[TowerTalk] [Bulk] Re: RF Ground is a Myth

[Roger (K8RI) on TT]

On 1/21/2015 1:53 PM, Jim Brown wrote:
> On Wed,1/21/2015 6:57 AM, Roger (K8RI) on TT wrote:
>> It has been my experience that "Mother Earth" does not supply a very 
>> low resistance path, even with a large grounding system of multiple 
>> ground rods and lots of, large, bare Copper wire.  Much depends on 
>> your soil conditions, but do not be disheartened if you see more than 
>> 1 or two ohms. Others may have had different results. 
>
> Right. The earth is a big resistor whose conductivity varies widely 
> from one place to another. I've measured in the range of 50 ohms 
> between two 8 ft copper clad steel rods about 12 ft apart, driven with 
> only an inch showing. This was at the base of my big tower. This was 
> with a DC VOM. As Jim Lux noted, not an ideal method.

I've mentioned this before, bit I think it's relevant to this discussion.

When I lived a mile S of Breckenridge, MI My station was in the 
basement.  The station ground was just on the other side of the basement 
wall(Maybe 8 feet of copper wire to the ground.  The house service 
ground was about 50 feet straight West.  About 75 feet straight W of 
that was my 40 Meter 1/4 wave vertical with a ground rod under ir.  
there were only 4 bare copper radial (slightly over a 1/4 wave long)  So 
essentially the station had two ground rods tied to the station ground. 
Rephrased, the station has two grounds in parallel about 50 feet from 
the service ground.

The photos in http://www.rogerhalstead.com/ham_files/boatanch.htm came 
some years after the 101B , but it was located pretty much in the same 
place as the KWM2 and Ten Tech stations which were not grounded/earthed 
a whole lot better, but the electrical system did tie the neutral back 
into the panel grounds.<:-))

The exciter was a Yaesu FT-101B.  The Yaesu power cord was a two 
conductor cord with a two pin, polarized plug.
The cord connected to the exciter through a 4 pin Jones plug and socket 
with the male end mounted on the chassis.  Inside the chassis the Jones 
connector had to  wires of about #10 soldered to the connector with a 
very generous  amount of solder.  It was a very nice looking solder 
joint even with the generous amount of solder. The only problem was that 
with a little side pressure on the power cord, tht generous solder joint 
could make contact with the chassis.  Now the neu8tral "SHOULD" have 
tied to ground in "the panel", but apparently it did not.  As there was 
no ground wire to the exciter e4xcept the station ground. Ground was 
through two 8' ground rods through about 50 feet of wet soil to the 
service entrance ground.

The problem with the station ground ans lack of continuity of neutral to 
ground was not known to me at the time, but I was getting very close to 
discovering it!

The radials for that 40 meter vertical just kay in the ground. They had 
a 90 degree bend aboit5 8 to 12 inches from the end,  The radials were 
pulled tight and held by that piece stuck in the ground which made sense 
at th time.  The radial to the S had come loose, so I  pulled it tight 
and knelt down to stick the end back in the ground.  THAR was when I 
discovered the problem!  When my knees touched the wet soil, "it had 
me"!  My muscles tightened up and I had a really good grip on the wire. 
Almost as good a grip as it had on me.  Fortunately my weight was not 
centered and I(* fell over backwards.  As soon as mu knees broke 
electrical contact with the wet yard it let go of me and I had enough 
sense left to throw that bare copper wire  before I hit the wet ground.  
My arms, legs and back muscles were sore for days, but at least I was 
around to appreciate them.

With the 120 VAC tied directly to the station ground it didn't draw 
enough current to trip the breaker.  This was before GFIs were required, 
but with no ground for reference a GFI would not have worked anyway.  
One bac at the panel might have.  Remember, this was in 67 and many 
things were not required and few areas in the country required inspections.

Unlike the elaborate station and tower grounds here  (The 3 towers "over 
there" were not even grounded) and SPG did not exist.  I'd not even 
consider a system like that today, but that was 48 years ago. I'd like 
to think I'm a bit smarter now, or at least a bit better educated.  
We'll let the "smarter" bit remain unanswered.  Lets just say, there was 
a lot we hams didn't know back then.

Unfortunately the current test standards leave much to be desired with 
new hams having to rely on codes, inspectors, and local hams for wisdom, 
so we should try to look over the shoulders of new hams installing new 
equipment and hope we have learned enough to offer advise that will aid 
them in avoiding the dangerous pit falls that we often escaped from 
through sheer dumb luck.  I hope I've learned a lot since the station in 
Breckenridge!

The point is, that the ground was a high enough resistance that it 
didn't pull enough current to trip a breaker So it definitely was well 
over 6 ohms  120VAC/20A=6

73

Roger (K8RI)

>
> 73, Jim K9YC
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-- 

73

Roger (K8RI)


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