[TowerTalk] Lightning Protection Question

[jimlux]

Roy K. Breon wrote:
>  I remember seeing several articles in the 50's that used automobile spark
> plugs as lightning arresters.  That was when you could get a plug w/o a
> built in resistor.  Can you do that today?  Comments?
> 
You can get non-resistor plugs. I've used them as vacuum HV feedthroughs.

As a spark gap, they'd work ok, but a couple pieces of sheet metal might 
be easier and more compact.  Things to think about with spark plugs:
1) the thread is odd, so getting a suitable nut to fit is hard.. the 
plug is cheap, the nut is not.  If you were doing a bunch of them, you 
could get a spark plug tap and thread the chassis.  Again, the tap isn't 
particularly cheap ($10 ish, plus you need a tap wrench, and you need to 
be careful so that the tap goes in straight).. and, sparkplugs are 
designed to seat into a conical seat.

2) They're sort of big and bulky, compared to a couple of pieces of AWG 
10 solid wire.  They ARE rugged.

3) You want a plug brand that has the removable connection thing on the 
top that leaves a threaded rod sticking out.  A lot easier to put a ring 
lug on than trying to solder/braze/connect to the little knobby thing.

4) you want a cheap conventional plug.. no fancy platinum wires, etc. 
You're going to be setting the gap pretty close (say, 0.030 to 0.040 
inch or so)

SO it's mostly a matter of fabrication tradeoffs.