On Oct 27, 10:33 pm, (Michael Black) wrote:
Doug Smith W9WI ) writes:

I don't think most amateur TV stations use a VSB lower-sideband filter.
They seem to work OK - though they're generally going for legibility, not
high picture quality!

The other suggestion, that you use a modulator from an old VCR, is a good
one. In America that'll be VHF instead of UHF.

I don't know what's being used nowadays, but it is interesting how it
has been in the past.

Up till 1976, pretty much all articles about ATV would be about high
level modulating an existing transmitter. Do it that way, and the
only way to get VSB is with a filter that can tolerate the power level.

The one exception I've seen was an early sixties article in QST where the
author (a QST staffer if I recall) took the modulated RF output of a
surveillance camera and fed it into an upconverter to get up to UHF.
Likely that wasn't used much since it was more complicated.

Then in 1976, there was an article in "Ham Radio" about modulating
an oscillator running at about 50MHz, and then converting it up
and using a linear amplfication chain. More complicated but likely
put out a better signal than most ATV transmitters at the time. I
seem to recall there was even an LC VSB filter at the "IF" frequency.

I would have thought by now it had switched over to that sort of
thing, but I don't really know.

A lot or most of those RF modulators I've looked at have an SAW
filter, so I assume the output is close to VSB. Feed it into a
mixer stage, then some stages of linear amplification and there
you go.

Michael VE2BVW


I am actually trying to send the output of a video card to a CATV
channel.
I have VGA, S-Video, and RCA TV-out for choices.