"SFTV_troy" wrote in message
ups.com...

Don Pearce wrote:
On Sat, 13 Oct 2007 10:05:11 -0700, "David Eduardo"
"SFTV_troy"


I still don't see the difference. Both standards are using
sidebands, adjacent to the analog AM signal.

DRM is not using a sideband; to do analog and digital requires a
separate
transmitter for each on a separate carrier frequency. HD is a combined
analog and digital signal on the same carrier frequency. DRM is digital
only... if you want analog, you have to have a separate channel, close
to or
not to the DRM one.


Exactly. DRM is a separate signal that can go wherever the operator
chooses. ..... It is not a sideband of the AM.
HD, on the other hand is an actual sideband of the AM carrier.




I see your point, but that seems a trivial difference. Especially
since HD also uses a separate signal (exciter), separate from the
analog signal. "As with AM, FM stations may use separate exciters to
modulate the very different signals." - wikipedia.

On the same carrier for HD, on separate carriers for DRM. DRM is a pure
digital system, and if analog is also employed, it is on a separate
allocation, close or not so close to the digital frequency.