R: [TowerTalk] Insulating tower

[Maurizio Panicara]

A 75ft tower is a too short radiator for a gamma match.
An omega match could do it but won't fix inherent antenna losses, due 
to a low Rr, and ground losses.
Also a linear loading won't improve antenna performances and an extra 
device for matching to 50 Ohms will be required.
Best solution is probably to add enough capacitive top loading (useful 
to rise Rr and efficiency) so electrically lenghtening the antenna 
until a gamma match can be used.
The top loading can be in the form of some sloping copper wires of
appropriate length.

Generally speaking, a 4 square is not such an easy array to make 
working properly, expecially when antennas are tightly coupled and 
short.
In my experience I've rarely seen 4 square arrays with a real and
substantial gain over a symple 2 phased array.
I got convinced this is because of ground planes that do not have proper
characteristics to satisfy the 4 square needs.
With short radiators ground plane is never good enough and often the 4
square gain is only marginal.
With not resonant short verticals a better gain is often obtained 
focusing on a single element (making it longer, either phiscally and 
electrically) and minimizing the ground losses than phasing multiple 
antennas with an insufficient/improper ground plane.

73,
Mauri I4JMY



----- Original Message ----- 
From: Major Ron <majrabsr@rconnect.com>
To: towertalk <towertalk@contesting.com>
Sent: Tuesday, April 04, 2000 3:16 AM
Subject: [TowerTalk] Insulating tower


> 
> Hi Guys,
> 
> I've been reading this newsgroup for a couple months and have been =
> really impressed with the knowledge available.
> 
> I recently acquired and moved to 20 acres in SW MN. Now have about 5 =
> acres for antennas.
> 
> I want to build a 4-square array for 160M. Already have 4ea 60-ft Rohn =
> 20 towers and 4ea R/S 19-ft telesoping masts, which will be attached to =
> the towers for 75-ft total height.
> 
> Now the problem: How can I insulate the towers from ground?
> 
> I need a CHEAP solution.
> 
> Tnx & 73,
> Ron, KA9ALC
> 
> 
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