JS8

JS8 is keyboard-to-keyboard chat on FT8’s waveform, on the air compatible with JS8Call: the same four speeds, the same heartbeats, directed messages, relays and store-and-forward inbox, so a JS8Call station and a Nexus station work each other without either knowing the difference. It is a ragchew mode, not a contest mode — a short exchange takes a few periods, a paragraph takes a minute — and it is the mode of choice on 40 and 20 m when the band is too poor for voice and FT8’s canned exchange is not a conversation.

Before you start. JS8 is on out of the box — look in the Digital group of the rail, after APRS. If you don’t operate it, switch it off in Settings ▸ Appearance ▸ Features. Entering the screen tunes the rig to the JS8 watering hole for the current band (7.078, 14.078, 3.578 … — JS8Call’s own list, USB) and starts decoding every speed at once. Nothing transmits until you enable TX in the header, every session. The mode’s own switches — transmit speed, which speeds to decode, heartbeat interval, the three automatic-reply switches, the idle watchdog and your INFO/STATUS/group texts — are in Settings ▸ Digital ▸ JS8.

The tour

The header. A JS8 badge, then the four speed chips — Slow · Normal · Fast · Turbo (30 / 15 / 10 / 6 second periods); the lit one is the speed you transmit at and the period the TX clock follows. Beside them an RX ▼ n/4 plate says how many of the four speeds the receiver is decoding right now (all four by default). Then the band picker with the JS8 watering holes, license-filtered per band; a Drive slider (TX audio level — set it so the rig’s ALC barely moves); Tune; an ATU button when your rig reports a tuner; the TX On / TX Off latch; Stop TX; and ⊞ Panels.

The waterfall. Click sets your RX offset, right-click your TX offset, Shift-click both. JS8 stations sit anywhere from 500 to 2500 Hz; heartbeats cluster in the 500–1000 Hz sub-band by convention.

The panes (each removable from ⊞ Panels):

• Activity — every frame decoded at every enabled speed, one row each: UTC, the speed letter (E Slow · A Normal · B Fast · C Turbo, JS8Call’s ALL.TXT letters), the audio offset, the SNR, and the message exactly as JS8Call would print it. Rows addressed to you carry a bar; your own transmissions are tinted; faint rows are low-confidence copy; italic rows closed without their last frame. Double-click a row to write to that station.
• Stations — everyone heard, with grid, SNR, offset, speed, age, and chips for a recent heartbeat, a recent CQ, and any messages you hold for them. Click a callsign to address it; the five quick buttons send SNR? · GRID? · INFO? · HEARING? · QUERY MSGS to that station, which answers by itself if its auto-reply is on.
• Inbox — messages addressed to you, and MSG TO: messages you are holding for someone else until they collect them (store and forward). Mark read, delete.
• Log — the log strip, prefilled from the station you last addressed. A JS8 QSO logs as MFSK / JS8 in ADIF.

The TX dock, pinned under the panes. The To box (blank = everyone, a callsign, @ALLCALL, or a @GROUP you belong to), the composer, a frame estimate (“3 frames · 45 s”) and Send; a command palette with JS8Call’s 32 directed commands; the CQ variant picker and CQ; HB; the AUTOREPLY · RELAY · HB ACK chips; the pending auto-reply row with its countdown and Cancel; the queue with Drop queue; and the idle-watchdog readout.

Receiving

All four speeds decode at once, exactly as JS8Call’s multi-decode does: a Slow station at −26 dB and a Turbo station rattling off a paragraph on the same band both print. Untick speeds in Settings if a small machine struggles. A long message arrives one frame per period and is stitched together by audio offset — you see the frames arrive in Activity, and the finished message in Inbox if it was for you.

Transmitting

JS8 keys one frame per period, every period, with no even/odd parity — a 60-character message at Normal is five frames, 75 seconds. Send queues the frames; the next period boundary sends the first. Plain text (no addressee) goes out prefixed with your callsign, so every frame identifies you.

Everything automatic is gated twice. The first act is the TX On latch in the header — never remembered across launches. The second is the switch for that kind of transmission: AUTOREPLY (answers SNR?, GRID?, INFO?, STATUS?, HEARING?, QUERY MSGS addressed to you), RELAY (passes on messages routed through your callsign and holds MSG TO: traffic), HB ACK (answers heartbeats with your report) — those three persist in Settings, at JS8Call’s defaults (on, on, off) — and HB, the heartbeat schedule, which is session-only. A chip that is on while TX is off shows it plainly, and nothing keys. Every automatic reply first sits in the dock for one period with a countdown and a Cancel. After an hour with nothing typed (the idle watchdog; adjustable), heartbeats, auto-reply and relay switch themselves off and the dock says so.

Stop TX (header, or Esc anywhere in the screen) cuts the frame on the air, empties the queue, cancels a pending reply and stops the heartbeat schedule. Drop queue only empties the queue — a frame already on the air finishes. Turning TX Off lets the frame in flight complete, as in the FT8 screen.

Compatibility

On the air: JS8Call 2.2 and later, and JS8Call-improved, at Slow, Normal, Fast and Turbo. Not implemented: the “JS8 60” / Ultra speed (compiled out of JS8Call itself), and the APRS-IS and @JS8NET internet gateways. The full protocol reference is JS8Call’s source, read as the specification; see NOTICE.