My rig uses DSP generated sidebands. It would be very difficult to create the
kind of situation
you suggest. But as you have audio content closer to the carrier point, the
receiving station
percieves it as a carrier while tuning through because of relative closeness of
this content to
it.
However, I will take a closer look at my transmitted signal and see what it's
doing on the spec
any...
Joe,
N3JI
--- Gary Schafer <garyschafer@comcast.net> wrote:
> The "carrier" that you hear on these signals is probably not carrier but
> inband IM products from the low frequency audio signals. Listen closely
> and you will see that it is only present with modulation.
>
> As to opposite side band suppression, with a filter, the low frequencies
> are not attenuated by the filter as much as the higher frequencies.
> Because they are closer to the pass band of the filter. Not as far down
> the skirt. So more get through on the unwanted side band. Especially
> when the base is boosted.
>
> With a phasing type of side band generation the problem comes from
> inadequate phase linearity at the low frequencies. Then add in the
> inband (audio) IM products and the apparent side band suppression really
> gets bad.
>
> No I am not an advocate of limited bandwidth either. Experimentation is
> great. There are more "better" sounding stations on the air as a result
> of the experimentation. It has a ways to go as far as being "clean" but
> it is no worse sounding than some of those awful appliances with
> "special" microphones designed to "cut through the qrm". They can make
> your ears bleed.
>
> 73
> Gary K4FMX
>
>
> Rob Atkinson, K5UJ wrote:
> > Not at all. Why? A. the > 3 khz guys are almost all using digital
> > phase cancellation methods for sideband generation therefore there is no
> > carrier and no opposite sideband to suppress.
> > B. The few who are using 6 khz xtal filters (actually a little
> > less--5.8 khz) and analog method are using rigs with front panel
> > adjustable microprocessor controlled carrier set points that allow them
> > to place the carrier at least 200 hz below the -6 db filter skirt point
> > so it is way way down the skirt; the opp. s.b. even farther away. Oh
> > sure, there may be a few hams who are attempting this with the wrong
> > gear and don't know any better. Anything's possible. Are mistakes,
> > booboos and a learning curve now forbidden? I guess it's time for all
> > rigs to be contained in solid epoxy blocks before being sold to us.
> > Didn't know experimentation was taboo.
> >
> > Rob/K5UJ
> >
> > <<<Having bass that extends well below 100hz will cause a SSB signal to
> > be wide by modulating too close to the carrier point, crossing over
> > onto the other sideband, and virtually turning into a DSB signal If you
> > don't believe this just try tuning a "hi-fi" guy in on using the AM
> > mode. The signal will be 100% intelligible!! You can even hear the
> > carrier when you tune across one of these signals. Plus the fact when
> > one tries to force over 10db of extra energy at very low or very high
> > frequencies the IMD is terrific and that also contributes to the width
> > of the signal.
> >
> > WY3D>>>
> >
> > _________________________________________________________________
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> > to School Guide! http://special.msn.com/network/04backtoschool.armx
> >
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>
>
>
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