Topband: Response to W8JI's comments about using a K2AVfoldedcounterpoise at VK6VZ

[ZR]

>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