James, you can tell the same way you can tell if your power supply is
putting out any voltage: measure it.
CMC flows on the outside of the coax, not on the inside.
Use an RF Ammeter with a clip-on sensor.
Most people build their own simple circuit for measuring CMC.
GM3SEK (of RSGB) describes a simple circuit you can build.
If you don't care to build, you can buy a meter starting for about 50 bucks.
I purchased the MFJ-854 for about 100 bucks. It costs more, but is
sensitive enough to measure CMC even when using an analyzer as a signal
source.
The only thing you must be careful of is, the readings vary depending on the
position of the coax within the sensor.
In order to assure I always have apples to apples comparison, I built a
short 1 ft. long RG-213 stub with PLs on each end, wrapped a bit of tape
around it in the middle and clamped my meter over it. It's a snug fit.
That way I can insert the coax stub at any position I wish to measure and
always get an apples to apples comparison.
Of course if you want to see the variances of CMC along your coax (and they
can be huge), then you have to remove the coax stub.
For more info on how CMC varies along the coax, see Steve's (G3TXQ) page on
RF Chokes, and read the bottom of the page.
You find it here: http://www.karinya.net/g3txq/chokes/
73
Rick, DJ0IP
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Richards
Sent: Wednesday, July 10, 2013 6:47 AM
To: rmcgraw@blomand.net; Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Tuner
Golly fellers, I guess I feel pretty foolish now, because, until today, my
OCF dipole was working pretty well, with no evidence of feed line radiation.
How can I tell if there is unwarranted feed line radiation? I see no
evidence of it, and my antenna analyzer says all looks pretty good, and
cannot imagine how I went so far wrong?
---------------- K8JHR -----------------
On 7/10/2013 12:18 AM, Robert Mcgraw wrote:
> All of this as well as others posting says typically the OFC antenna
> is problematic in nature.
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