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Re: Topband: Response to W8JI's comments about using a K2AVfoldedcounter

To: "Tom W8JI" <w8ji@w8ji.com>, "Dan Edward Dba East edwards" <dan.n.edwards@sbcglobal.net>, <topband@contesting.com>
Subject: Re: Topband: Response to W8JI's comments about using a K2AVfoldedcounterpoise at VK6VZ
From: "ZR" <zr@jeremy.mv.com>
Date: Tue, 25 Sep 2012 10:13:23 -0400
List-post: <topband@contesting.com">mailto:topband@contesting.com>

I wonder.....Is there is a simple way to compare the field strength of an FCP with my current NON dense and uniform ground system, and draw reasonably accurate conclusions about efficiency improvements >>>
Sure. You can probably determine ground wave changes in a vertically 
polarized radiator with a simple test, if you wanted to do the work. Since 
you wouldn't know the baseline performance all you really could say is if 
it is better or worse than what you had.
Which brings me back to my general statement that a large change isn't so 
much about how perfect new systems are, as how bad our old systems were. 
:-)
I can tell you from direct experience at my house that near field effects 
on 160 meters were noticeable at 300 feet, were barely noticeable at 600 
feet, and were not measureable at 1500 feet. This was with an instrument 
that resolves 100th's of a dB, and is accurate in tenths over the signal 
level range. This is based on data acquired while attempting to null my 
transmitter out of receive antennas, (bottom of page at 
http://www.w8ji.com/antenna_coupling.htm) but would apply to pattern 
measurements.
This effect was with a large directional transmitting array, so it would 
be reasonable to expect a smaller array to require less distance. Based on 
measurements, 500 feet distance should be pretty safe.
It does not require absolute field intensity measurements if you only want 
to look at change. I primarily use two <$100 instruments here for playing. 
One is a Sierra 303B portable level meter, and the other less portable 
unit is an HP3586C.
I built small loop antennas for the 303B and calibrated them against a 
rental FSM.
I have also used fixed wire antennas that I installed out in the woods 
when I did not need an absolute level.
Having a portable selective level meter is worth it's weight in gold if 
you do antenna work. I use the HP3586C to look at signal levels here in 
the house. This lets me check gain and F/R of various antennas. It is far 
more accurate than spectrum analyzers and S meters. The HP will do 
averages, so it is great for testing transmitting antennas while listening 
to distant signals on them, like using W1AW to compare two transmitting 
antennas on skywave. I think I paid around $50 on eBay for it.
73 Tom

I'll have to agree about the HP-3586. I use mine as far as 750' back from the house since I already have 240V almost halfway back and then run a long extension cord.
It rides in a cart behind the lawn tractor after clearcutting a path to the 
stone wall.
Carl
KM1H


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