[TowerTalk] Lightning GROUND switch wanted

[Tom Rauch]

> costs ~$2 each in small quantities.  It would seem that such a relay can't
> offer the sort of protection from lightning that he describes, if only
> because the physical spacing between contacts is very small.

It depends on the contact arrangement inside the relay. The gap 
isn't as important as the pass-through isolation and contact layout. 
The same things that reduce pass-through on VHF on a de-
energized relay reduce lightning problems.

Putting a grounded armature in the way and isolating the center 
conductor at either side of that grounded armature is the key, 
because any arc has to go to ground. Simply opening a contact 
doesn't work well, unless the voltage from a hit is very low.

> So, the next question is, what relay does Ameritron use in the RCS-8? 
> Many of us might be interested in homebrewing a grounding panel with them,
> if the cost isn't too high.  Tom?

It's a custom relay, for PC mount only. You'd have to look for a 
form X double position contact, one that pulls a shorting bar across 
the contacts and keeps the input and output contacts physically 
well separated with the grounded armature as a barrier.

Keep in mind only grounding or unscrewing cures the common 
mode issue. All lightning arrestors can do, or isolation devices can 
do, is limit stuff inside the cable or on the conductor attached to 
the relay.
73, Tom W8JI
w8ji@contesting.com

--
FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com