Single sideband
| Single sideband (SSB) | |
|---|---|
| Mode type | Voice; amplitude modulation with the carrier and one sideband removed |
| Bandwidth | About 2.4–2.8 kHz |
| Where used | Nearly all HF voice; weak-signal VHF and UHF |
| Convention | Lower sideband below 10 MHz, upper sideband above (and on 60 m) |
| Calling frequencies (US) | |
| 20 m | Voice segment 14.150–14.350 MHz |
| 2 m | 144.200 MHz |
| 6 m | 50.125 MHz |
Single sideband, or SSB, is the voice mode used on almost all HF amateur contacts. It is a refinement of amplitude modulation: an AM signal carries the same information twice, in two mirror-image sidebands on either side of a carrier, and SSB transmits only one sideband and no carrier. The result occupies less than half the bandwidth of AM and puts all of the transmitter's power into the part of the signal that carries the voice. That efficiency is why a 100-watt SSB station can be heard across the world.
Upper and lower
Either sideband can be used, and the choice is a convention that everyone follows so that receivers are set the same way. Below 10 MHz, hams use lower sideband (LSB): the 40-meter, 80-meter and 160-meter bands. Above 10 MHz they use upper sideband (USB): 20 meters, 17, 15, 12 and 10 meters, and all VHF and UHF SSB work. The 60-meter band is the exception, where USB is required by rule. Modern radios pick the conventional sideband automatically when you change bands.
Tune an SSB signal with the wrong sideband selected and you hear "Donald Duck" gibberish; with the right one but slightly off frequency, the voice sounds too high or too low. SSB tuning is done by ear, a few tens of hertz at a time, until the voice sounds natural.
Operating
SSB contacts range from brief exchanges of signal reports with a rare DX station to hour-long ragchews. Signal reports are given as two numbers, readability 1–5 and strength 1–9, so "59" means perfectly readable and very strong, and "five by nine" is the standard pleasantry even when it isn't quite true.
Because SSB has no carrier, the transmitter only puts out power when you speak, and speech peaks matter. A speech processor or compressor raises the average power without raising the peaks, which helps a weak signal be understood. Over-driving the microphone splatters across neighboring frequencies and is the most common bad habit on the bands.
On VHF and UHF
SSB is also the weak-signal mode on the 2-meter band, 70 centimeters and 6 meters. With a horizontal Yagi and a hilltop, 2-meter SSB contacts of 200 miles are routine and far more is possible during tropospheric openings. The calling frequencies are 144.200 MHz, 432.100 MHz and 50.125 MHz.