Hi!

Before the advent of mandatory digital over-the-air TV, it was
said that the picture would be near perfect, and that there
would be no ghosts.

Ghosts in a digital over the air TV signal won't be caused for the
same reasons that analog over the air TV signals had them.

What's going out over the air in a digital TV transmission is a data
stream, complete with some degree of error correction. Any such
"ghosting" would show up in the signal as a duplicated datastream,
which is probably ignored or considered errant by the video
decompressor in the unit. If you were to get enough of these, you
might notice some glitching ("checkerboard pattern") in the video.

When you receive digital TV broadcasts, they will be an all or nothing
affair. Either you are receiving enough of the datastream to receive a
picture and sound, or you are not.

Tonight I saw one, for a full half hour if the scene had the
right kind of lines, including vertical lines.

The flaw could have been in the material being broadcast. No
broadcasting method can make up for flaws in the original material.
Older material is more likely to suffer from problems.

It sounds like you have a significant length of cable between your
converter box and TV set, going to a significant number of places and
through some amplifiers. If you are looking for interference, you are
looking there. But I don't think you'll find any--or at least not
much. In other words, this isn't the ideal situation, but I doubt it
is the problem.

Everything after the converter box's RF output is an analog TV signal
and therefore subject to the same things that can interfere with a
much more powerful analog TV broadcast signal.

The only major thing I don't like about digital TV is the
unwatchability of weak signals. Watching weak analog TV signals was
never much fun, but at least it was doable if you had to.

William