Olivia MFSK

Also known as: Olivia, Olivia MFSK

Olivia (often written Olivia MFSK) is an amateur HF text mode built for the worst conditions — deep fading, static, and interference — where it can copy full sentences of error-free text several decibels below the audible noise floor. It sends characters as one of many tones (M-ary FSK) wrapped in a strong forward-error-correction block, trading raw speed for extraordinary robustness.¹ Where plain RTTY collapses in a flutter, an Olivia link keeps delivering clean text.

Each character becomes a Hadamard codeword; its bits are spread over several MFSK tones, so noise that kills one tone rarely defeats the codeword.

Overview

Olivia is described by two numbers, tones/bandwidth — e.g. 8/250, 16/500, or 32/1000. The first is the number of MFSK tones, the second the channel width in hertz. More tones and narrower spacing make the link slower but more sensitive. Each 7-bit ASCII character is turned into a 64-bit Walsh/Hadamard codeword; those bits are interleaved and scrambled across a block of MFSK symbols so that a burst of noise damages many codewords slightly rather than any one fatally. The receiver correlates the received tones against all possible codewords and picks the best match, which is what lets it work under the noise.

Technical characteristics

Property	Value
Modulation	MFSK, 2–256 tones
FEC	64-bit Walsh/Hadamard block code
Common variants	8/250, 16/500, 32/1000, 8/500
Throughput	~1–150 characters/min (mode-dependent)
Sensitivity	Copy at roughly −14 dB SNR (2.5 kHz)
Carrier	SSB audio, HF

Variants

The tones/bandwidth pairs form a family: fast, wider modes for good conditions and slow, narrow modes for marginal paths. Because so many combinations exist, operators usually agree on a standard set (32/1000 and 16/500 are common calling modes). A related mode, Contestia, was derived directly from Olivia with a smaller character set and lighter FEC for a bit more speed.

History

Olivia was designed in 2003 by Pawel Jalocha (SP9VRC), who set out to beat RTTY on poor HF paths using ideas from spread-spectrum and coding theory. It quickly became a staple of HF digital chat and weak-signal experimentation, supported by Fldigi and similar sound-card software.¹

Deployment

Olivia is an amateur-only mode used for keyboard-to-keyboard QSOs on HF, with informal calling frequencies on 20, 30, and 40 metres. It is popular for reliable text exchange across long, noisy paths where speed matters less than getting the message through.

Decoding it with GopherTrunk

GopherTrunk does not decode Olivia. It is an HF amateur text mode outside GopherTrunk’s land-mobile trunking scope; Fldigi and MultiPSK are the usual decoders. GopherTrunk does implement the underlying primitives Olivia leans on — MFSK tone detection and block FEC — but not this protocol’s framing.

Sources

Olivia MFSK — Wikipedia, for Olivia’s MFSK-plus-Hadamard structure, tones/bandwidth variants, sensitivity, and origin. ↩ ↩²