[Towertalk] Lightning Protection - Conclusion (for me, anyway)

[Tom Rauch]

> bought advising this connection.  But as I described, I already have
> the three coax shields grounded just before they hit the suppressors
> out at the tower. (I'd rather keep the lightning in my back yard away
> from the house than conduct it closer to the shack before it's shunted
> by the suppressors.)

The best place for the suppressor, if you feel them necessary, is at 
the house end of things....not at the tower. Keep in mind what the 
suppressor does, it simply ties the center to the shield when voltage 
reaches nearly 1000 volts.

Placing the suppressors at the tower leaves the possibility of 
lightning ingress into the center conductor from any sort of poor 
shield connection in the system, and damage in the house. 

At the tower bottom, you need good shield grounding. You should also 
bury the cables for some distance and keep them at ground level up to 
the house, where the cable ground should be common to the service 
entrance ground for your house with a very short excellent conductor. 
If you can't do that, then everything in your room should be grounded 
to the feedlines at one point, and then ALL cables (telco, power, 
control, and RF) should leave that point to your equipment.

If you do that you can have your center-to-shield lightning 
suppression in the house, where it belongs. Then if you have ANY poor 
shield connection outside the suppressor will limit voltages to a 
thousand volts or so from the shield to center conductor. Of course 
the BEST practice by far is to disconnect the coaxial cables and 
power line connections TOTALLY by pulling the plugs and ALL 
connections to the outside world.

Keep this in mind....**any lightning suppression device that will let 
a kilowatt or two out will let much more than that back in to the 
station**. Even a few volts can be devastating to the receiver.

The very best thing, short of unscrewing the cables at the bulkhead 
entrance point and tossing them in the yard and unplugging everything 
in your station from telephone and power lines would be to use a 
switch that opens the cables to the radios and grounds the center 
conductors on the antenna side of things.

But again, the key to everything is wiring layout, good connections 
and grounding at some point BEFORE the building is entered, and 
avoiding loops through gear. That's actually about all I do here, and 
my towers can take direct hits without any damage to any gear.73, Tom 
W8JI
W8JI@contesting.com