[time-nuts] GPS antenna and lightning

Robert Vassar rvassar at rob-vassar.com
Sat Sep 26 12:44:52 UTC 2009


Greetings,


We get a fair bit of lightning here in Texas.  I'm a transplant from  
nearly lightning free California, so I had to go thru an expensive  
period of education.  A couple quick thoughts:

Nothing will save you from a direct strike.  At least nothing you can  
likely afford.  You're more likely to get clobbered by a surge from  
the grid, or induced voltage from a nearby strike.

Use the "box method".  Draw a diagram of your equipment, then draw a  
large box around it.  Any wire that enters or leaves the box requires  
some kind of protection device.  In the case of a GPS antenna, likely  
a relatively expensive gas discharge tube bonded to a properly  
installed ground rod by a short length of heavy copper braid.


That said, I still can't bring myself to leave my HF radio gear  
connected to an antenna all the time.  I unplug mine when not in use  
and place the lead in a stoneware jar on the floor of my garage.


Rob
KC6OOM/5


On Sep 26, 2009, at 4:37 AM, Jim Palfreyman wrote:

> Hi All,
>
> I live in Hobart, Tasmania which has low level of thunderstorms -
> average 2 thunder-days a year. However recently we've had a few and
> I've begun to think about my GPS antenna on the roof on top of my TV
> antenna.
>
> A bolt on that could take out not only my plasma tv but potentially an
> awful lot of time equipment that is precious to me.
>
> For those of you in lightning prone areas, what precautions have  
> you taken?
>
> Regards,
>
> Jim
>
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