Roy's Measurements

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W7EL's Antenna current measurements:


Inductor measurement setup

This is the overall measurement setup described in the newsgroup
on and about November 9, 2003, showing both traces on the oscilloscope. Signal input is
from an HP 8640B signal generator.

Closeup of measurement setup

This is a closeup of the inductor and current probes. The upper pipe is the vertical antenna.
The one to its left is the mounting, which extends about four feet above ground. The two are
spaced 1/4" apart. The yellow toroid is the inductor being measured. The smaller black cores
are the current probes. One core of each probe is a transformer, with the wire carrying the
current to be measured passed through the core's hole. The second core is a common mode
choke or "current balun", which serves two functions. One is to insure that no significant current
flows on the outside of the coax cables connecting the probes to the oscilloscope. The second
is to isolate the probes and reduce any possible capacitive coupling that might disturb the
measurement. The probe outputs are terminated with 50 ohms at the scope.