[Antennas] Diminishing Returns

[Michael Baker]

Hello David,

	I have been just sitting back and lurking but I thought I might just
toss in my 2 cents worth to the mix.
	Think about a mobile whip for HF.
	Not much for "Radials" is there.  Mass of metal is more like it.
They basically use the car body and frame as a large "counterpoise" or
capacitor to COUPLE TO EARTH GROUND.  This is ALSO what your "radial" field
is doing. 

	The one thing all the "experts" will agree on is that you can only
do what you can do for your specific installation.  If you only have about
20 feet of area for ground radials (counterpoise) then put in radials that
FIT in the area you have. IN THE GROUND THEY DO NOT HAVE TO BE A DEFINED
LENGTH TO WORK, THEY JUST HAVE TO BE AS MANY AS YOU CAN PHYSICALLY AND $$$
AFFORD TO INSTALL so you can more efficiently couple to earth ground. 

	My example. 
	I live in the city and have a back yard that is about 70' long East
and West and 25' North and South.  I have a 6BTV Hustler trap vertical
installed about 12' from the West wall of my fence and centered N/S.  Not a
lot of room for a ground mounted set of wires, BUT you put in what you have
that will fit and live with the results. There is NO Point in agonizing over
what would be the "perfect" system IF YOU CAN'T INTSTALL IT anyway!

	The more you can put into the ground counterpoise system the more
efficient you vertical becomes because more of your signal is being radiated
and not heating up the ground. It raises your "radiation resistance".
 
	In FL you have the advantage of the soil being damp and fairly
conductive so you might not see as big a change as I might living in AZ
where the soil more closely resembles decomposed granite and is dry. (What a
concept, you would think it's a Desert!)
	Here in Arizona you MUST have as much wire in the ground as you can
get OR install the vertical in the air with 4, 1/4 wave radials for each
band. When that is done you now have a GROUND PLANE antenna.

	A small footnote here: Install a large value resistor (100K to 500K
Ohms, NON INDUCTIVE) between the vertical and your safety ground at the coax
connection and it will help purge off the static. It makes for a slightly
more quiet install.

	Best 72, 73

	Headed for the yard to finish putting my vertical back together. 
		

Michael Baker  K7DD
k7dd at cox.net

-----Original Message-----
From: antennas-bounces at mailman.qth.net
[mailto:antennas-bounces at mailman.qth.net] On Behalf Of David C. Hallam
Sent: Thursday, June 04, 2009 1:53 PM
To: Merv Stump
Cc: 'Antennas'
Subject: Re: [Antennas] Diminishing Returns

To amplify a bit on my radial problem.  I have the usual 1/4 acre city 
lot.  On this lot there are 7 medium size Live Oak trees.  On the lot 
line adjoining my neighbor there are 4 more.  The only place I have to 
put the vertical is an area between the house and the lot line.  This 
area is approximately 95x20.  The antenna is placed approximately 65 ft 
back on this strip.  The radials will have to run in two pie shaped 
wedges about 180 degrees apart.  The maximum I can get at the end of the 
wedge is about 20 ft.

 From the replies I have received, I gather I am wasting my time putting 
radials down.  I have put in two 8 ft ground rods.  I guess I will just 
go with that.  Because of trees and overhead wiring, I can not elevate 
the antenna.  Living in coastal FL I do not want to roof mount anything.

David
KC2JD/2

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