Gary Schafer wrote in message
...
On Mon, 02 Feb 2004 21:30:52 GMT, Gregg wrote:

Behold, Michael A. Terrell signalled from keyed 4-1000A filament:

Gregg wrote:

SSB+Carrier is known as vestegial sideband and has an efficiency
somewhere between AM and SSB.

Vestigial sideband is used for the Visual signal in NTSC TV
transmission. The term "Vestigial" comes from the fact that part of the
lower sideband is transmitted to reduce the phase shift caused by the
tuned circuits used to remove most of the lower sideband. In the very
early days of TV they couldn't build accurate filters to remove the
full
lower sideband without causing video problems, so a compromise was made
in allowing a small part of the lower sideband to be transmitted.

Hi Mike,

Quite true! However there were several SW broadcasters experimenting with
VSSB in order to free up the congested SW bands.


Greg,

I think that all are either AM DSB with carrier or SSB with carrier.
There is no reason that I know of to transmit only part of one side
band for broadcast or communications. Other than in TV of course as
was pointed out.

The SW broadcasters use SSB with carrier in order to squeeze into
tighter frequency assignments.

TV stations eliminate part of one side band for the same reason, to
protect the adjacent channel. But they do not abruptly eliminate the
video signal because of the phase shifts caused in the filtering. This
is where the vestigial side band comes in.

73
Gary K4FMX

If I recall correctly, the SW Broadcasters were going to use SSB with
reduced carrier, around 12 db down from normal level.