Re: Using HV COAX without stripping the shield

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Mike" <induction@xxxxxxxxxxx>

Hi Jim,
              Yes I am aware of the Plastic Vs foam issue, Velocity 
factors being ~ .66 plastic and  ~.88 foam. Have made many phase 
delay lines for directional broadcast towers, phase monitor pickup 
loop lines plus directional arrays for ham usage over the decades.
What I could not remember offhand was the Pf per foot for peak 
current storage. Also aware of the Z, OD of  inner to ID of outer. 
Like yourself, I have an interest in seeing the remote cable 
interface behave itself.
Best to you,
Mike


----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Friday, November 04, 2005 5:40 PM
Subject: Re: Using HV COAX without stripping the shield


> Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>
>
> At 10:50 AM 11/4/2005, Tesla list wrote:
> > Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
> >
> > Hi Mike,
> >
> > I'm not necessarily taking issue with Dr R.  I'm suggesting an 
> > alternative way to fix the problem.  Getting rid of the coax 
> > shielding doesn't get rid of the transmission line, but it 
> > certainly does change it and this may be enough to "fix the problem".
> >
> > BTW, RG8 is 50 ohm cable and the dialectric is PE not foam.  75 ohm 
> > cable typically uses foam to get the higher Zo.
>
> 50 and 75 is independent of foam (in that, you can get solid or foam 
> dielectric for either).  The foam is used for lighter weight and 
> lower loss at high frequencies (e.g. for Cable TV at hundreds of 
> MHz, dielectric loss is important).  Solid has a higher breakdown 
> voltage. Foam has a higher propagation velocity (because epsilon is lower).
>
> Impedance (Z0) is a function of the ratio of inner and outer 
> conductor diameters (and dielectric constant).