"Walter Maxwell" wrote:
That was over 40 years ago, but I seem to remember that any
discontinuity that resulted in a VSWR greater than 1.005:1
produced a ghost that could not be tolerated in the transmitted picture.
I'm sure this is the magnitude of reflections Richard F. is referring to.
_____________

Analog TV transmission is not quite that sensitive to VSWR, fortunately.
Matti Siukola of the RCA Broadcast TV antenna group in Gibbsboro, NJ did
some experimental work showing that a 1% reflection (1.02 VSWR) or less is
unnoticeable to a critical observer, a 3% reflection (1.06 VSWR) is
noticeable but tolerable, and a 5% reflection (about 1.1 VSWR) and above is
objectionable. These values applied to the r-f spectrum from visual carrier
(Fcv) to Fcv +2.5 MHz or so, and for transmission line lengths of 500 feet
and more from the tx to the antenna.

These parameters were measured using an r-f pulse at the visual carrier
frequency having the transition times and r-f bandwidth corresponding to the
maximum bandwidth limits of the TV channel, only.

The more conventional broadband TDRs used a very short pulse with energy
from DC to far beyond the limits of the TV channel. It could resolve small
discontinuities along the transmission line, but many of them had no affect
on the quality of the transmitted television image, as they were not present
in the r-f spectrum of the TV signal. And the pulse return of a wideband
TDR is extremely high from the TV transmit antenna itself, which is a DC
short across the far end of the line.

RF (RCA Broadcast Field Engineer, 1965-1980)