Modulation and modes

The basic families

• CW — the carrier keyed on and off. Occupies about 100 Hz, and the most power-efficient mode in

common use.

• AM — amplitude modulation; carrier plus two sidebands, about 6 kHz wide. Mostly nostalgia and

aviation now.

• SSB — single sideband: one sideband, no carrier. About 2.7 kHz wide, and roughly 8 dB more

effective than AM for the same peak power. The standard for HF voice.

• FM — frequency modulation, 10–16 kHz wide. Immune to amplitude noise and excellent audio, but

needs a strong signal — hence the sharp "full quieting or nothing" behavior on repeaters.

• Digital — see digital modes.

Bandwidth versus robustness

Narrow modes concentrate power and get through noise; wide modes sound better when the signal is strong. That trade-off explains the entire mode landscape: CW and FT8 for marginal paths, SSB for normal HF work, FM for strong local signals.

Sideband convention

Lower sideband below 10 MHz, upper sideband above it, and always USB on VHF/UHF and 60 m. Convention, not regulation, but universally followed.

Signal quality

• Splatter comes from overdriving; watch ALC and speech processor levels.
• Key clicks come from too-abrupt CW keying envelopes.
• Overdriven digital is the most common modern offence — turn the drive down until ALC barely

moves.