[TowerTalk] 4 square for 80

Thu Sep 22 17:30:47 EDT 2016

Hi Tim,
IMHO this topic is of great interest to many hams. As you can imagine what Bill is trying to accomplish is quite appealing, just to name two:
1) Why build standalone elements if you can use the tower?2) Why deal with zillions of ground radials if you can have them on the ground?
I have been planning of using wire verticals suspended off the tower too and feeding them with the DXE phasing box.
So I think it will be incredibly useful if you share your engineering work, DOs and DON'Ts, etc. with the community, either via the DXE site or the 2017 edition of CTU. I have spent days going thru the various antenna books and while the issues you raise are mentioned the solutions are light on details. For example, simple question- how would I know if my 90' tower loaded with a bunch of yagis will or will not impact the array? If it does, how far away should the array be?
Just a thought.
Rudy N2WQ      From: Tim Duffy <k3lr at k3lr.com>
 To: cqtestk4xs at aol.com; towertalk at contesting.com 
 Sent: Thursday, September 22, 2016 5:12 PM
 Subject: Re: [TowerTalk] 4 square for 80

Hello Bill,

I want to clarify some of your notes below, as many guys are reading your
post and might be confused. We need to insure we get this right.

T top elements (loaded) will not have a feedpoint impedance of 36 ohms +/-
j0. The hybrid coupler four square boxes are predicated on FULL size 1/4
wavelength elements - so DXE does not recommend using loaded elements. The
system will not work properly.

I listened to your call with Rod, K8AAV here at DXE to make sure we have
this right. Rod said that you SHOULD NOT use raised radials as they are hard
to get working correctly. They MUST be tuned to work and there is a process
for this. You also need to install chokes when using elevated RG-11 feed
lines at the element feedpoints and at the Comtek box; otherwise there is
significant pattern distortion. They can work - but it takes lots of
patience and we recommend traditional ground mounted radial systems for best
performance.

The tower in the middle of your 4 square will interact with your proposed
system. How much or how little depends on many factors. Rod reviewed the
detuning approach with you - which is almost impossible for you to install
with a rotating tower.

Having engineered 4 square antenna systems (successfully) for over 25 years
- I was the advising engineer to Rod on your project. I was very careful to
make sure Rod had all of his facts correct before giving you advice.

You asked for advice on your project and we gave you the straight engineered
scoop - with tons of experience. We do not want you to go through lots of
work only to find out a system you proposed does not work correctly. You
might get various other guidance from others, my advice is be careful.

Trying to make everything work properly on one tower like this is very hard
and there is no free lunch. Only properly engineered systems have a high
probability of working correctly.

Please feel free to call or email me directly to discuss your options.

Very 73,
Tim K3LR

-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Bill
via TowerTalk
Sent: Thursday, September 22, 2016 4:00 PM
To: TOWERTALK at contesting.com
Subject: [TowerTalk] 4 square for 80

This will be my first foray into the world of 4 square xmit antennas.

Plans are to make the elements from wire, suspended from the tower by rope
at about 80 feet.  Due to the slope of the ropes from the tower to the
ground, the elements might wind up a little short.  Plans were to T-top them
running the wire parallel to the rope.  The elements might be around 60 feet
so it would not be that hard to T top them to make up the extra length
needed for 1/4 wave.

I had planned to do the following:  Have an elevated ground system a 1/4
wave radials running from the base of each vertical.  Height of the system
would be 10 feet.  Radial system would consist of 16 radials for each
vertical using the Comtek 4 square system to control it.

In talking with the guys at DX Engineering about the planned setup I was
given the not so good news.

First, I was told you CAN NOT use an elevated ground system with the 4
square.

Second, I was told the tower would interfere with the system.  They said I
would have to cage the tower to make it "invisible" to the system.  Caging
the tower is impossible since it is a rotating tower and the cage would wrap
on the stacks mounted on the tower.

Was he right about all of this?

I can not put up another tower due to tower restrictions (one tower
allowed), so the only way I can get enough height to suspend the wires is to
use the tower I have.  The county thinks anything 60 feet high constitutes
another tower, so I can't make aluminum verticals.  No trees around either
for supports.

I really am in a bind for 80 if all this is true.  An inverted Vee  at 80
feet is far inferior to the 4 square I had planned.

Ideas and thoughts on this?

Bill K4XS/KH7XS
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