Before FT8 automated the exchange, digital operating meant typing to another person in real time. Those modes are still on the air, and they are the ones to use when you actually want a conversation.
PSK31
A 31.25 baud phase-shift-keyed mode occupying about 60 Hz — you can fit dozens of contacts in the space of one SSB signal. It decodes at low power (25 W is plenty) and shows up as a thin vertical line on a waterfall.
- Common frequencies: 3.580, 7.070, 14.070, 21.070, 28.120 MHz.
- Software: fldigi, WSJT-X's companion tools, or a radio with a built-in decoder.
- Keep ALC at zero — PSK31 is very sensitive to over-driving, which splatters across the segment.
RTTY
Radioteletype: 45.45 baud FSK, dating to mechanical teleprinters. It is inefficient and noisy, and it remains hugely popular in contests because it is fast for exchanges.
- Common frequencies: 3.580–3.600, 7.080, 14.080, 21.080, 28.080 MHz.
- Send either as true FSK (cleanest) or AFSK through the sound card in USB.
- 170 Hz shift, 5-bit Baudot, LSB convention — your software handles this, but the terms show up in
contest rules.
Packet and AX.25
Packet radio puts framed, error-checked data on the air, usually 1200 baud AFSK on VHF or 300 baud on HF. Its heyday was the 1980s and 90s bulletin-board networks, but the protocol underpins two things you will still meet:
Newer conversational modes
- Olivia — very robust, slow, popular on 20 m and 40 m for rag-chewing through noise.
- JS8Call — FT8's waveform with free-form text and store-and-forward relaying.
- VARA — a proprietary high-throughput HF/FM modem used behind Winlink.
All of these need the same station plumbing: audio in and out of a computer and a way to key the radio. See radios and software.