Chuck:
I don't want to start a grounding uproar but it sounds like you didn't have
a good single-point ground system, like what Jim Brown describes in his
papers. You may have good solid grounding but somewhere there is (or was)
apparently a path between your station ground system and another ground
system (your house electrical ground) even though you probably didn't intend
to have two separate ground systems. That is really the only explanation
for lightning going to ground via a clock and down through your amp to the
amp's ground.
TV and radio station transmitter/antenna sites routinely get hit by
lightning and they rarely go off the air because of a strike. I worked as a
control room engineer during summers at Channel 12 in Shreveport (a long,
long time ago when we used vacuum tubes) and I don't recall the station ever
going off the air because of a lightning hit.
I no longer have any beams on tall towers but at my previous station I did
have stacked beams on a 70' tower. I also had a 2M vertical sticking up at
the very top, which I didn't use very often because I never really enjoyed
2M. I remember walking down my driveway to get the morning paper and
noticing little pieces of fiberglass and metal on the concrete. It took a
few episodes of this to get me to look up and then I realized that lightning
was hitting my 2M antenna and slowly whittling it down. It was only 2' or
3' tall when I noticed this. Nothing ever happened inside my house or
shack, despite all these hits over a period of 20+ years.
For grounding the antenna coax cables I used ICE arrestors bolted to a heavy
copper bar outside my shack window. The bar was securely fastened to four
8' copper plated ground rods. Everything in the shack was grounded to one
single piece of copper strap that ran through the wall to the bar outside. I
also tied this ground to the electrical service ground which, luckily,
wasn't too far away.
At my current QTH I have the same old ICE arrestors, still doing fine. When
we built our current house about 15-years ago I drove two copper-covered
ground rods into the trench where one of the slab beams was about to be
poured, and directly behind the soon-to-be wall of my operating position.
Four ICE arrestors are mounted to 4" copper strap clamped to the tops of the
rods. My station ground strap (about 4' long) also goes to this spot.
My thought was, rightly or wrongly, that maybe pouring the slab around the
two ground rods would create some form of Ufer ground. I don't know whether
this is true or not.
The antenna cables are RG-8 BuryFlex run from shack to 4 spots out in the
backyard. The cable goes through conduit in the slab and then underground
to the 4 ICE arrestor points. The arrestors are each mounted on a piece of
4" copper strap tightly clamped to the tops of 8' ground rods. I covered
the ground points with slightly decorative clay pottery pots.
I also ran another piece of 4" copper strap from the point behind my
operating desk through the side wall of my shack and out to the same point
where the house electrical and telephone service is grounded. This is about
15' of copper strap.
All I can say is that we get some pretty big thunderstorms at times here in
NW Louisiana with regular hits in various Pine trees in the area and I have
yet to find or experience any damage anywhere. I do not ever disconnect
anything, or switch anything to ground, at any time.
I had the advantage of being able to do all this as we were building the
house. Moving into a house and dealing with whatever you have is another
story and I can see that a lot of hams will encounter some frustrating
problems. Nevertheless, the single-point theory is good advice from Jim.
Unintentionally having separate ground systems is not good and contributes
to a lot of problems.
-------------------
Wes Attaway (N5WA)
(318) 393-3289 - Shreveport, LA
Computer/Cellphone Forensics
AttawayForensics.com
-------------------
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Chuck
Dietz
Sent: Thursday, September 05, 2019 8:37 AM
To: john@kk9a.com
Cc: Towertalk Reflector
Subject: Re: [TowerTalk] Grounding
I had everything disconnected but the ground and a clock on top of an amp.
Lightning surge came through the power lines, through the clock and in to
the amp on its way to ground.
Now I disconnect the ground.
Chuck W5PR
On Thu, Sep 5, 2019 at 8:01 AM <john@kk9a.com> wrote:
> What ground? Do you use a seperate ground going from your radio
> chassis to a ground rod? I have my equipment bonded together but no RF
> ground and no RFI issues.
>
> John KK9A/4
>
>
> K9MA wrote:
>
>
> My theory has always been that, with the station equipment well bonded
> together, it is safe to leave the ground connected, as long as
> EVERYTHING else is disconnected. That leaves no path for current to flow
> through anything. I can disconnect the transmitting antennas with one
> coax, all the control cables and rx antennas with another big connector,
> and power with one 120 and one 240 V plug. That just leaves the ethernet
> cable, which I try not to forget.
>
> In any case, my primary goal is to prevent a fire, and disconnecting the
> ground from the equipment probably wouldn't help there. I hope I never
> have to test that theory.
>
> 73,
>
> Scott K9MA
>
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