Briefly, I wanted to phase air transformer baluns for an upcomming antenna
project. The baluns are unmarked and according to the manufacturer are
not assembled with any set configuration.
If you have a lab grade ohm meter, it is possible to measure the DC resistance
of the coil to the center terminal. It is expected to be LOWER than the shield
side. Measure from both outputs of the balun. Lower is center.
If you have a noise bridge, set up the balun and your receiver to measure
inductive reactance - XL. You will have to tune the receiver to a proper
frequency. If you get XC, go lower. Short the output of the balun to the
shield of the balun. The center terminal is connected to the side with the
LOWER XL.
Verification: I took the 4 baluns to work after I had marked them with
the configuration that I presumed correct. Three were identical and one
was opposite. They were X Rayed to reveal the coil windings and solder
connections. I traced the windings on the film, without looking at the
markings I had placed on the balun, and was correct in my measurements.
73, Dave KN2M
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