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## Re: [TowerTalk] Pl-259 Flash over voltage

 To: "K8RI on TowerTalk" , Re: [TowerTalk] Pl-259 Flash over voltage Jim Lux Fri, 01 Dec 2006 16:49:18 -0800
 ```At 04:19 PM 12/1/2006, K8RI on TowerTalk wrote: >The talk about breakdown voltage which is basically air across the space >between the inner and outer conductors at the PL-259. Given LMR-400 has >roughly 34 pfd per foot (23.9) or 230 pfd per hundred feet that is not a lot >of capacity. Why would the capacitance for 100 ft not be 100*the C for 1 foot? Something is weird here. But, even 1000 pF or so, when charged to 10kV, can make a fairly impressive spark. Energy = 1/2*c*V^2.. if V in kV and c in uF, then E in joules. 50 mJoule in this case. >The arc is initiated when the breakdown voltage across the gap is reached, >but when the arc is a bright blue and extends out from the end of the >connector by a 1/4 inch or more it has to consist of much more than a >microamp. yes.. the charging current is a microamp. The discharge is probably several hundred amps ( consider it as several kV being fed from a 50 ohm source) > I'd guess the brightness, thickness, and amount the arc extends >out from the tip are determined by the magnetic field induced due to rise >time and current. The diameter (and the brightness) are almost entirely determined by the current. >So I wonder just how much current could be in some of these arcs. I >wouldn't think it'd be much due to the small capacitance, but the size of >the arc, the brightness, the sound volume, and the poke they sometimes give >indicates a substantial charge. Where would that come from? Remember we >are not talking about induced voltages due to nearby lightning strikes. You've got something akin to charging a Leyden jar with a electrostatic apparatus. slow charging, fast dicharging. (actually, the Leyden jar discharges much faster.. very low inductance) >Roger Halstead (K8RI and ARRL 40 year Life Member) >N833R - World's oldest Debonair CD-2 >www.rogerhalstead.com > >_______________________________________________ > > > >_______________________________________________ >TowerTalk mailing list >TowerTalk@contesting.com >http://lists.contesting.com/mailman/listinfo/towertalk _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
 Current Thread [TowerTalk] Pl-259 Flash over voltage, K8RI on TowerTalk Re: [TowerTalk] Pl-259 Flash over voltage, Jim Lux <= Re: [TowerTalk] Pl-259 Flash over voltage, K8RI on TowerTalk Re: [TowerTalk] Pl-259 Flash over voltage, Jim Lux Re: [TowerTalk] Pl-259 Flash over voltage, Pat Barthelow