What the services mean
JSQ Transport Service Specification
1.0-draftService model
19 August 2026
The rules above the modem: chat, mail, files, presence and relay; capability discovery; and the meaning of sent, stored, acknowledged and delivered.
Operator help & technical specifications
Choose the right level of detail.
JSQ is a multi-modem messaging transport, not merely a new waveform. Its common services are carried across FSQ, AX1200, and JG25, with simultaneous audio receive and incoming-mode automatic replies. Just getting started? Use the operator guide; developing an implementation? Explore the on-air specifications.
Need a hand with your station?
Ask in Getting Started & Support, report a bug, or suggest a feature on the community forum.
Start here to operate · 1.0.9
OpenJSQ operator guide
Station preparation, the setup wizard, HF and VHF/UHF quick starts, every app page, waveform choices, multi-receive across enabled waveforms over radio audio, troubleshooting and important defaults.
The four core specifications.
How messages are encoded
JSQ Public Protocol Specification
1.11-draftAX1200 · FSQ
9 October 2026
The wire representation of JSQ services, including packet types, file automatic repeat request (ARQ), mail custody, presence, relay and delivery receipts.
How FSQ carries the signal
FSQ Fast Public Technical Specification
1.0-draftFSQ · FSQ Fast
19 August 2026
The 33 tones, exact rates, scaling rule, registered profiles, text coding, framing, cyclic redundancy checks (CRCs) and test vectors.
How JG25 carries the signal
JG.25 Native Digital Link Specification
Experimental Draft v0.9FM · not frozen
9 October 2026
The native FM modes JG1200–JG2400, waveform, protected header, framing, error protection, and shared JSQ service envelope.
Public technical documentation; not RF-emission certification.
Compatibility, evidence and design.
Protocol compatibility
The classic FSQ compatibility contract against the selected fldigi version and original FSQ documentation.
JG25 evidence notes
Distinguishes specified waveform rates, scoped decoder results and radio qualification still to be completed.
How JG25 was chosen
The simulations, rejected approaches, receiver changes and real-radio de-emphasis discoveries behind the FM waveform.
Specification conformance review
A section-by-section check of published on-air claims against the transmitting code.
Previous versions and revision history
The public protocol specification (1.11-draft), JG25 (v0.9), the transport service specification, the FSQ Fast specification and the compatibility document were refreshed on 18 October 2026 to match OpenJSQ 1.0.8. Since the 9 October snapshot the protocol specification and JG25 gain three additions describing OpenJSQ 1.0.7 behaviour: the awaiting approval status of a shared-file download, how a heard list and a signal report travel through a relay, and the name a mail attachment travels under. Earlier site snapshots remain available as Markdown:
- JG25 v0.5 (previous FM specification)
- JG25 v0.2 (superseded design draft)
- JSQ protocol 1.5-draft
- JSQ transport, previous snapshot
- FSQ Fast, previous snapshot
JG25 evidence notes distinguish specified waveform rates, decoder research and radio tests that still remain to be completed.
Documents keep stable addresses and earlier revisions remain available. Stable public availability. Small numbered references, such as Transport 0, take you straight to the section supporting a claim.