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.
Specifications
The public technical record.
Read how JSQ services work and how OpenJSQ encodes them on the air.
Start here to operate · 1.0.0
OpenJSQ operator guide
Station preparation, the setup wizard, HF and VHF/UHF quick starts, every app page, waveform choices, troubleshooting and important defaults.
The four core specifications.
How messages are encoded
JSQ Public Protocol Specification
1.6-draftAX1200 · FSQ
6 September 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 v0.6FM · HF · not frozen
14 September 2026
Two implemented formats: FM modes JG1200–JG2400 and HF SSB modes H600/H900/H1200. Covers the waveform, ASCII/JHAT, 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
JG25 v0.6 was refreshed on 14 September 2026 from application commit 14e3a49, adding the implemented HF format alongside FM. The other protocol snapshots retain their earlier revisions. 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- JG25 v0.2 (superseded design draft)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.