Also known as: FFSK

FFSK (fast frequency-shift keying) is a coherent form of audio FSK in which the mark and space tones are exact integer multiples of the bit rate, so each bit contains a whole number of cycles.¹ This makes detection clean and bit timing easy.

FFSK (fast FSK) is phase-continuous tone signalling used by MDC-1200 and DSC.

How it works

The phase-continuous, integer-cycle tones suit short data bursts over analog FM. FFSK carries MDC1200 unit IDs, DSC maritime calls, and MPT 1327 control signalling, typically at 1200 bps.

Relevance to SDR

GopherTrunk detects FFSK bursts on analog channels to decode signalling such as PTT IDs and trunking control data.

Sources

1. Frequency-shift keying — Wikipedia, for coherent/fast FSK and continuous-phase tone signalling. ↩

See also

• AFSK
• Frequency-shift keying (FSK)
• MDC-1200
• Digital Selective Calling (DSC)
• MPT 1327

Learn it step by step

• Other signals you'll meet