[BC] Counterpoise Ground System

[Bailey, Scott]

You mean to tell me someone can use uninsulated, stranded, copper wire?
Wouldn't it stretch, and the weather would get to it too?

I knew an old engineer that was working on a old, broken down AM
facility out in Oklahoma, and he had used aluminum in a pinch for some
kind of ground system. He said it worked, but I had my doubts.

-----Original Message-----
From: broadcast-bounces at radiolists.net
[mailto:broadcast-bounces at radiolists.net] On Behalf Of Cowboy
Sent: Tuesday, September 19, 2006 2:32 PM
To: Broadcasters' Mailing List
Subject: Re: [BC] Counterpoise Ground System

On Tuesday 19 September 2006 11:35 am, Bailey, Scott wrote:
> Willie,
>    How far did your wires go out from the reference tower? 

 The further, the better, with diminishing returns.
 Since the high current is in close proximity to the tower, that's
 where the greatest benefit will be, decreasing to near none 
 at the far ends.
 Most go 20 feet or so.

>    It appeared 
> that the wires were insulated copper, is that o.k. to use?

 The RF field doesn't care.
 There is no technical reason whatever to use uninsulated wire, either
 for an elevated counterpoise, or a buried one.
 ( with no effort at all I can think of many advantages to burying
insulated
 wire instead of uninsulated, and stranded as well )

On Tuesday 19 September 2006 11:56 am, Bailey, Scott wrote:
> Hey Willie, 
>    Thanks, that's what I needed to know.  I'm looking into using
> copperweld, instead of bare copper. As Ron Nott put it, Copperweld has
> no value to the drug lords, and does just as well as say a #10 or #6
> solid copper wire.

 It's about skin effect, so copper weld should be as good as soft drawn
copper.
 That won't stop 'em from stealing it, though.
 The thieves won't know it's worthless until you have several thousand
dollars
 in damage already done.
 #10 is convention. Take your base current divided by 120, and you'll
have a
 rough idea of the near ( maximum ) current in each radial. 20 guage is
plenty
 big enough, but unconventional ( cowboy engineering ? ) so not widely
accepted,
 and MUCH more fragile.
 The big reason for #10 if the fragility of smaller wire.
 ( unless you are a low Z tower blowtorch with 75 amps base current )
 (( come to think of it, even if you are, 20 guage is still big enough
))

 Measurements done many decades ago suggest that 6 elevated 1/4 wave
wires
 will produce the same field as 120 buried wires. 
 It's ALL about eliminating the lossy dirt from the field. 
 If you're not putting energy into warming up the dirt between the
radials, you
 have that much more to go into radiated signal.

 If you already have a conventional buried system, there is no practical
( or
 economical ) advantage to building an elevated ground system.
 If you do not, or for whatever reason can not, do a conventional buried
system,
 then I might look at an elevated system. It WILL be a maintenance
headache.
 You would be much better served by installing an expanded mesh ground
screen
 in the close proximity to the tower, out as far as you care to afford,
also buried and
 bonded to the radial system. The farther out you go, the better, with
diminishing returns.
 It gets much more expensive further out, as the return on investment
approaches zero
 at the far ends of where your radials already are.
 Since the stuff comes in 8 foot rolls, 24x24 is typical. Larger in
multiples of 8 feet.
 32x32 is slightly better, but MUCH more expensive.
 50 foot interspersed radials is a cheaper approximation of a screen. 

 I found a company out of Cleveland that will do VERY large copper weld
screens for
 a client, but that client still owes me about $8K ( Kevin Kidd consider
yourself lucky )
 so didn't persue that approach, but the possibilities are
interesting.....

-- 
Cowboy

_______________________________________________

The BROADCAST [BC] list is sponsored by SystemsStore On-Line Sales
Cable-Connectors-Blocks-Racks-Wire Management-Test Gear-Tools and More! 
www.SystemsStore.com       Tel: 407-656-3719    Sales at SystemsStore.com