There's definitely a power rating, and at 50 ohms you
can figure out the RMS voltage, then the peak-to-peak
voltage, but that won't be the breakdown voltage that
the insulation is capable of. Those specs are
available on the Andrew web page under Heliax.
The only thing that I can think of that might be "a
bad thing" would be if, during the process of megging
it, you caused an arc to form which left a carbon
trail in the insulation. That would kinda render the
cable useless.
As you said, the TDR and wattmeter/dummy is about all
you can easily do. A spectrum analyzer and a return
loss bridge might give you the same indication as the
TDR if the coax is good.
Bob M.
======
--- dallasreact112 <[EMAIL PROTECTED]> wrote:
> I have access to a spare run of about 150' 1-1/2"
> heliax at a repeater
> site. It goes from the "Radio Room" to the roof.
> There is no antenna
> connected to it. I would like to verify if it still
> any good.
> Obviously, hooking it up to a TDR would be a
> preferred method of
> verification. Next best method probably would be
> hooking it to a
> transmitter with a Bird thruline at the transmitter
> and a Bird
> termaline at the end on the roof. I could then
> verify SWR and verify
> actual transmit loss. Lacking that, I wonder if a
> megger, which I do
> have, might be of use? If I were to suspect if the
> heliax is bad due
> to moisture incursion, one might be able to see a
> low resistance path
> between the center conductor and outer shielding.
> Has anyone tried this?
> Is there a spec, or reasonable approximation for
> insulation resistance
> center to shield per 100 ft or the like?
>
> 73 and Thanks
>
> Bernie Parker
>
> K5BP
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