Hi Herb,
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.
I have been doing this measurement once a month ever since, irrespective
of whether I think the performance on 160m has changed or not.
73, Greg, ZL3IX
On 2016-11-16 03:20 a.m., Herbert Schoenbohm wrote:
I have reflection transformers at the end of every two wire Beverages
which I try to test by measuring the wires on the feed end. I remove
the transformer from the two wire WD1-A and check the resistance
between the two wires which tells me that through the reflection
transformer I have continuity. It measures about 40 ohms wire to wire,
this is done when I notice any performance change of the antenna. Now
come the next test that baffles me completely. When I measure from
either wire to my ground rods alone, to see what the return resistance
is, I get reading in the vicinity of 20K across the 900 foot run.
I understand that if the reading was very low it would defeat the
whole Beverage principle. But is 20K Ohms reasonable, very good, or
marginal? I use three foot foot rods at either end and when I pull
one out yesterday before moving it the bottom 1/4 was moist and muddy.
That Southern end of several reversible Beverages is located about
100 feet or less from a salt marsh or salt pond. I also have to such
antennas made up of ladder line a DX Engineering components. They all
appear to be working well even though large grass has reach and
covered portion of some of them.
But my question is what is a reasonable or good return ground
resistance for a 600' or 900' Beverage. I haven't found any sources
of information expect the saying that the higher Resistance the
better. Is this correct?
Herb Schoenbohm, KV4FZ
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