On Mar 16, 10:22 am, Cecil Moore wrote:
Richard Fry wrote:
For example, a reflection from a mismatch between a 1,000 foot long,
air-dielectric transmission line and the TV transmit antenna connected
to it
produces a ghost with ~ 2 µs delay from the main image. The active scan
width of an NTSC TV line is about 53 µs, so 2/53 = ~4% of the width of the
screen, or maybe 5% counting overscan. This ghost is easy to see in a
typical TV set/viewing setup.

We performed that exact experiment at Texas A&M
in the 50's. The ghosts were right where the
reflected waves predicted they would be. I
wonder how the modulation in a reflected wave
moves up and down the line without the reflected
wave also moving up and down the line? :-)
--
73, Cecil, w5dxp.com

Awww come on Cecil - think it through...
First the standing wave is only standing by stroboscopic effect, i.e.
the instantaneous alignment (constructive and destructive) of the
forward and reflected wave fronts at a given point along the line...
The currents continue to stream past the standing point (in both
directions) carrying both the carrier and it's instantaneous
modulation products with it...
Also, the ghosts should be multiple... In the example cited of 2 uS
delay, there should be a ghost every 2 uS across the screen, albeit
each subsequent ghost a fixed number of dB weaker that the one before
due to the % radiated (plus line losses) for each round trip...

denny / k8do