This link shows the base of a typical AM broadcast tower, with two hard steel
balls used as lightning protection. At kilowatt power levels its not unusual
to use a credit card to set the gap.
http://www.thebdr.net/articles/steel/twrs/LimitingStatic.pdf
73
Frank
W3LPL
---- Original message ----
>Date: Fri, 27 Jul 2012 16:29:15 -0400
>From: "Tom W8JI" <w8ji@w8ji.com>
>Subject: Re: Topband: Spark gaps
>To: "Mike Waters" <mikewate@gmail.com>, "topband" <topband@contesting.com>
>
>> Man, I don't know, Dave. How long have they been selling those carbon
>> balls
>> for that purpose?
>
>I've never seen a carbon ball in a lightning gap application. I'd have to
>see a few after being in action a long time before trusting them.
>
>Broadcast stations use hard metallic balls, as do electrical substations and
>other applications where the peak voltage is near gap voltage. Polished
>round gaps have more consistent breakdown.
>
>If there is a great deal of headroom between operating and breakover
>threshold, a pointed gap works OK.
>
>_______________________________________________
>UR RST IS ... ... ..9 QSB QSB - hw? BK
_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK
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