JS8Call
A keyboard chat and messaging mode built on FT8's technology, for slow, robust conversations.
JS8Call sounds like FT8: soft, quiet warbling tones in timed turns, usually starting and stopping together every 15 seconds, with longer messages running over several turns.
What does it sound like?
Like FT8: soft warbling tones in timed turns.
12-second example. Recorded off the air on the developer's own receiver.
Who uses it?
Amateur radio operators, including emergency-communications groups.
Where and when can I hear it?
For example 7.078 and 14.078 MHz.
Hear it live
- University of Twente WebSDR (Enschede, the Netherlands) · 14,078 kHz USB
No schedule; 14.078 MHz is the JS8Call user guide's suggested 20-meter frequency. - Northern Utah WebSDR #2 (Northern Utah, USA) · 14,078 kHz USB
No schedule; 14.078 MHz is the JS8Call user guide's suggested 20-meter frequency.
These are free public receivers run by other people; we only link to them. You'll hear the signal only if it's on the air right now and conditions carry it to that receiver, so if it's quiet, try another time. Links last reviewed 2026-09-28.
The science
JS8Call's radio layer, called JS8, reuses FT8's signal design: eight tones and 79 symbols per transmission. In the Normal speed a transmission lasts 12.64 seconds at 6.25 symbols per second in 50 Hz, while Slow (25 Hz), Fast (80 Hz) and the 40-word-per-minute speed (160 Hz) trade bandwidth and sensitivity for pace. Long messages are split into 75-bit data frames, and a modified Huffman code (a scheme that gives common characters shorter bit patterns) squeezes as much text as possible into each frame.
Why use it?
FT8 carries only short, structured contact messages; JS8Call keeps FT8-style weak-signal robustness, around -24 dB in the Normal speed, but lets people type free-form conversations and messages. It adds directed messages to specific stations or groups, relaying through other stations, automatic acknowledgments and heartbeat beacons that show who can hear whom. The JS8Call-Improved project says it is used daily by emergency-communications, preparedness and off-grid groups.
Lore
Jordan Sherer (KN4CRD) proposed the idea in July 2017 and released it to testers in July 2018 as FT8Call; it was renamed JS8 and JS8Call in October 2018; version 1.0.0 was publicly released on April 1, 2019. JS8 stands for Jordan Sherer designed 8-FSK.
What do the decoded parts mean?
- Messages: Free text, 'heartbeat' signals that say 'I'm on the air', and relayed messages between stations.
Easily confused with
- FT8: FT8 is structured short exchanges on the same clock
How to recognize it
JS8Call borrows FT8's signal design: eight gently stepped tones in a narrow slot about 50 Hz wide at normal speed. So the sound is the same soft, burbling warble. What differs is the behavior. Messages are typed text, so a single message can spread over several consecutive turns, and the band carries periodic "heartbeat" transmissions from stations simply announcing they are on the air.
The program offers several speeds. Normal uses 15-second turns like FT8; faster settings use shorter turns and wider signals, and a slow setting uses longer turns for weaker paths.
Easily confused with:
- FT8: almost the same sound, but on its own frequencies (7.074, 14.074 MHz) and with exchanges that finish in a few turns.
- FT4: shorter 7.5-second turns and a wider, busier sound.
- Olivia: a longer, continuous multi-tone warble without timed turns.
Where and when to hear it
JS8Call activity gathers near the FT8 spots: common dial frequencies include 3.578, 7.078, 10.130, 14.078, 21.078 and 28.078 MHz (upper sideband). It is quieter than FT8, so it can take a while to catch activity, especially outside evenings and weekends.
Emergency-communications and preparedness groups use it for nets and for relaying messages when the internet or phone system is not available, since a message can hop from station to station until it reaches its destination.
Watching the program's activity list is often more revealing than listening. You will see stations sending heartbeats, replying to queries about signal strength, and leaving messages addressed to a group such as @ALLCALL. Like FT8, every station must keep an accurate clock, because turns begin on fixed boundaries of the minute.
A little history
Jordan Sherer, KN4CRD, began the project as "FT8Call" (his design document is dated March 2018), an experiment to turn FT8's robust but rigid exchanges into free-form keyboard conversation. It was renamed JS8Call in 2018. He added store-and-forward messaging, relays and group calls, making it a weak-signal messaging system rather than just a contact-logging mode.
After several years with few releases, development picked up again in 2025, with version 2.3 and then a community-led effort that continues the program today.
Its design choice is a deliberate trade: FT8 gives up free-form text to be as fast and sensitive as possible, while JS8Call keeps most of that sensitivity but spends extra turns so people can say whatever they want.
Common questions
Is it legal to listen to JS8Call?
Yes. It is an open amateur mode, and anyone may receive it. Transmitting requires an amateur license.
How is JS8Call different from FT8?
The radio signal is almost the same, but FT8 sends short, structured messages for quick contacts, while JS8Call carries typed conversation, relayed messages and heartbeats.
Why do JS8Call messages take so long?
Each turn carries only a few characters. A longer message is split across several turns of 15 seconds each at normal speed, trading speed for reliability on weak signals.
How do I decode JS8Call?
Use the free JS8Call program itself, with audio from a receiver tuned to one of the JS8 frequencies. It also needs an accurate computer clock.