Cecil Moore wrote:
Tom Donaly wrote:

Cecil Moore wrote:

Assuming the source signal is sinusoidal, your above assertion
would require non-linearity in the antenna. Since antennas are
generally considered to be linear systems, would you please
explain where the nonlinearity is coming from?


No it wouldn't, Cecil. Even you know better than that. For those who
believe Cecil, consider a lossy transmission line terminated in a
short, or open. The signal is attenuated as it goes down the line, and
also
attenuated as it comes back up the line, in an exponential fashion.
The envelope is thus not sinusoidal.


An attenuated (damped) sinusoidal signal is still sinusoidal, Tom.
The fact that such a signal doesn't generate harmonics proves
that it is sinusoidal. If it were not sinusoidal, it would
by definition, be generating harmonics. Are you really asserting
that a damped sinusoidal signal generates harmonics? That's the
only way to prove it has gone nonsinusoidal.

All non-sinusoidal waveforms contain harmonics of the fundamental
frequency. Every competent engineer in the world is aware of that
technical fact. If the source signal to an antenna is a pure single-
frequency sine wave, and if the standing wave current is non-
sinusoidal, then the antenna has necessarily introduced harmonics,
i.e. the antenna is non-linear.

W7EL is simply mistaken when he says the standing wave current
waveform is not sinusoidal. If the standing wave current waveform
ever was nonsinusoidal, the antenna would, by definition, be
non-linear and be generating harmonics not present in the source
waveform.

Seems you guys need to review your Math 202 course covering Fourier
transforms.

We're talking about the envelope, Cecil, what are you talking about?
Since you've become so enamored of math all of a sudden, go ahead and
plot the current envelope on a length of very lossy transmission line
and tell me, with a straight face, that it follows a sine
function. On the other hand, don't bother. I know it's too hard
on your head, but it's an interesting exercise for everyone else.
73,
Tom Donaly, KA6RUH