Re: Using HV COAX without stripping the shield

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "MIKE HARDY" <MHARDY@xxxxxxxxxx>

Wouldn't putting the HV cable in grounded aluminum conduit be the same as
using a grounded braided shield?
----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Tuesday, November 08, 2005 10:37 PM
Subject: Re: Using HV COAX without stripping the shield


> Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>
>
>
>
> Usually a piece of PVC tubing will not most everything.  The PVC has
> a rather high instataneous breakdown level and the sparks tend to
> avoid it. It's usually available in 20 ft. lengths from large
> plumbing supply houses. One could also use aluminum conduit from an
> electrical supply house and ground it.  Either method seems to work
> well.  We lerned this the hard way after he Big Bruiser damage our DC
> motor control diodes in the remote control console at the Thon.
>
> Dr. Resonance
>
>
> >I have one nagging concern about using unshielded hv cables on a big TC.
The
> >possibility of ground strikes hitting these lines, and for that matter
the
> >SG control lines. Especially without  breakout point. How about throwing
> >grounded chickenwire or screen over the cables near the coil? Any problem
> >there?
> >----- Original Message -----
> >From: "Tesla list" <tesla@xxxxxxxxxx>
> >To: <tesla@xxxxxxxxxx>
> >Sent: Friday, November 04, 2005 12:53 PM
> >Subject: Re: Using HV COAX without stripping the shield
> >
> >
> > > 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.
> > > >
> > > >
> > >
> > >
> >
> >
>