Re: Using HV COAX without stripping the shield

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Kurt Schraner" <k.schraner@xxxxxxxxxxx>

Hi Gerry,

please see http://www.pupman.com/listarchives/2005/Oct/msg00610.html

BTW: the braid of the coax should be shown grounded. Please view in fixed font.

Cheers,

Kurt


----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Thursday, November 03, 2005 4:40 PM
Subject: Using HV COAX without stripping the shield


> Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
>
> Hi All,
>
> It has been mentioned in the group in the past that there can be a 
> high frequency resonance when using a coax cable such as RG8U to 
> connect the HV from a PIG to the TC where the PIG is remoted from 
> the TC.  This resonance can cause a higher voltage standing wave on 
> the PIG end of the coax.  Dr R has suggested stripping the outer 
> braid of the coax to minimize the transmission line effect,  It 
> seems like to me that doing so changes the characteristic impedance 
> of the cable and doesn't really eliminate the problem.
>
> I was wondering if anyone has experimented with adding a series RC 
> termination to the pig end of the coax to effectively terminate the 
> coax. The C could be a string of C's to get adequate HV capabilities 
> and the R would be 50ohms if the shield wasn't removed or say 300 
> ohms if the shield was removed.  The RC time constant would be set 
> to be higher than the resonant frequency of the TC and yet low 
> enough to effectively terminate the coax for the high frequencies 
> where the coax length would resonant.
>
> Gerry R.