TREAD lightly as well... (Bill)
as for 'how close' someone had asked.... when I model a HiZ 4 element RX
array I can move one of my towers as much as 500' away and it STILL has a
noticeable impact on the FB! One has to remember at 160 and even at 80
distances are getting up there...
Gary
-----Original Message-----
From: StellarCAT
Sent: Thursday, September 22, 2016 6:07 PM
To: TOWERTALK@contesting.com
Subject: Re: [TowerTalk] 4 square for 80
Hey Bill! Been a while - glad things are progressing back out in KH land ...
First I'd say what K3LR says is good advice - I can't contest it - just he's
had many years of experience and experimentation ... also the bit I've read
in the LB DX book suggests it is the case as well. I do know after having
done some modeling with a center tower that it is a real pita ... I will
also have a rotating tower (currently have 64' and one ring up - hope to
have it completed in a month) ... my plan for 80 is to use a rotating dipole
at 143' at the top of the tower. I had this in AZ and it worked extremely
well even against 4 sqs ... also I've modeled it and have confirmed this.
Note one thing that gets in to the mix when comparing it to verticals is the
quality of the ground. Here, at least according to all the data I can find
(which all agrees) my soil is quite poor - and thus the dipole does very
well against a 4 sq except at very low angles ... so even if you can't do a
rotary dipole do consider and model the ground re verticals.
Can you put the verticals on the ground - i.e. no elevated radials?
And what is the issue of isolating the tower? I understood this consists of
an arm that runs along the tower - spaced maybe 1/2 meter away and something
like 5 meters long, with a series cap to tune it out on 80 meters. If the
feedlines are run inside the tower they are not as much of an issue... that
all stated I decided it wasn't worth all the experimenting to make it work.
There's no way to get good quantitative results - you end up always thinking
"it justn't doesn't FEEL right" (like you had said in another post re your 8
element RX array being near a tree) ...
I had thought about a 100' R25 tower with top loading for 160 - the top
loading coming off then supporting a 4 square for 80 ... but when I model
this I have to go down to something like 40' lengths for the tower
insulating it at the base and twice more up the tower with relays to shunt
around it to 'eliminate' it ... and from lots of modeling I can say that
'eliminate' is a poor word - no matter how non-resonant it is it WILL have
current induced in it and that will impact the FB - often considerably. So
trend lightly my friend!
Gary
K9RX
now in Piedmont, SC
-----Original Message-----
From: cqtestk4xs@aol.com
Sent: Thursday, September 22, 2016 3:59 PM
To: TOWERTALK@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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