[ICOM] Grounding

[Ed Senior]

Hi Bill -

I do not claim to be a lightning expert; but I am an EE, and have
been reading some on the topic.  (The XYL makes me.)

First off, there isn't just one type of "ground" connection.
There are at least three, each with different considerations:
1.  AC safety ground--code stuff, the third wire, etc.
     (This should protect you if your gear has an internal fault.)
2.  RF ground.  (This would include keeping your gear at the
     same RF potential, giving your 1/4-wave vertical a ground
     to work against, and similar topics.)
3.  Lightning ground.  (The goal here is to contain a lightning
     strike to non-destructive paths, on its way from where it
     strikes to where it wants to go--usually ground.)

Re 1.  We can dismiss AC safety as being already satisfied,
unless you've been doing your own non-code wiring.  Big wires
are not needed for this purpose.

Re 2.  RF ground really has nothing to do with what your power
company is talking about.  If you want or need an RF ground,
long, meandering, #10 wires definitely won't give it to you,
as you probably already know.  The good news is that there's
a good chance you don't NEED an RF ground.  I have none in
my second-floor shack, and I don't miss it.

Re 3.  Lightning.  This is the ugly one.  One thing that many
agree on is that lightning will ALWAYS do what it wants to
do--and that often is not what you or the power company want
it to do.  This topic is far too big to discuss thoroughly in a
brief NG post; but I'll make a few comments.

The effect of a lightning strike on a system with (only) a lightly
built, star-type safety ground depends very strongly on WHERE
the lightning strikes.  (Duh!)  If it decides to strike right on your
ground rod, you should be in good shape with little star grounds.
They should nicely float everything up a few thousand volts
during the duration of the strike, with little or no harm done.

But people are usually not lucky enough to take a strike directly
on their ground rod.  All bets would be off if its point of entry was,
say, your phone lines.  It would probably start looking for ground,
and it would likely find one of those skinny ground wires.  And
after vaporizing that one, it might go looking for another one.
The results would likely be very messy--as I believe you recently
experienced.  It is likely that the device the power company is
offering you could provide some protection against lightning strikes
on the power lines, OUTSIDE your house.

If you DON'T have to operate during electrical storms, I believe
the best (and cheapest) approach is to disconnect your antennas
as thoroughly as possible from the house.  And it wouldn't hurt
to try to offering the lightning some very stout paths to ground
OUTSIDE--e.g., a very well grounded tower.

If you DO need to operate during electrical storms, I would call
in the professionals (e.g., Polyphaser).  Be prepared to spend
some money in this case.

Good luck and 73,

Ed, W6LOL


----- Original Message ----- 
From: "William Diamond" <wjdiamond at sbcglobal.net>
To: "Icom at Mailman. Qth. Net" <icom at mailman.qth.net>
Sent: Monday, May 17, 2004 11:26 PM
Subject: [ICOM] Grounding


> Hi folks,
>
> I spent a few hours today with an engineer from the power company as I had
a
> whole house surge device put on my main electrical service.
>
> He said that my present grounding setup is a problem, i.e.., separate
ground
> rods for the tower as well as the radio room.  He said that I needed
"single
> point" grounding system with the tower and radio room tied into the main
> power company ground so there will not be a difference of potential.
>
> He said that a small wire such as #10 will be fine.
>
> Has anyone else heard of this?
>
>
>       William J. Diamond
>        Rogers, Arkansas
>
>     Ham Radio Operator WR0T
>
>    Please Visit My Radio Site
>         wjdiamond.com
>
>
>
>
>