alhearn wrote:
Take the case of a transmitter and an antenna connected together with
a two-port black box between them, and that black box happened to
contain a transmission line. That unseen transmission line has
standing waves and reflections (assuming a mismatched condition),
losses, etc. all contained within the box. However, the transmitter
only sees a steady state complex impedance when looking into the box
(at a single frequency).

That's a steady-state shortcut which assumes pure sine waves that
don't exist in reality. Please don't confuse steady-state shortcuts
with reality. Noise and modulation cause the "steady-state complex
impedance" not to be steady-state at all. Many will say it's close
enough, but one cannot understand reflections by assuming an un-
varying steady-state.

In a TV system with ghosting due to reflections, the unvarying steady-
state condition doesn't exist. In fact, when you assume steady-state
conditions, you eliminate ghosting, at least in your own mind. In
reality, steady-state doesn't really exist because of random noise
and unpredictable modulation.
--
73, Cecil http://www.qsl.net/w5dxp



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