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What is SSB?

Well a very simple answer would be transmitting and receiving on a channel the same as am/fm but using only the upper half of the carrier or the
lower part of the carrier. Or to put it another way.................

Single Sideband modulation (SSB) is a refinement of the technique of amplitude modulation  designed to be more efficient in its use of electrical
power and bandwidth. It is closely related to "Vestigal Sideband Modulation (VSB).
Amplitude modulation typically produces a modulated output signal that has twice the bandwidth of the modulating signal, with a significant power
component at the center carrier frequency. Single Sideband modulation improves this at the cost of extra complexity.
The best way of thinking of SSB modulation is to first consider an amplitude modulated
signal. This will have two frequency-shifted copies of the modulated signal (the lower one is
frequency-inverted) on either side of the remaining carrier wave. These are known as
SideBands, either Upper Sideband (USB) or less commonly Lower Sideband (LSB)

To produce an SSB signal a filter removes one of the sidebands. Most often, the carrier is
reduced (suppressed) or removed entirely. What remains still contains the entire
information content of the AM signal, using substancially less bandwidth and power, but
cannot now be demodulated by a simple envelope detector.

An alternate method of signal generation has been gaining popularity recently in part due to
the availability of low-cost digital signal processor (DSP)systems. To generate an SSB
signal with this method , first two versions of the original signal are generated mutually 90
degrees out of phase, usually by implementing a Hilbert Transformer in a DSP. Each one of
these signals are then mixed with carrier waves that are also 90 degrees out of phase with
each other. By either adding or subtracting the resulting signals, this can generate a lower
or upper sideband signal.

The front end of an SSB reciever is the same as that of an AM or FM receiver, consisting of
a superhetrodyne RF front end that produces a frequency-shifted version of the radio
frequency (RF) signal within a standard intermediate frequency (IF) band.
To recover the original signal from the IF SSB signal, the Single Sideband must be frequency
shifted down to its original range of baseband frequencies, by using a product detector
which mixes it with the output from a Beat Frequency Oscillator (BFO).
For this to work, the BFO frequency must be accurately adjusted. If the BFO is mis-adjusted,
the output signal will be frequency shifted, making speech sound strange and "Donald
Duck" like.

SSB and VSB can also be regarded mathermatically as special cases of quadrature
amplitude modulation
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