The adapter and radio link
FSQ
FSQ carries the file. Its speed and radio conditions determine how long the transfer takes.
FSQ details →JSQ transport · the idea
Build the services once.
Choose the modem
for the path.
JSQ puts conversations, mail, files, and network services in a shared transport layer above the modems. The services are implemented once. Different supported radio links carry them.
A service architecture for digital radio—not another waveform or a particular application.
Separate services from signals
The services live
above the modem boundary.
When services are tied to a waveform, choosing its features means accepting its radio limits. Choosing a more sensitive link can mean giving up features you need. JSQ separates those choices with a shared service layer above the modems.
Waveform-centered design
Separate service stacks
- Mode AChat · Files · Relay · DiscoveryFaster text · Lower sensitivity
- Mode BMessaging · Mail · Relay · DiscoveryWeak signal · Slower text
- Mode CChat · Mail · Files · DiscoveryConnection required · Proprietary modem
Choose the features.
Accept that mode’s limits.
The JSQ approach
One shared service layer
Choose the link.
Keep the shared services.
Example link details and sources
Mode A: connectionless, HF/FM. Top text speed ≈60 WPM. Estimated HF minimum SNR: −17 dB at 20 WPM; −14 dB at top speed. The illustrated file service lacks whole-file verification. Rate and sensitivity table →
Mode B: connectionless, HF. Normal speed ≈16 WPM at an estimated minimum SNR of −24 dB. Mail can be stored at an intermediate station. User guide →
Mode C: connected chat through a proprietary modem, HF/FM. Speed adapts to the link, bandwidth, and license. Its low-rate HF broadcast reference is 18 bit/s at ≈−21 dB SNR; this is not a guaranteed threshold for maintaining a connected chat. Low-rate broadcast figures →
Rates and sensitivity describe specific profiles, not a controlled comparison or guaranteed operating minimums. The sensitivity and text-rate contrast between A and B refers to these examples. HF sensitivity figures do not describe the FM radio path.
Why I built JSQ · Jerome Goddard II, W4IJG
The parts I loved.
The experience I wanted.
My goal for JSQ is a paradigm shift in amateur radio digital modes: separating the services we use from the modem or waveform that carries them. I hope JSQ will be the first of many projects to embrace this approach, giving operators the freedom to choose the link that suits the path while keeping the capabilities they rely on.
I was an avid user of FSQ, JS8, and AX.25 packet on APRS. I loved the freedom of keyboard-to-keyboard conversation in FSQ. Its commands also let us build an ad hoc network: relay a message, repeat my message, store and retrieve files, ask for heard lists, and check signal reports. We could check in, cooperate, and work out who could hear whom. JS8’s weak-signal reception, heartbeats, and signal checks were another part of what drew me in. JS8 also let me save a message on a station for later retrieval. That was a major motivation for JSQ’s mail custodian feature.
I liked the speed of APRS packets over AX.25 and the idea of exchanging files through a packet BBS. I wanted that usefulness without tying the workflow to a persistent connected-mode modem link.
But each system had its own modem and quirks. For the way I wanted to operate, the interfaces felt dated and centered on the modem. I wanted conversations, files, mail, and the network to be the starting point.
That became JSQ: bring those useful operating ideas together in a transport protocol above the individual modems. OpenJSQ is the application that puts that approach in front of the operator.
Where the name comes from
Conversation meets cooperation.
The name tells the story: J from JS8, and SQ from FSQ.
JS8 / JS8Call
Messages with somewhere to go.
Directed and stored messages inspired messaging and mail custody.
The shared design goalFSQ / FSQCall
A channel where stations cooperate.
Live conversation and cooperating stations inspired chat and station services.
The FSQ-derived actionsJS8’s weak-signal reception is an inspiration for the project. OpenJSQ does not use the JS8 waveform and is not over-the-air compatible with JS8Call. Peer compatibility · Performance evidence and limits
A clear boundary
Each layer has
one job.
- 01 Application
- Shows your chats, mail, files, and their progress. OpenJSQ is an application built on this model.
- 02 JSQ services
- Implement the common rules for messaging, mail custody, file recovery, groups, and network services.
- 03 Radio-link adapter
- Packages the same services for each radio link.
- 04 Modem or TNC
- Turns data into a radio signal and decodes received signals.
How radio links carry the services →Layer responsibilities →
Follow one useful task
Change the carrier.
Keep the file service.
Choose a modem below. The file service still tracks progress, recovers missing pieces, and verifies the complete file.
The shared JSQ service · unchanged
Reliable file transfer
- Track the file and its progress
- Recover missing pieces
- Reuse saved progress when the same file is offered again
- Check the complete file and report the result
The adapter and radio link
AX1200
AX1200 carries the file. Its speed and radio conditions determine how long the transfer takes.
AX1200 details →The adapter and radio link
JG25 Experimental
Experimental JG25 carries the file over FM. The same recovery and whole-file checks apply.
JG25 specification →The same file service works over each supported modem.
What the separation makes possible
Services and modems
can evolve independently.
Choose for the path.
Choose a supported modem for the radio path and keep the chat, mail, and file workflow you know.
Improve a service once.
An improvement to mail delivery or file recovery can serve all supported modems.
Add a link, not another stack.
A new modem can carry the existing services through an adapter, without rebuilding chat, mail, and file handling.
The published specifications let other applications implement compatible services.
The same workflow, different radio limits
The link still matters.
The radio path still determines speed, capacity, and delay. A small text file may be practical on a slow HF link while a larger file calls for a faster link. Both stations need the same on-air format and support for the requested service. Compare modeled file times →
Signals and peer compatibility →Delivery and custody definitions →
Explore the public service model.
Read the specifications, or see the services at work in OpenJSQ.