Re: Using HV COAX without stripping the shield

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

Hi Gerry,

On 3 Nov 2005, at 8:40, Tesla list wrote:

> 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 agree, and have noted problems I encountered in the past with long
leads of any sort.

Malcolm

> 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.
>
>
>