Re: coax cable with AC pole xmfrs

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Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Dr R.

> Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>
>
> A transmission line is essentially a capacitor, ie, plate, 
> dielectric, and another plate.  Removing the shield of x-ray cable 
> leaves the PE/PP and no second plate, so the normal xmission line 
> effect is now missing.

Removing the shield reduces the capacitance greatly, but you do still 
have a xmission line, just not a coaxial one.  There is still 
distributed capacitance on the unshielded cable to earth and other 
objects and there is still a distributed inductance in the 
wire.  Removing the shield has changed the impedance (and its 
controllability) and the velocity constant.

I believe that removing the shield stopped your creepy crawlies, but 
do you know why???  Is it because the resonance of the cable 
changed??? or because the capacitance changed???  10 foot of RG8U is 
about 290pf and this isn't very much in the scheme of things.  You 
may be able to emperically test theories by adding back the 
capacitance descretely and see if flashover comes back...  or 
terminate the coax and see if this also fixes the problem. It would 
be nice to know exactly what the mechanism is to evaluate safety 
margins and other solutions.

Gerry R