Topband: Solved: Strange resistance between Beverage ground rods

[Herbert Schoenbohm <herbs@vitelcom.net>]

After more ground rods and buckets of water along with several spider 
wires I learned the hard way to *never8 try to make measurement with a 
DVM.  A cheap VOM gave me the results I was looking for.  Now I measure 
45 ohms from the detached reversible Beverage wires out to the end and 
though the reflection transformer and back thorough the ground for 900' 
feet!  Now I am worried that the resistance is to low and the ground 
conductivity over which the Beverage runs is to low.  Measuring several 
Beverages in the shack on this run on BC stations show excellent FB and 
VSWR of 1.5 to 1.
My problem here was a false reading of resistance using DVM's and having 
some residual induced DC voltage making the readings completely invalid.
Thanks to all with there good suggestions.

Herb, KV4FZ



On 11/16/2016 6:55 PM, Mike Waters wrote:
> Good answer, Greg. DC is certainly not the best way to measure an RF ground.
>
> I wonder what the difference would be if we used 1.8 MHz instead of 100 Hz?
>
> I thoroughly soak the earth around the rods here with Epsom salt (magnesium
> sulfate). It *really* decreases the ground resistance! The difference
> between a newly-driven-in rod, and after applying that treatment, is
> immediately obvious by listening to the receiver.
>
> Of course, as N3OX once quipped, "I'm fond of adding elemental copper in
> thin filaments stretching radially away from the ground rod for some
> distance". ;-)
>
> 73 Mike
> www.w0btu.com
>
> On Nov 15, 2016 10:16 AM, "Greg - ZL3IX" <zl3ix@inet.net.nz> wrote:
> > I came across this problem when I first started using Beverages in 2008.
> I have come to the conclusion that the DC resistance measurement is
> corrupted by electrochemical effects between the grounds, ie potential
> differences. I then changed to an AC measurement. I made a simple 100-or-so
> Hz oscillator using an op amp and  I put this between the two wires in
> parallel at the feed and the ground. There is a 100 ohm resistor in series.
> I measure the AC voltage across the Bev and the voltage across the resistor
> and thus deduce a loop resistance through the ground.
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