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Re: [TowerTalk] Yagi lightning protection

To: Tom Rauch <>,"Chuck Gooden" <>, <>
Subject: Re: [TowerTalk] Yagi lightning protection
From: Jim Lux <>
Date: Wed, 24 Aug 2005 21:29:03 -0700
List-post: <>
At 08:15 PM 8/24/2005, Tom Rauch wrote:

> > Wouldn't the cost of attempting to protect a relay be more
>than the
> > relay cost?
>No. It would be very simple and inexpensive to protect an
>open frame relay that size in a system where the voltage
>across the relay in normal operation is so low.
>I'd do it with wide half-hard thick brass strips bent around
>the case to form a gap or some similar very close spaced
>wide surface air-gaps between the element and boom. There
>isn't any logical reason at all to insulate a large antenna
>element for thousands of volts by omitting a cheap air gap
>when that element might only have five hundred volts
>(element to boom) in normal operation, nor is there any
>reason to not put a bypass gap across relay contacts exposed
>to lightning.
>It might take two hours of total time and cost $20 in
>materials to prevent all the work and expense of replacing
>that relay.

Excellent approach to solving the problem, Tom. I had seen little vacuum 
gaps (like the ones from Victoreen) used for this kind of thing, but I had 
always figured they'd just explode.  However, in this application, the big 
burly gap would work, and the extra parasitic C could just be tuned out.

However, if a manufacturer were to add the 2 hrs and $20 of parts it would 
increase the selling price of the antenna by $100, if not 2 or 3 times 
that, and you'd get countless whines on about how expensive that 
antenna was, and why are they charging all that extra money for a dollars 
worth of copper, etc., and you'd lose some sales.  By and large, the ham 
market doesn't seem to pay for ruggedness like the commercial market 
does.  Personally, I'm willing to pay the cheap prices for the fragile 
gear, and accept the risk, however, you'll not catch me putting it up on 
top of a 100+ ft tower, unless it's real easy to get to and fix.

>My ~200 ft tower has spark gaps at the base and I haven't
>ever lost a component related to feeding that tower despite
>the fact the gaps show evidence of dozens of hard arcs from
>73 Tom


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