Hi,
Frank's method is fast, and fingers coax as long as the antenna & stuff at
the other end does not change. Quickest way to determine that nothing has
changed. (It is *possible* that the coax could go bad one way and the
antenna bad in an opposite and equal way, and therefore show no trouble, but
what are those odds?)
If you have a dummy load and a Bird, then the brute force method is to put
dummy load at the far end of the coax in question. Send 50 or so watts up
the coax at the frequency(s) you use. Measure the power with the Bird at
both ends of the coax. Write down the measurements and their ratio. Use any
other power measuring device at the transmitter to keep the power constant
for any given measurement pair.
If the coax starts going bad, the ratio will start to rise. The ratio
represents the loss in the cable and can be converted to db.
Another test I use is 50 ohm resistive termination at far end and watch the
indicated swr as I sweep from 1.8 to 30 (for HF) using the MFJ impedance
box. It should be very nearly smooth. If it has peaks and valleys, and the
termination or connectors aren't hosed, the coax is bad.
Once I had an 8 inch piece of RG8 with UHF connectors on it that worked OK
on 3.5, but was a 20 db attenuator on 440. I wish I'd kept it. (For show and
tell, not to use.)
Never know what you're gonna find...
73,
Guy.
-----Original Message-----
>I just installed several new runs of coax and hardline, and would
>like to know what methods you use to check on your feedline's
>condition.
>
>W3LPL talked about this at Dayton a few years ago.
>>>From my notes, it went something like this:
>
...snip...
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