--- 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
>
>
I don't know where to find it right off, but in one of
the older ARRL handbooks there is a chart where you
measuer the swr of an open or shorted line and see
what you get. Depending on the loss of the coax you
should see so much swr. The higher the swr , the
lower the loss of the line. This is provided there is
not some dammage to the line that would upset that .
If the line has water in it, it should have a higher
loss and a lower swr.
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