[Kenwood] Lightning protection wire antennas WA8OPR

Wed May 14 12:15:34 EDT 2014

On 14 May 2014 at 11:41, Terry Clinard wrote:
> Can someone answer this question:

Maybe...

> Decided to purchase two old style heavy duty knife switches with porcelain
> bases. The gap between the heavy duty copper contacts is a bout 2.5 inches.

OK.

> The live end of the antenna wire is attached to the center knife rocker and one
> of the side psots is connected to the transceiver. Obviously when the knife
> switch is opened it disconnects the antenna. My question is should the opposite
> knife post be attached to an earth ground?

IMHO, yes. For the following reason: it has been pretty much proven by 
experiment (and you can find this info on the web somewhere) that 
GROUNDED and elevated metal objects tend to make lightning AVIOD them.
In fact, a high, well-grounded, metal object, like a BC tower, provides 
protection against lightning strikes for a significant area around it. A sort of 
"safety zone".
I have seen photos of lightning strikes which have, very obviously, flowed 
around a grounded and elevated metal structure. The strike is "bent" in the 
photos.
The safety zone around such a grounded metal object is fairly wide too. As I 
remember it, that zone is as much in radius as the antenna or tower is tall.
The only antenna I presently own is a 55' tall vertical, which is always at DC 
ground for this very reason.
There have been lightning strikes all around my location, but so far, no 
damage has occurred to any piece of equipment I have here.
> This then puts the wire in the air
> directly to ground.

Yes. Is good.
> Now with the antenna going to true ground raises the
> negative potential of the wire in the air.

That is not necessarily true.
Do some research on lightning research. There is plenty of info out there on 
it.
> I am thinking that one does not want
> to do this, because now you have created a high (55 foot) negative conductive
> path for lightning to target. Should the antenna be grounded or simply turned
> off with the 2.5" knife switch air gap?

First of all, a 2.5" air-gap would not be even noticeable to a lightning strike. 
We are talking about several hundred thousands, perhaps millions, of volts at 
10s of thousands of amperes. A 2.5" gap in such conditions is simply 
laughable.
Secondly, as I have tried to make clear above, research proves that lightning 
AVOIDS a properly-grounded, elevated metal object.
I think you would do far better to make absolutely certain you have an 
EFFECTIVE ground system.
Mine consists of several 8 foot ground rods, driven to within a few inches of 
their ends, all tied together with welding cable, PLUS as many radials as I 
could put down, all tied to the rods. And the purpose of the welding cable is 
not to be able to carry significant current, but to reduce the circuit-resistance 
to minimum.
Also, be aware that some designs of antenna couplers automatically assure a 
continuous DC ground.
This is another reason to have an effective ground system.
Ken W7EKB