is the possibility that the
> two hangers on each guy might chafe the phillystran's plastic cover and
> eventually cut down into the Kevlar itself.  On the other hand, it
> occurred to me that I could make the suspending loops out of some
> material that is softer than the Phillystran's jacket, so that it would
> not be harmed.  Presumably braided nylon rope, cotton rope or other
> materials might meet this spec.
>
> Has anyone done something like this successfully?  Any advice on 
> materials?
>
> -- 
> 73, Pete N4ZR
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