Simple. Because a "Normal" SSB signal doesn't contain enough audio content
below 100Hz or so to
create the effect. I have access to several types of analyzers such as HP (or
Agilent), Rohde &
Schwartz, etc. I work in a very large R&D center for a large mobile phone
company, so I have
access to some top of the line test equipment. I don't constantly monitor with
a $100k analyzer
-- wish I could!! But I do periodically borrow some nice stuff!!
--- Gary Schafer <firstname.lastname@example.org> wrote:
> Hi Joe,
> How would you then explain that this "phenomenon" is not heard or
> perceived as carrier on a normal SSB signal when tuning the signal lower
> in frequency than where the carrier is. This converts the frequencies
> present to even lower frequencies than they actually are. Simulating
> enhanced base but not of the proper frequency for demodulating into
> intelligence of course.
> There are a lot of phase shifts going on in an SSB signal just by the
> nature of the signal.
> I don't know that you will be able to see this stuff on a regular
> spectrum analyzer. Wonder what you have?
> Gary K4FMX
> Joe Isabella wrote:
> > My rig uses DSP generated sidebands. It would be very difficult to create
> > the kind of
> > 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
> > it.
> > However, I will take a closer look at my transmitted signal and see what
> > it's doing on the
> > any...
> > Joe,
> > N3JI
> > --- Gary Schafer <email@example.com> 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.
> >>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.
> >>><<<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.
> >>>Get ready for school! Find articles, homework help and more in the Back
> >>>to School Guide! http://special.msn.com/network/04backtoschool.armx
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