Between the two tests you suggest, my vote would go for the later RF test.
I would not assume that a DC test measurement necessarily correlates to
what's occurring at HF when diagnosing a problem.
Good luck and please post what you discover.
73
Matt
KM5VI
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
Eduardo Araujo
Sent: Wednesday, March 06, 2013 4:56 PM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] ground radial problem
Hi Matthew, Bill, Jim and the rest of people who is following this thread.
Most of you are pointing to a corrosion problem and most of you suggested to
go to copper or copper clad. Also another good suggestion was to go to
raised radials specially considering I already have a ground screen below.
Now, before I do the change, I have a couple of ideas to check the actual
radials. One of your suggestions was to dig a little bit, find them and
check them physically.
Besides it occurred to me 2 more methods, one is to measure DC resistance
from each radials separately against the ground rod and the second is to
install just one 1/4 cooper radial lying in the ground, connect it to the
coax braid and measure its current with 10 w, then put one of the actual
radials in parallel of it and measure current distribution between the 2.
That, I think, could give me a clue before changing the system.
Of course I must keep the system adapted for this conditions.
Many thanks for time and suggestions, they were very useful for me.
Eddy, LU2DKT
> -------- Original Message --------
> Dear people, I experience a situation that confused me a
> little bit.
>
> I have a vertical with 60 iron fence wire buried radials 1/4
> wave long plus
> a ground rod. I installed it 2 years ago lying on the ground
> and now they
> are buried.
>
> Prior to the contest I decided to check the buried radials
> of my vertical.
> I have bundles ranging from 4 to 7 radials connected to a
> square ring
> around the base of the tower. I provided 20W input and I
> measured the
> current entering each of the bundles which is a procedure I
> have done many
> times.
>
> To my big surprise there was little to no current entering
> most of the
> bundles except one which also had a ground rod besides the
> radials.
>
> This bundle took aprox 80% of the total current. Then I
> decided to measure
> the current entering the ground road and it was aprox 100%
> of the total for
> that bundle.
>
> This situation was the opposite I always had measured before
> where the
> ground rod practically had insignificant current.
>
> 2 months had passed without any rain so I tried to spread
> some water around
> a radius of 4 meters but situation didn?t change
> dramatically but yes an
> small increase in all radials current
>
> That night I thought a lot of possibilities but the
> strongest one was that
> for some reason most of the radials had dissapeared or at
> least have been
> reduced to short ones.
>
> Next day we have 27mm of rain. Another surprise, everything
> back to normal.
> I had current in all bundles and almost nothing into the
> ground rod.
>
> I expected that having 60 radials it should not matter if it
> rains or not.
> I expected to have a relative good shield of the ground
>
> Question 1: Any guess what could be going on ?
>
> Question 2: Is it a normal situation? Does anyone experience
> the same?
>
> Question 3: Could it be possible that radials could have
> been eaten by the
> soil and I am having very short ones? and that made them so
> much soil
> conductivity dependent?
>
> Question 4: if the soil is so dry why the ground rod collect
> so much
> current from the same soil?
>
> As I have no explanation so far, I am planning to add
> another 60 radials
> and for a reason of cooper cost I am planning to use what I
> think should be
> similar to what I read here many times as WD1. It is for
> exterior telephony
> drop consisting of a pair of 0.8 mm of stiff wire which
> looks like iron
> covered by cooper and both separated by 3mm of a very heavy
> plastic. I
> measured 13 ohms of DC resistance in 60 mts of wire.
>
> My plan is to split the 2 wires and use them as radials.
>
> Question 5: It is a good or a bad idea to use this kind of
> wire instead of
> fence wire?. Cooper will be the last option of course
>
> Many thanks in advance for your opinions.... Eddy, LU2DKT
>
> _______________________________________________
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