Re:
>> “But the current loop/probe has to be
>> looped around either
>> the center conductor.....or the braid, but not both. Same as clamping
>> on a 60 hz circuit,
>> only one conductor passes through the probe. Otherwise the opposing
>> fields will cancel.”
You have just described how to measure the differential current out and back to
the antenna. Two measurements described above givesyou two currents, which if
truly balanced (often unattainable, even with twin lead and hopefully balanced
antenna)
When you run the intact coax thru the sensor, you are reading the longitudinal,
or Common Mode Current, the source of feedline radiation.
Google Owen Duffy, couple of great articles, and Lloyd Butler VK5BR, whose 2009
design reflected only current balance on each leg of feedline; and after course
correction suggested by Duffy revised his device to measure each of
differential current and longitudinal (Common-Mode) currents.
Note Butler’s device works on either coax or twin-lead, as circuit floats in
plastic box.
https://owenduffy.net/module/icm/
https://owenduffy.net/blog/?p=458
http://users.tpg.com.au/ldbutler/Line_Bal_Test_Meter.htm
73,
Ed McCann
AG6CX
Sausalito, CA
Sent from my iPhone
On Jul 2, 2020, at 8:29 AM, Dave Sublette <k4to.dave@gmail.com> wrote:
>>> But the current loop/probe has to be
>>> looped around either
>>> the center conductor.....or the braid, but not both. Same as clamping
>>> on a 60 hz circuit,
>>> only one conductor passes through the probe. Otherwise the opposing
>>> fields will cancel.
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