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Weak-signal decoding
Digital processing can recover structured messages that may be hard to copy by ear. Results still depend on propagation, interference, audio quality and timing.
Digital DX · 11 metres
FT8 on 11 Metres
A practical DELTA TANGO guide to weak-signal digital radio, WSJT-CB software, station setup and the worldwide interest in making contacts when signals are difficult to hear by voice.
MODEFT8 digital signals
PROJECT REFERENCE27.265 MHz — verify local rules
START HEREReceive, decode, then configure carefully
01 · The basics
What is FT8?
FT8 is a computer-assisted digital radio mode designed for short, structured exchanges. Software decodes brief signals from the receiver's audio, displays decoded messages and helps operators complete contacts using timed transmissions.
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DX and propagation
11-metre conditions can change quickly. Digital activity can be an interesting way to observe changing paths, but no mode guarantees long-distance contacts.
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Radio plus computer
A compatible SSB radio, suitable audio connection, antenna and accurately synchronised computer clock form the usual station setup.
02 · Software desk
Which program should you try?
These applications are related, but they are not identical. Check the current release notes, supported operating system and callsign handling before choosing one for 11-metre use.
WSJT-CB
A community-developed WSJT-X fork aimed at CB-style identifiers and 11-metre digital operation. Use its own guide for installation, presets and callsign format.
WSJT-X
The established weak-signal digital-radio application and a useful reference for understanding FT8. Standard WSJT-X is not the same as the CB-specific fork.
JS8Call
Uses its own JS8 mode, based on FT8 technology, for more flexible messaging. It is not standard FT8 and cannot be assumed to interoperate with ordinary FT8 contacts.
JTDX
An alternative in the wider weak-signal digital-radio ecosystem. Do not assume it supports WSJT-CB-specific identifiers or presets; verify compatibility before recommending it for CB use.
03 · Beginner's checklist
Getting started, step by step
Start by receiving and decoding. The exact menu names and supported settings depend on your WSJT-CB release and radio model.
Install from the project source
Download WSJT-CB from its project page. Check the version and operating-system package, and avoid unofficial repackaged installers.
Connect your radio
Use an SSB-capable transceiver with a suitable USB or external audio interface. CAT control and a PTT interface may be needed for automated control.
Select audio and radio settings
Choose the correct receive and transmit devices. Follow the software guide for audio sample rate, sideband, radio control and transmit-level settings.
Synchronise the clock to UTC
FT8 uses timed cycles. Keep the computer clock accurately synchronised; the standard WSJT-X guidance calls for timing within about one second.
Listen and decode first
Select FT8 and the appropriate receive setup, then watch the waterfall and decoded-message window for several cycles. No decoded messages does not necessarily mean the setup is broken.
Check before transmitting
Verify the actual RF frequency, mode, equipment, audio level, PTT operation and local legal requirements. Do not transmit until each is confirmed.
04 · Reading the screen
What does a contact look like?
FT8 commonly exchanges short, structured messages in timed periods. These examples illustrate the idea; exact message formats and CB callsign support vary between software builds.
| Example message | What it means |
|---|---|
CQ 26AT716 | A station is calling for another station to respond. |
26AT716 30AT084 | A second station answers the CQ. |
30AT084 26AT716 -10 | A signal report is sent in this illustrative exchange. |
RR73 | Acknowledgement and sign-off message in common FT8 exchanges. |
73 | Best wishes / goodbye. |
CB-style identifiers may not fit standard FT8 callsign fields. WSJT-CB has project-specific handling; other decoders may not interpret every identifier in the same way.
05 · Check before transmitting
Frequency information and UK rules
Important: a published monitor frequency is not permission to transmit.
The WSJT-CB project has published 27.265 MHz as a reference frequency and 27.045 MHz as an alternative. Treat these as project/community references only. A frequency being inside the conventional CB band does not, by itself, establish that every digital mode, emission, radio or operating configuration is permitted in the UK.
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Confirm the current Ofcom conditions
Before transmitting in the UK, check Ofcom's current CB radio guidance and applicable technical conditions for permitted equipment, frequencies, power and emissions. If the status of FT8 on a proposed CB frequency is unclear, do not transmit until it has been confirmed through an authoritative source.
This page is an educational introduction, not legal advice. Community frequency listings and software presets do not override national regulations. Rules differ by country.
06 · Quick fixes
Common problems
Nothing decodes
Check the audio input device, selected mode, receive frequency, UTC clock, signal level and whether any decodable signals are present.
The waterfall moves but messages are blank
Confirm the correct input is selected, adjust audio levels, check the mode and listen for interference or excessively weak signals.
The radio will not transmit
Check the PTT/CAT configuration, interface wiring, radio transmit settings and the software's transmit controls. Do not test transmission on an unverified frequency.
Other stations decode the callsign differently
Check the identifier format and software compatibility. CB-specific callsigns may not be supported by standard decoders.
The transmitted signal looks too wide or distorted
Reduce audio drive, inspect the radio's ALC or transmit-level indicators and check that computer notification sounds are not entering the transmit audio.
Signals appear at an unexpected frequency
Check the radio dial frequency, sideband, audio offset and software preset. The RF frequency and the audio tone frequency are not the same thing.
07 · Primary references
Further reading
Use the original project and regulator documentation for installation details and operating decisions. Software features and regulatory conditions can change, so check the current pages before acting.
- WSJT-CB project page — project information and downloads.
- WSJT-CB guide — project-specific usage and configuration.
- WSJT-CB source repository — source code and project changes.
- WSJT-X full user guide — standard FT8 workflow, audio and radio setup.
- JS8Call — alternative digital messaging mode.
- Ofcom CB radio guidance — UK regulatory starting point.