The basic families
- CW — the carrier keyed on and off. Occupies about 100 Hz, and the most power-efficient mode in
- AM — amplitude modulation; carrier plus two sidebands, about 6 kHz wide. Mostly nostalgia and
- SSB — single sideband: one sideband, no carrier. About 2.7 kHz wide, and roughly 8 dB more
- FM — frequency modulation, 10–16 kHz wide. Immune to amplitude noise and excellent audio, but
- Digital — see digital modes.
common use.
aviation now.
effective than AM for the same peak power. The standard for HF voice.
needs a strong signal — hence the sharp "full quieting or nothing" behaviour on repeaters.
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.