Doug McDonald wrote:
As Doug McDonald suggests, you can detect the *presence* of a DTV signal
by looking for the carrier. It's 310KHz above the bottom of the channel
- for example, 476.31MHz for a DTV station on channel 15. Unfortunately
you can't tell *which* DTV station you're receiving the carrier from...

Is that clear, or are there frequency offsets that can be used?

A limited number of channel allocations are marked with "c" in the
table. This requires their carrier to be offset by some specific value
(with five significant figures which I can't remember...) from an
adjacent-channel analog station. I would suppose that means their
carriers may be 300 or 320KHz up depending on the offset of the analog
station.

There are very few such allocations - none here in the Nashville area.

Yes. A transmitter is easier than a receiver. You just need to
feed it the MPEG encoded stuff, which is the same in Europe or
the US (except of course the vertical frequency).

Their designs included the MPEG encoder.
http://www.von-info.ch/hb9afo/datv_e.htm
http://www.datv-agaf.de/
(latter site mostly in German. It indicates they're selling the cards
for amateur applications for "slightly higher costs" than 750 euros.
(roughly equivalent to $750))

If I read things properly - and I may not - these cards are capable of
generating an ATSC-compatible 8VSB signal from an analog NTSC input.
Probably no PSIP though which could be a problem with most receivers.

They're using satellite receivers, sometimes with preamps attached, for
their receivers.
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com