[time-nuts] Lightning arrestors for GPSDO antenna

Bill Hawkins bill at iaxs.net
Sat Oct 18 17:05:25 EDT 2014


FWIW, when grounding the metal mast of a boat, three inch wide copper
strap is used because it is a better RF conductor. The strap is
available
in marine supply stores.

You really don't want lightning punching one or more holes in your boat,
so whatever hits the mast (usually the full stroke, not a side shoot)
gets directed directly to the keel.

IIRC, gas discharge tubes take some time to ignite, so something faster
is required to take the initial current.

Bill Hawkins


-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Dave M
Sent: Saturday, October 18, 2014 12:48 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Lightning arrestors for GPSDO antenna

Chris Albertson wrote:
> On Thu, Oct 16, 2014 at 7:51 PM, Dave M <dgminala at mediacombb.net>
> wrote:
>
>> Thanks, Chris.
>> I've done a bit or research on the subject, and think I have a 
>> reasonable grip on the necessary steps.  I have an 8' ground rod 
>> driven into the ground directly under the spot where my antennas 
>> mount.  #6 solid copper from the rod to a heavy aluminum plate, where

>> the arrestors will be mounted.  A #6 solid copper wire from the plate

>> to the antenna mounting structure.
>
>
> About the only thing you left out is the interconnection between this 
> new ground rod and the existing house ground.
>
> Sounds like you must live in Florida.  The best source of information 
> is the lightening lab at University of FL.
>
> I've never read a good research backed paper on plastic v. metal 
> conduit. I bet it does matter.  I use iron pipe outdoors then after it

> gets indoors switch to plastic.  Practical reasons.  The flexible 
> plastic conduit is just easier to use

Actually, I lived in Florida for about 40 years, retiring to north
Alabama about 5 years ago.  about 6 of those years were spent working at
a Motorola 2-way radio shop.  So, yes, I'm pretty familiar with the
damages that lightning can cause, and some of the precautions that help
minimize susceptability and damage.

As I posted earlier, I've seen writings promoting metallic and
non-metallic conduit for the antenna coax.  I can see reasons for
placing the coax in metallic conduit.  But, one thing that I've read
that is consistent, is NOT to run the earth ground wire in metallic
conduit.  That's to keep the current to ground in a solid, unbroken
path, which the fittings used to join conduit can't provide.  OK to run
it in non-metallic conduit to keep it out of the weather.  Since my coax
run is only about 20 ft, I'm thinking that I should be OK with the coax
in 1/2" galvanized steel conduit. I agree that the metallic conduit
should stay outside, and not be connected to the equipment ground
inside.  I'll run a separate ground wire from the equipment rack to the
ground rod outside.

Cheers,
Dave M


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