[time-nuts] Lightning arrestors for GPSDO antenna

Dave M dgminala at mediacombb.net
Sat Oct 18 13:47:55 EDT 2014

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.

Dave M

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