JS8Call: Keyboard-to-Keyboard Weak Signal Chat

FT8 gives you 13 characters per transmission. Enough for callsigns and signal reports. Not enough for "hey, how's the weather in Tokyo?"

JS8Call fixes that. Same physics as FT8 (decode signals buried 20+ dB below the noise floor), but with free-form keyboard-to-keyboard messaging. Actual conversations. Questions and answers. Store-and-forward messaging when the other station is offline.

It fills the gap between FT8 (data exchange, not communication) and SSB (requires propagation strong enough for voice).

What Makes JS8Call Different

FT8: Automated exchange. Your computer handles everything. You click a callsign, the software does the rest. Efficient but impersonal.

JS8Call: You type messages. The other person reads them and types back. Like IRC or texting, but over radio, with signals so weak you'd never hear them with your ears.

The protocol is based on FT8's modulation (GFSK, 8-tone, same physics) but modified for continuous text messaging instead of rigid 15-second exchange frames.

Why People Use It

Off-Grid Messaging

JS8Call has a "store and forward" capability. Send a message to a station that's currently offline — it gets relayed through other JS8Call stations until delivered. Like email over HF without Winlink's complexity.

Preppers love this. No internet required. No infrastructure. Two people with HF radios, wire antennas, and laptops can exchange messages worldwide when everything else is down.

Marginal Propagation

Sometimes 20m is "open" but barely. Signals are there at -18 dB SNR. Too weak for SSB. Too weak even to know someone's there without a digital mode. JS8Call lets you have a conversation on those borderline paths that voice operators don't even know exist.

Group Communication

JS8Call supports "groups" — essentially channels. @ALLCALL reaches everyone. @POTA reaches POTA operators. @NET reaches net participants. Directed messaging to specific callsigns works like a DM.

I've seen informal nets on JS8Call where 6-8 stations in different states have a slow-motion text conversation over HF. Each message takes 10-15 seconds to transmit, so it's not fast. But it works on 5W when voice needs 100W+ for the same path.

Automatic Station Information

Your station periodically sends heartbeats — brief transmissions with your grid square and status. Other stations see you on the band without you calling CQ. You see who else is active. It builds a real-time map of the propagation paths available right now.

Setup

Hardware: Same as FT8. HF radio + computer + audio interface (USB cable for IC-7300, Digirig for older radios).

Software: Download JS8Call from js8call.com. Free, open source. Available for Windows, Mac, Linux.

Configuration:

1. Station tab: enter callsign, grid square
2. Radio tab: select radio model, COM port, baud rate (same as WSJT-X)
3. Audio tab: select sound card (same as WSJT-X)
4. Reporting tab: configure APRS/PSKReporter spots (optional)

If you already run FT8 via WSJT-X: JS8Call uses the same audio and CAT settings. Copy them over. Done in 2 minutes.

Frequencies:

• 40m: 7.078 MHz
• 20m: 14.078 MHz
• 30m: 10.130 MHz
• 15m: 21.078 MHz

20m (14.078) has the most activity. Start there.

Using JS8Call

Calling CQ

Click the CQ button. Type nothing else. Your callsign and grid go out automatically. Wait for someone to respond in the RX window.

Directed Message

See someone on the waterfall (their heartbeat decoded)? Type in the message box:

@W6ABC hello from Ohio, how are conditions there?

Hit send. They'll see your message in their inbox. They type back. Conversation happens.

Relay/Store-Forward

If W6ABC isn't online but you want to leave a message:

@W6ABC MSG hey, let's sked on 40m tomorrow evening 7pm local

Other stations running JS8Call in relay mode will store your message and forward it when they hear W6ABC's heartbeat.

APRS Integration

JS8Call can send APRS position reports and messages to the APRS-IS network via RF. Grid square reporting feeds into APRS maps. You appear on aprs.fi via JS8Call without a VHF radio.

The Speed/Distance Tradeoff

JS8Call offers multiple speed modes:

• Turbo: Faster text, shorter range
• Fast: Default balance
• Normal: Good balance of speed and sensitivity
• Slow: Maximum range, very slow text (each character takes longer to transmit)
• Ultra: Experimental, extremely weak signal decoding

Slower = more decoding gain = contacts at lower SNR. For long-path DX on 5W, "Slow" mode can decode signals that "Normal" mode can't.

Most activity happens on Normal or Fast modes. Switch to Slow for extreme-distance attempts.

JS8Call vs FT8 vs SSB

FT8 JS8Call SSB Conversation No Yes Yes Weak signal -24 dB -22 dB Audible (~-5 dB SNR) Speed of exchange 60-90 sec 1-5 min Real-time Automation Full Partial None Human interaction Minimal Moderate Full QRP effectiveness Excellent Excellent Poor

Who Uses JS8Call

• Off-grid/preppers: The emergency communication crowd sees this as the ultimate grid-down messaging system
• QRP operators: Conversations on 5W that voice can't support
• Night owls: Late-night slow conversations on 40m when nobody's on SSB
• Experimenters: Testing propagation paths, relay networks, automated messaging

The community is smaller than FT8 but enthusiastic. Activity peaks on 20m during North American evenings and weekends.

The Honest Take

JS8Call isn't for everyone. The conversations are SLOW. A message that takes 2 seconds to type takes 15 seconds to transmit. A back-and-forth that would take 30 seconds on SSB takes 5 minutes on JS8Call.

But the tradeoff is real: those 5-minute conversations happen on paths where SSB gets nothing. Where FT8 only gives you a signal report. JS8Call gives you actual human connection on the weakest of signals.

If you run FT8 and wish it were more than just clicking callsigns: JS8Call is what you're looking for. Same hardware. Different software. Actual conversations.