To All from PA0SE
Andy, G4JNT wrote:
But these harmonic currents will upset your readings somewhat - where on a
scope trace is the RMS value of
a) the total waveform and
b) the fundamental ?
The harmonic currents will obviously be out of phase with the harmonic
voltage, and cannot exit the top of the coil so if they are indeed
entering
the coil base they must be completing their loop in the fields from the
coil
itself - the quadrature, non dissipative, H or E fields. Very little
radiation field will be generated from such a small radiating element,
even
at harmonic frequencies.
The current into the coil, displayed as the voltage over the resistor in
series with the coil, looked like a pure sinewave. So the harmonics were
only present in the transmitter output VOLTAGE, not in the current into the
coil.
73, Dick, PA0SE
>The output voltage of the TX was somewhat distorted due to harmonics,
>showing up as some ripple at the positive and negative peaks of the
>trace but the zero crossings were at exactly the same points as the
voltage
>over the resistor.
>Thus as far as can be judged from oscilloscope traces voltage and
current
>at the bottom end of the coil were in phase.
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