Brenda Ann wrote:
wrote in message
ups.com...
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.
No arguments from me. That was how I was taught in college, though ISB
was never a topic.
ISB (with carrier) has been around for a while. It was used in one of the
original AM Stereo experiments. I believe it was Kahn that was using it. The
only station I know of personally that used it commercially was XETRA, and
it actually didn't do too badly, but you needed either a special receiver or
two radios to tune the two sidebands to receive stereo. It was not a
compatible system though in the sense that on a single standard AM radio,
you only heard the channel (perhaps with some spillover depending on tuning)
that the radio was designed to demodulate.
When you study communications in a university, it tends to be pure
theory rather than some specific protocol. While this seems
counter-intuitive, understanding the theory means you can figure out
some proprietary standard when the time comes. The only exceptions that
come to mind would be something like duobinary modulation, which I
think was a GTE patent, though it was treated as something generic. So
getting back to ISB, it never came up, though by your description it is
a matter of pulling out the sideband independently. So if you
understand SSB, ISB would follow.