The inductance of a coil of coax is in series with the rest of the
transmission line, and if that line looks capacitive (by virtue of its
length), the coil of coax DOES NOT WORK to provide isolation. Indeed, it
increases common mode current on the line rather than reducing it.
Effective common mode chokes work as a result of a high value of
RESISTANCE that is inductively coupled from a lossy ferrite core.
Resistance cannot be cancelled, so it always reduces the common mode
current. You can find a thorough discussion of these principles in
k9yc.com/RFI-Ham.pdf and in the ARRL Handbook.
73, Jim K9YC
On 12/12/2017 10:02 AM, Chuck Gooden wrote:
A coil of wire is an inductor with an air core and the principle of of
a inductor will still apply. However an air core inductor will not be
as efficient as an inductor with a core depending on the mu of the
material used.
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