[TowerTalk] Coax Resiliency

[Jim Lux]

> This information is taken from the instruction manual for the Autek VA1
> antenna analyst.

I believe the original poster had a bunch of short chunks, and might not
have a whole 1/4 wavelength.  Same thing works, though.. measure the Z
looking into a mismatch, just you have to do more math to get the loss.

  I use this method of measurement to assess
> deterioration of my transmission lines.  I also measure DC insulation
> resistance and DC conductivity of the conductors.  I'm reluctant to use
> a Megger.  Exceeding the breakdown voltage of a line can permanently
> damage it, depending upon the kind of insulation that breaks down.

One would  want to check the output voltage of the megger.  If it's <1000V,
then the coax shouldn't be breaking down. The voltage rating on coax is RMS
AC volts, and fairly conservative (perhaps they take into account some
mismatch?). Solid dielectric RG-8/RG-213 is good to 20 kV DC without
breakdown (it's actually probably higher than that, but 20 kV is the highest
I've run through it on a regular basis, in air).

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