SSB - Single SideBand

It is a modulation method similar to AM, in which the carrier and one of the sidebands are not transmitted.
This way the transmitter can be used very efficiently (more than double the power, with the same components), the reception sensitivy is higher and the bandwidth is less than the half.
For these reasons SSB is the phone system of choice for radio amateurs, on all frequencies, from HF to microwaves, even if it requires complex, and thus not cheap, equipment.
For a good SSB reception, tuning must be perfect, or the voice would be heard with an innaturally high (or low) pitch.
Depending on wether the upper or lower sideband is transmitted, we can have the USB or LSB mode.