How wide is the 8VSB lower sideband?

How wide is the 8VSB lower sideband?
http://www.broadcast.net/~sbe1/8vsb/8vsb.htm

This permissible excess bandwidth is 11.5% for the ATSC 8-VSB system. That
is, 5.38 MHz (minimum bandwidth per Nyquist) + 620 kHz (11.5% excess
bandwidth) = 6.00 MHz (channel bandwidth used). The higher the "alpha
factor" used, the easier the hardware implementation is, both in terms of
filter requirements and clock precision for sampling.

!!!!!!!!!!!!!!!
Note how, like traditional NTSC, the 8-VSB format utilizes a vestigial
sideband approach in the interest of conserving spectrum space. Unlike NTSC,
however, 8-VSB takes this concept to greater extremes: the lower RF sideband
is almost completely removed.
!!!!!!!!!!!!!!

I have not done the math, but I assume 100khz or 200 khz.

On Aug 11, 4:50*am, "Max Power" wrote:
How wide is the 8VSB lower sideband?http://www.broadcast.net/~sbe1/8vsb/8vsb.htm

This permissible excess bandwidth is 11.5% for the ATSC 8-VSB system. That
is, 5.38 MHz (minimum bandwidth per Nyquist) + 620 kHz (11.5% excess
bandwidth) = 6.00 MHz (channel bandwidth used). The higher the "alpha
factor" used, the easier the hardware implementation is, both in terms of
filter requirements and clock precision for sampling.

!!!!!!!!!!!!!!!
Note how, like traditional NTSC, the 8-VSB format utilizes a vestigial
sideband approach in the interest of conserving spectrum space. Unlike NTSC,
however, 8-VSB takes this concept to greater extremes: the lower RF sideband
is almost completely removed.
!!!!!!!!!!!!!!

I have not done the math, but I assume 100khz or 200 khz.

In fact.some receivers can operate even if the suppressed carrier is
missing. Making this very much like SSB instead oif VSB.

Look at p. 12 of this:

http://www.atsc.org/standards/a_53-Part-2-2007.pdf

The pilot (suppressed carrier) is located just before the roll-off
occurs, at the low end of the 6 MHz channel. Contrast this with NTSC,
where the carrier is 1.25 MHz into the 6 MHz band.

Bert

On Mon, 11 Aug 2008 01:50:32 -0700, Max Power wrote:

How wide is the 8VSB lower sideband?
http://www.broadcast.net/~sbe1/8vsb/8vsb.htm

The (mostly suppressed) carrier is 310KHz into the channel in most cases.
I haven't thoroughly studied the standard but I believe almost all of the
310KHz below the carrier is used for lower sideband. (i.e., the LSB
extends nearly to the bottom of the channel, making the sideband 310KHz
wide)

Can't say I'm entirely sure why they bother with a lower sideband at all.

On Aug 11, 11:35*am, Doug Smith W9WI wrote:

The (mostly suppressed) carrier

Sorry, I should have said "attenuated," rather than suppressed.

Can't say I'm entirely sure why they bother with a lower sideband at all.

Probably just to make it easier to filter?

Bert

On Aug 11, 4:50*am, "Max Power" wrote:
How wide is the 8VSB lower sideband?http://www.broadcast.net/~sbe1/8vsb/8vsb.htm

This permissible excess bandwidth is 11.5% for the ATSC 8-VSB system. That
is, 5.38 MHz (minimum bandwidth per Nyquist) + 620 kHz (11.5% excess
bandwidth) = 6.00 MHz (channel bandwidth used). The higher the "alpha
factor" used, the easier the hardware implementation is, both in terms of
filter requirements and clock precision for sampling.

!!!!!!!!!!!!!!!
Note how, like traditional NTSC, the 8-VSB format utilizes a vestigial
sideband approach in the interest of conserving spectrum space. Unlike NTSC,
however, 8-VSB takes this concept to greater extremes: the lower RF sideband
is almost completely removed.
!!!!!!!!!!!!!!

I have not done the math, but I assume 100khz or 200 khz.

Hi Bob!!

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.

SSB is used by hams and military in the shortwave bands for 1 and 2 hop
voice communications (and 3 or 4 hops for data)... but using AM in its place
would make for better multihop communications systems in the HF region. DRM,
the new standard for DAB over SW uses AM modulation with CODFM content. DRM
may kill off the hundreds of SSB based digital [RTTY] transmission systems
used in the HF bands.

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. I don't know
if the ATSC spec supports a stronger carrier, and there is the issue of the
"DC" component inserted into the 8VSB signal 7% of the time to allow
decoders an opportunity to latch onto an unmodulated carrier for PLL or SYNC
decoding.

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.

How wide is the 8VSB lower sideband?
http://www.broadcast.net/~sbe1/8vsb/8vsb.htm

The (mostly suppressed) carrier is 310KHz into the channel in most cases.
I haven't thoroughly studied the standard but I believe almost all of the
310KHz below the carrier is used for lower sideband. (i.e., the LSB
extends nearly to the bottom of the channel, making the sideband 310KHz
wide)

Can't say I'm entirely sure why they bother with a lower sideband at all.

In article ,
"Max Power" wrote:


SNIP

SSB is used by hams and military in the shortwave bands for 1 and 2
hop voice communications (and 3 or 4 hops for data)... but using AM
in its place would make for better multihop communications systems in
the HF region. DRM, the new standard for DAB over SW uses AM
modulation with CODFM content. DRM may kill off the hundreds of SSB
based digital [RTTY] transmission systems used in the HF bands.

SNIP

Bull crap.

--
Telamon
Ventura, California

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

You misunderstand modern (post 1950) SW transmitter design.

Class-B, PDM and PSM (and hybrids of the two) modulators produce an AM
waveform, no matter what.

Some Russian Class-B transmitters can handle transmitting FM, but these are
very pure analog beasts.

Only the modern PDM / PSM / Hybrid transmitters are being put into service
for DRM, no Class-B modulators.

CODFM (as DRM uses it) in the SW bands is a PSUDO-CODFM; the audio of the
CODFM signal is imposed on an AM waveform for transmission. The BSEE
electronics is a lot simpler, and it is backwardly compatible with the
installed base.

Thankfully this DRM AM-CODFM design is so simple that it is totally
misunderstood, and you can't tell the difference at the receiver end.

PSUDO-CODFM aka AM-CODFM
-- CODFM signal is of Audio bandwidth, 10 kHz or 20 kHz
-- Most modern SW transmitters can accept 20 kHz audio with only minor
retrofits
-- Most modern SW transmitters are "linear" up to about 40 kHz, based on 90
kHz PDM / PSM clock rates
-- Most modern SW transmitters only know how to transmit AM +SSB (but not
FM)
-- SW DRM transmitters universally get their PDM / PSM clock rates increased
to 100 kHz + (Continental, retrofit infos)
-- A true wideband CODFM signal of 1 MHz would not work on SW, ITU
allocation issues aside ... the installed transmitters base cannot handle
it, only PSUDO-CODFM is workable
-- VHF / UHF CODFM transmitters are real CODFM transmitters, as there is no
PDM / PSM / etc involved.

There are no true CODFM transmitters in the SW band with powers above 2kw
(or maybe 10kw), as the electrical engineering is just too hard to do.

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.

Max Power wrote:
You misunderstand modern (post 1950) SW transmitter design.

Class-B, PDM and PSM (and hybrids of the two) modulators produce an AM
waveform, no matter what.

Some Russian Class-B transmitters can handle transmitting FM, but these
are very pure analog beasts.

Only the modern PDM / PSM / Hybrid transmitters are being put into
service for DRM, no Class-B modulators.

CODFM (as DRM uses it) in the SW bands is a PSUDO-CODFM; the audio of
the CODFM signal is imposed on an AM waveform for transmission. The BSEE
electronics is a lot simpler, and it is backwardly compatible with the
installed base.

Thankfully this DRM AM-CODFM design is so simple that it is totally
misunderstood, and you can't tell the difference at the receiver end.

PSUDO-CODFM aka AM-CODFM
-- CODFM signal is of Audio bandwidth, 10 kHz or 20 kHz
-- Most modern SW transmitters can accept 20 kHz audio with only minor
retrofits
-- Most modern SW transmitters are "linear" up to about 40 kHz, based on
90 kHz PDM / PSM clock rates
-- Most modern SW transmitters only know how to transmit AM +SSB (but
not FM)
-- SW DRM transmitters universally get their PDM / PSM clock rates
increased to 100 kHz + (Continental, retrofit infos)
-- A true wideband CODFM signal of 1 MHz would not work on SW, ITU
allocation issues aside ... the installed transmitters base cannot
handle it, only PSUDO-CODFM is workable
-- VHF / UHF CODFM transmitters are real CODFM transmitters, as there is
no PDM / PSM / etc involved.

There are no true CODFM transmitters in the SW band with powers above
2kw (or maybe 10kw), as the electrical engineering is just too hard to do.

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.

My head hurts.