11.2.3 - THE SINGLE SIDEBAND REVOLUTION

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 of 1950”s.
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 modulated receiver.
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 system.
TERMINOLOGY TRANSMITTER STAGE TERMINOLOGY RECEIVER STAGE
A MICROPHONE J TUNER
B LOW FREQUENCY CARRY OSCILLATOR L I. F. AMPLIFIER
C BALANCED MODULATOR M MIXER
D AUDIO AMPLIFIER N BEATING OSCILLATOR
E SSB FILTER O SSB FILTER
F BALANCED CONVERTER P NARROW BAND I. F. AMPLIFIER
G CARRIER OSCILLATOR Q DEMODULATION OSCILLATOR
H LINEAR POWER AMPLIFIER R PRODUCT DETECTOR
I LINEAR AMPLIFIER S AUDIO AMPLIFIER
    T LOUDSPEAKER

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.