[BC] AM Ground Systems & Ground Conductivity

[Milton R. Holladay Jr.]

SC is the same way: conductivities of  2 or 4 shown, but in reality measured
at < than 1 in most places.
It's more likely that longer radials might benefit your signal; ~4/10th
wavelength has been determined to be the point of diminishing returns. Some
might recommend a set of short--50'-additional radials to be added, as for
sandy soil, but where I've seen them used, I couldn't see any benefit.
Aluminum will be almost as attractive to thieves as copper. Copperweld might
be a good alternative, or you could use barbless galvanized if you replace
it every 5 to 10 years.....
Can you say"modification of CP"?
M
----- Original Message ----- 
From: "Bailey, Scott" <sbailey at nespower.com>
To: "Broadcasters' Mailing List" <broadcast at radiolists.net>
Sent: Thursday, December 21, 2006 11:49 AM
Subject: [BC] AM Ground Systems & Ground Conductivity



I have a question for all that's been on my mind. We live in an area
that is rocky, with lots of hills, etc.  The FCC ground conductivity map
says we have a "4" in ground conductivity in this part of TN. Some
engineers and I've even have come to the conclusion that it's worse than
that, more like a 1 or less.

In thoughts of replacing a ground system, I stop and think, and I
realize what the FCC rules say, yes, 120 copper radials, cut at 1/4
length of the frequency, spaced apart every 3 degrees. Yea, yea, we all
know that, but I sit on property that has not much soil and has lots of
limestone under what little soil there is.

My tower is at 150' on 1560, using a 3 fold unipole. What does one
consider in an area of bad to no ground conductivity and here another
issue, my site is in an area of high crime. When I bought the place, I
didn't realize there was no ground system. Found that out later on that
it appeared that it was stolen.

The antenna makes the licensed power at the tower is at the correct
"licensed" impedance, but I wonder in replacement of the ground system
and the station gets out o.k., actually I've been told it gets out there
very good, being on the high part of the band.

My question is if I put down another buried ground system, can I get
away with shorter radials, and use aluminum instead of #6 copper or #12
copper, due to the copper thieves?  Would the FCC give me a wavier on
this?

Scott