[TowerTalk] Re: Ground Rods & Ohms

[John Allen]

I think that a digital ohm meter would work.

One ham I know runs a wire (#10 or larger?) a few hundred feet
to a brook where he gets a good ground.  I works very well for him.

I have 3 8 foot rods at the base of the tower into fairly poor
and dry soil and no salt or conductivity enhancer.  I was hit by 
lightning - a direct hit on the tower -  the following resulted:

1. antennas were disconnected, but the 6M coax was about 6 inchs away
from the side of a rack cabinet.

2. All of the bolts holding the Rohn 45 sections together were 
loosened by several turns!!!  EXCEPT the sections that had aluminum 
conductive grease at the junction  (Hint: do the inside of the bottom 
of each section instead of the outside of the top of each section and 
you will have much less grease on your clothes when done.)  The clamp 
screws on the ground rods were also very loose.

3. The 6M coax arc'd over the 6 inch space to the (grounded) rack.
(How do I know? - there is a 1/2 inch dia molten spot on the N 
connector and a matching burn spot on the steel rack.

4. The power supplies in the rack and the 6 and 2 M (tube) amps were 
fine.  But the 6M and 2M ICOM 551/251 xcvrs are HISTORY 
(unrepairable, totalled).

5. The current went from the rack to the above rigs and also into
the shack's power/neutral line.

6. Everything connected to the phone line that wasn't a phone (ie
answering machine, modem) was fried.

7. Random other appliances (only a few) were fried.  Including a 
Cuisinart food proccessor and a subwoofer and the ac side bypass caps 
of my audio power amp.

So don't laugh when you see someone worry about the ground resistance
of tower grounding and don't laugh when you see someone move all of 
the coaxes 6 or more feet away from the shack entrance.

73, John K1AE, ex K1FWF

> A short time ago someone indicated they had measured the resistance
> on their ground rods.  How does one do this?  Can it be done with
> something as simple as a digital volt meter?  What two points do
> you measure between?  I don't live in a particularly sandy area but
> have no idea if my ground rods (6) will actually help if lightning
> should visit.
> 
> Thanks,
> 73  Wayne  AJ5M  ehayes@vnet.ibm.com
> 
> 
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