[TowerTalk] Pl-259 Flash over voltage

[K8RI on TowerTalk]

> 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.

Not at all. It's called short hand math. My professors had the same problem 
understanding it in college as you are seeing  I drop the zero and you, or 
the reader is supposed to automatically put it back in. <:-)) I really do 
have a math minor.

>
> 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.

I've been about 3 feet from a 50,000 Joul MOV when it blew. Now there's some 
energy.

Thanks,


Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com