Tom wrote:
wrote:
Michael Black wrote:

I glanced at it and maybe missed something, but DSB is AM. And
he certainly says it at the outset, and when he's talking about the
components he's talking about 2 sidebands and a carrier.

Now, "DSB" often has fallen into the meaning of "DSB with no carrier",
but technically one should specifically define that there is no carrier.
snip
Michael

Back in 1972 when I took my FFC 2nd and 1st class exams DSB was defined
as the sidebands with a supressed carrier. A signal with both sidebands
and the
carrier was simply AM with a BW disgnator. .Now that diffintion may
have slipped
over the years, but from my perspective AM means both sidebands, with a
carier
DSB means both sidebands without the carrier, and ISB means two
different
sidebands with no carrier. I only have received the later, ISB, a very
few times
mainly on ancient STL links.

It might be useful to check out what the ITU says these days about
"AM", both sidebands with carrier", and for this conversation, "DSB"
being both sidebands without the carrier.

Terry

That high authority, Wikipedia, at http://en.wikipedia.org/wiki/DSB
says, "in telecommunications, double-sideband transmission - see also
double-sideband suppressed-carrier transmission (DSB-SC) and
double-sideband reduced carrier transmission (DSB-RC)".

That is supported by ATIS Telecom Glossary 2000 (ANSI approved) at
http://www.atis.org/tg2k/ : "DSB: Abbreviation for double sideband. See
double-sideband transmission." --- "double-sideband (DSB)
transmission: AM transmission in which both sidebands and the carrier
are transmitted." and "DSB-SC: Abbreviation for double-sideband
suppressed carrier. See double-sideband suppressed-carrier
transmission." --- "double-sideband suppressed-carrier (DSB-SC)
transmission: Transmission in which (a) frequencies produced by
amplitude modulation are symmetrically spaced above and below the
carrier frequency and (b) the carrier level is reduced to the lowest
practical level, ideally completely suppressed. Note: DSB-SC
transmission is a special case of double-sideband reduced carrier
transmission."

Accordingly, DSB=AM unmodified and AM is the essential first step for
its modified variants SSB, ISB, DSB-SC/DSB-RC.

Tom

I guess that diffintions aren't static, er fixed.
Thanks for the clarification.

Terry