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:

Am Saturday 26 September 2009 14:44:52 schrieb Robert Vassar:

I'll second that. First, a nearby hit is much more likely than a direct one.
And even though there are some standard tests, at a direct blow all bets are
off anyways. So the most likely way to have equipment affected by lightning
is in fact induced voltages/currents from nearby strikes.

The "box method" described by Robert is actually (IMHO) the only approach that
is usable, even though i myself would introduce more than one level of boxes.
Over here (Germany, that is), the most common approach has three or four
levels of boxes with their own protection levels. The outermost box will thus
handle the most severe stuff and limit exposure to overvoltage for the inner
levels. So, the inner protection devices don't have to handle a real hit but
only "minor" overvoltages, which occur much more often that the really scary
ones. Chances are, that a strike won't reach the innermost level of
protection, and due to the spread of protection over a couple devices, one
failing won't kill your equipment.

HTH,
Florian

Others have made good comments about zones.  HP and Symmeritcom made
lightning protectors for GPS, they use "N" connections - and I have
bought a couple on flea-bay for reasonable prices.

I work repairing two way radio systems, we use Polyphasor protectors and
they seem to do a good job.  But if you take a direct strike, everything
can burn up.

The biggest problem we have here is the soil is rocky, so we have to use
multiple ground rods to dissipate strikes.  We come off the tower legs
and usually use two ground rods, one near the base and another 6-8 feet
away for each leg of the tower.  We also put ground rods around the
shelter at each corner and this ground is tied into the electrical
ground in the shelter.  Then this ground is attached to the RF and
telephone line lightning protectors and all radio equipment.  When we
have had to dig up and replace the telephone lines we also bury a #4
ground wire running beside the telephone lines and we attach it to the
ground system.

Brian - KD4FM

Jim Palfreyman wrote: