The idea of the Single Sideband
first surfaced in 1915. In the later twenties translatantic
telephone SSB transmission over submarine cable was in opeation.
In 1936 engineers at Western Electric built a high frequency
SSB receiver that used a series of electric motors to keep
the BFO frequency.
However, it was Arthur Collins and his engineers, which brought
this new type of transmission to reality in the beginning
Originally in the SSB system, the carrier and one sideband
are removed in such way only the transmitter radiates the
remaining sideband. Some SSB system, include facilities to
injecting a controlled level of carrier when desirable, so
either a pure SSB signal or a SSB signal with a controlled
amount of carrier can be radiated.
Thus, when necessary the carrier can be inserted, with a level
just high enough to permit demodulation by standard amplitude
Since only one sideband is is radiated and because of the
higher frequency stability required, the guard bands need
not be as wide as for the transmission in amplitude modulation.
In this way the obious feature of SSB transmission was the
improvement the radiofrequency spectrum space either for radio
amateurs as well as crowded communciation channels.
Using SSB system solved several communciation problems regading
economy, reliability and operational versatility. In the later
fifties radio amateurs, military services and airborne communication
systems were operating with SSB equipments. Fig 298
|Fig. 298 - Schematic SSB transmission
||LOW FREQUENCY CARRY OSCILLATOR
||I. F. AMPLIFIER
|| BALANCED CONVERTER
||NARROW BAND I. F. AMPLIFIER
|| DEMODULATION OSCILLATOR
|| LINEAR POWER AMPLIFIER
|| PRODUCT DETECTOR
|| LINEAR AMPLIFIER
|298A - SSB radio receiver model 2B made
in the USA by R. L.Drake.
The SSB concept started a revolution in the global communications
system. As aforeseen since the beginning the improvement of
wireless transmission was deeply related with the perenial
contribution of radio amateurs culminating in the 1950’s
with the SSB system and certainly with the mobile radiotelephony.