[time-nuts] Best location for a GPS antenna...?

[Chris Albertson]

On Thu, Apr 12, 2012 at 12:02 PM, David McGaw <n1hac at alum.dartmouth.org>wrote:

> Best would be to have a lightning rod in the vicinity of and above the
> antenna.  A sharp-pointed rod does not attract lightning, it REPELS it and
> has a cone of protection under it.  While the effect is not understood, it
> apparently discharges the surrounding air through corona discharge - the
> sharper the better.
>
>
Yes.  That is why.   Air normally is a decent insulator.  But if it gets
ionized (charged) then it can conduct.  The way lightening works is the air
gets more and more conductive until finally there is a weak path then
current starts  to flow, the current further ionizes the air along the path
allowing even more current to flow which ionized more air and you get a
run-away reaction what a huge current then flows which heats and rarefies
the air which in turn breaks the conductive path.

You can protect yourself by NOT being near that first weak ionized path.
 One way is to firmly ground the air around you so that it remains
un-charged.    But how to do that is kind of a black art.

The other way to protect yourself  build a "voltage divider"  just like
you'd make with a pair of resisters.  Current will flow in proportion to
the resistance.  So you wire your roof via a "milliohm resister" to ground
and hope the current will divide and 99.99% of it goes through the large
ground strap (aka milliohm resister)

But as it turns out the ground strap works as both a voltage divider and a
means to ground the air to prevent it from being ionized.

I hope this explains why a lightening rod can both repel lightening and
protect you from a strike.




Chris Albertson
Redondo Beach, California