Re: VSWR doesn't matter?

"joseph2k" wrote

Poppycock, TV ghosting is caused by multipath length differences. > Calculate > the position ratio and the horizontal scan frequency (15750 Hz is close > enough). That gives you the path length difference; it is generally on > the > order of miles (= major terrain features).

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Analog TV ghosts can be produced within the TV transmit antenna system as well as by reflections of the transmitted signal in the propagation environment. I know this from my experience as an RCA Broadcast Field Engineer, because I've evaluated and corrected many transmit antenna systems that had been the source of such ghosts.

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.