FT8 via FM on 2 m: an easy way into digital modes
Proposal Run standard FT8 through ordinary FM radios on 2 m, so anyone with a handheld and a computer can make their first FT8 contacts. Suggested meeting frequency: 144.575 MHz.
This is an idea put up for discussion, not an established convention. The frequency is a suggestion and may change with feedback; nothing here has been agreed with a band plan authority or tested on the air yet.
Why
FT8 is the most approachable digital mode we have: structured messages, automatic sequencing, and contacts that complete and log themselves. On 2 m, though, it is run on SSB, and that is a barrier.
- An SSB-capable 2 m transceiver costs many times what an FM handheld does.
- Most newcomers, including Class N licensees who start on 2 m, own only an FM radio.
- So the people who would enjoy FT8 most as a first step cannot try it.
FT8 is only audio. Any FM radio can carry it, with the WSJT-X software everyone already uses. What is missing is an agreed place to meet.
A proposed meeting place
144.575 MHz lies in the 2 m all-mode segment (144.500 to 144.794 MHz), where the IARU Region 1 band plan allows FM. Neither the IARU nor the DARC plan assigns it a specific use. It sits just below the data centre of activity on 144.600 MHz and deliberately leaves that frequency free for the narrow modes that meet there.
- Attended operation only; this segment does not allow unmanned stations.
- Listen first. It is a shared frequency, not a reserved one, and local use may differ.
- Stay off 144.174 MHz, where FT8 is run on SSB. FM and SSB stations cannot decode each other, and FM there would disturb the SSB users.
Feedback and discussion welcome, feel free to mail me at dl1tj@darc.de.
What to expect
This is an entry point, not weak-signal work. FT8 on SSB decodes far below the noise; through an FM receiver most of that advantage is lost.
- Range: about what FM voice reaches on the same radios, perhaps a little more.
- One station per slot: FM receivers lock onto the strongest signal, so you will usually decode one station at a time, not a full waterfall. That is no deal breaker: unlike on HF, range on 2 m is local, so only a few stations share the frequency anyway.
- What you do get: the complete FT8 experience. Calling CQ, automatic exchanges, grid squares, logging, and spots on PSKReporter. And you gain experience: with the software, the timing and the operating habits, all of which carry over unchanged to FT8 on SSB and HF.
For range and DX, SSB remains the upgrade path. FT8 via FM is where you learn the mode with the radio you have.
Step by step
1Get the three things you need
- An FM radio for 2 m. A handheld is enough.
- A computer with WSJT-X ↗ installed (free; Windows, macOS, Linux).
- An audio cable with PTT between the two: a sound-card interface that fits your radio's speaker/microphone socket.
2Set up the radio
- Tune 144.575 MHz, FM, simplex (no repeater shift). Use narrow FM if the radio offers it.
- Open the squelch fully. A closed squelch hides weak stations from the decoder.
- Switch off battery save, CTCSS/DCS tones and any roger beep.
- Select low power. FT8 transmits for about 13 seconds at a time, every other slot, and handhelds get warm at full power.
- Use a vertical antenna, as on any FM simplex channel.
3Set the computer clock
FT8 works in fixed 15-second slots, so your clock must be right to within a second. Switch on automatic internet time in the operating system.
4Set up WSJT-X
- Settings > General: enter your callsign and grid locator.
- Settings > Radio: Rig “None”. PTT via the cable's serial port (RTS or DTR), or VOX if your cable has no PTT line.
- Settings > Audio: choose the cable's sound device for both input and output.
- Settings > Frequencies: add 144.575 MHz for FT8, then pick it in the main window, so your log shows the right frequency.
- Main window: mode FT8, transmit tone between 1000 and 2000 Hz on the waterfall.
5Check that you receive
With the squelch open you should see noise across the waterfall. Adjust the radio's volume until WSJT-X's level meter reads roughly 30 dB. If another station is on, its messages appear in the Band Activity list at the end of each slot.
6Set your transmit level
Start with the WSJT-X power slider low and raise it only until another station, or a second receiver of your own, decodes you. Too much drive makes the radio clip the tones, and then nobody decodes you.
7Make a contact
- Answer a CQ: double-click it in the Band Activity list. WSJT-X sends your call and locator, then the reports and 73, on its own.
- Call CQ yourself: click the CQ message, then Enable Tx. When someone answers, the exchange runs automatically.
- Log it: confirm the log window that opens when the contact is complete. It is an FT8 QSO on 2 m like any other, and you can upload it wherever you keep your log.
70 cm works the same way
Everything above applies on 70 cm as well: same radio settings, same WSJT-X setup. No frequency is suggested for 70 cm yet. The idea starts on 2 m, where more FM radios and more listeners are.
Status and sources
The audio-level and range statements above come from reasoning and a single simulation, not from measurements.
Open points:
- On-air test with two FM radios
- Check local use of 144.575 MHz before calling there
- Ask the DARC VHF/UHF/SHF Referat for its view on the frequency; the newest DARC 2 m plan found is from 08/2017
- Agree a frequency for 70 cm
- Confirm from the AFuV that Class N has no mode restriction that affects FT8
Band plans used: IARU Region 1 VHF Handbook 10.03 ↗, DARC 2 m band plan 08/2017 ↗.
Feedback and test reports welcome: dl1tj@darc.de.