On Aug 12, 2:18*am, "Max Power" wrote:

With shortwave broadcasting [where your carrier can almost vanish but the
sidelobes may remain relatively intact for PLL or SYNC detection] *...
throwing away the sideband has had mixed success for the international
broadcasting sector. International broadcasters tried "compatible SSB" (in
the 1990s) and it did not work.

Don't know about compatible SSB's success or lack thereof, but I did
hear some SSB experimental transmissions years ago, in the SW band, I
think from Radio Cuba. They sounded fine, although the AM transmission
that was simulcast had better audio quality. More low frequency
content.

DRM,
the new standard for DAB over SW uses AM modulation with CODFM content.

DRM, Digital Radio Mondiale, uses COFDM, as does the European VHF and
L-band DAB system and the US HD Radio. COFDM, in its multiple
subcarriers, does not use AM. Instead, each subcarrier is modulated
with an orthogonal QAM. So that's a modulation in which both amplitude
and phase are varied at the same time, to carry twice as much
information as an AM signal of the same bandwidth can carry.

In my view, having a carrier that is 1.5db stronger than the rest of the
signal would work for 8VSB (in UHF and VHF TV service) ... but I would never
agree with getting rid of the sideband entirely. SSB (with no sideband) may
be spectrally efficient ... but horribly expensive to decode.

It's not that expensive to decode. As a matter of fact, at least some
ATSC receivers are capable of locking onto a signal even if the pilot
is gone. Which makes the signal in every way SSB. The main reason for
that vestigial lower sideband, in 8-VSB, as far as I can tell, is to
ensure that the pilot and the lowest frequencies of the upper sideband
are not clobbered by a sharp cutoff filter. I don't believe the
vestigial sideband serves any other purpose here.

In summary 300 kHz for a sideband is a small spectral price to pay for ~19.5
mbs link that does not lose sync so easily.

I can agree with that.

Bert