That is of course great advice, but in my case almost all of my coax is
either on the tower or buried underground. Climbing up and down the
tower several times taking measurements along the line (the process is
useless if you only do it in one spot since as you say it could be a
current minimum) has limited appeal for me when instead I could maybe
just get a reasonable indication of the impedance of a CMC to have some
confidence that it would work when I install it.
Dave AB7E
On 1/25/2026 10:31 AM, jim.thom jim.thom@telus.net wrote:
## why don't you folks just use a clamp on RF ammeter, and actually
measure the CM current, at several different places along the coax cable
?? The CM current will vary along the length of the coax due to swr on
the outside braid of the coax, even though the ant swr may well be 1:1.
## Mark the coax with tape, where u take the readings from. Then if you
swap to a different CM choke at the feedpoint, or a 2nd, 3rd CM choke
downstream, or 2 x chokes in series, you can compare CM current results
asap.
## The whole idea is to minimize CM current. If you don't actually
measure it, you really don't know what you are dealing with.
## and when taking measurements use the same PO as before. IE: 1 kw CXR.
Jim VE7RF
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