On Fri,8/5/2016 10:20 AM, Rob Atkinson wrote:
You can construct one
and use a dual trace oscilloscope to adjust the network taps so the
sides are 180 degrees out of phase if this bothers you.
But phase is an important part of "equal and opposite." The fields
around the conductors cancel ONLY if they are equalin magnitudeand
opposite in phase. Danny is exactly right -- a measurement that ignores
phase or gets it wrong is a bad measurement.
I agree with Roy's papers on voltage and current "baluns." What we often
call a "current balun" is fundamentally a common mode choke. It does NOT
attempt to force balance -- it works by adding a high resistive
impedance in series with the common mode circuit, which in turn reduces
common mode current. When placed at/near the feedpoint of an antenna, it
essentially removes the feedline from the equivalent circuit of the
antenna. That is, the feedline is no longer PART OF the antenna, but
only provides power to it.
And, of course, even this is an oversimplification -- if the feedline
does not run exactly parallel to the antenna it shows up in the antenna
circuit as a conductor grounded at the bottom end and open circuit at
the top end, and acts as a parasitic element, causing imbalance in the
antenna circuit.
73, Jim K9YC
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