Tower Talkians:
Three years ago, I purchased almost 100 feet of a LMR400 "equivalent" from a
well-known, reputable vendor at the Dayton Hamfest. It appeared to be a
well-made, high quality cable.
Before installation (which was to be for a 122 Mhz airport unicom station), I
decided to test the cable at 1.8, 7, 10, and 14 Mhz for performance against the
published specifications. I do this by feeding and measuring 100 watts into the
cable and then measuring the actual power output at the end of the cable into a
52 ohm dummy load. This methodogy has proved (for me) to be highly reliable. I
have measured all of my feedlines up through 52 Mhz using this method with
consistent results.
I was quite surprised to find that my practical test results showed that the
loss in the cable was higher than the published specifications for LMR 400.
While it was only one sample of the LMR 400 "knock-off, it had relevance for my
purposes.
I believe that when it comes to coax, you get what you pay for. I have some
runs of Belden 8214 foam feeding my antennas (including a 6 meter beam), that
are 26 years old and still performing reasonably close to specification.
Because of my experience with the LMR 400 clone, and other private branded, or
lesser known brands of coax, I choose my coax carefully depending upon the
length of the run involved and the frequency of operation.
73, Dennis W0JX/8
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