Standing waves
On Sep 22, 3:13*am, Szczepan Białek wrote:
Yes. But antennas are in resonance.
That is rarely true.
A naturally resonant antenna has zero reactance at its feedpoint. But
that is not a requirement for it to produce EM radiation efficiently
from all of the r-f current flowing on it.
The monopoles used by MW broadcast stations vary from 60 to 225
electrical degrees in height. Only a few of those heights are
naturally resonant.
Yet they all radiate nearly 100% of the applied power, because any
antenna reactance is offset by an impedance matching network at the
feedpoint.
RF
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