View Single Post
  #96   Report Post  
Old May 24th 04, 08:05 PM
Richard Fry
 
Posts: n/a
Default

Cecil Moore quote below & 'steady state'

The transmitter is continuously generating incident power, which is
continuously subject to reflection(s) by any mismatch in the antenna system.
Given the right magnitude, phase and time displacement, each reflection will
produce a continuous ghost on the TV screen.

These ghosts can be seen (continuously) in/on the output waveform of a TV
demodulator connected at the output of the transmitter -- both in time
domain on an oscilloscope, and visually on a monitor. I've seen these
continuous reflections scores of times at TV tx sites all over the US as a
field engineer for RCA Broadcast Division.

"Conventional wisdom" on this NG may say otherwise, but hopefully some may
learn the reality from this exchange.

- RF
____________________

"Cecil Moore" wrote in message
...
Richard Fry wrote:

TV Ghosting (quotes below)

To elaborate, the visibility of a ghost image in analog TV systems is
related to the magnitude, phase and time displacement of the RF

reflection
that produced it as compared to the original, or non-reflected waveform.

The round-trip transit time from the TV tx output to the mismatch in its
antenna system will determine the time displacement of the ghost, at the
rate of 1 microsecond of displacement per ~490 feet of distance between

the
tx and the reflection plane (vp = 0.997c).


Richard, you know you are going against the conventional wisdom on
this newsgroup. Ghosting cannot exist during steady-state so if
ghosting exists it simply means that you are still in the transient
state and the steady-state doesn't exist (yet).