Open Signal — pictures over radio, done properly.
Open Signal sends colour pictures, photo files and text over HF and VHF radio in one self-contained executable for Windows and Linux — its own error-corrected digital mode plus classic SSTV across six families, with a logbook that fills itself. Receive for free, forever; full licences from £15 a year.
Four ways to send a picture over ham radio
Pick the trade-off you want — robustness, compatibility, or instant full quality. Nothing keys the radio until you press Transmit, and the staging card always shows exactly what goes on air and what it costs.
Photo
The actual JPEG travels over the air in error-corrected bursts and arrives byte-exact. 1–7 minutes by size — the EasyPal experience.
Hybrid
The full-quality picture goes via the internet and only a short link over RF — about five seconds of airtime. Needs internet at both ends.
Open Signal digital
A 320×240 colour picture in under a minute — forward-error-corrected, arriving pixel-exact instead of faded.
Classic SSTV
Six families — Martin, Scottie, Robot, Wraase, PD and MMSSTV's MP/MR — with automatic mode detection from the VIS header.
A whole picture station in one executable
Four ways to send a picture
The photo file byte-exact over the air, hybrid (a link over RF, full quality via the internet), Open Signal digital (its own error-corrected OFDM waveform), or classic SSTV — pick a mode chip and transmit.
Six SSTV families, auto-detected
Martin M1–M4, Scottie S1–S4 and DX, Robot colour and B/W, Wraase SC2, PD50–PD290 and MMSSTV's narrow MP/MR modes. The incoming VIS header tells Open Signal which mode is arriving and it just decodes it.
Hybrid cloud mode
One tick uploads the photo through the Open Signal picture service and sends only the URL — full quality in about five seconds of airtime, no storage keys to configure. Offline stations still see a readable link.
Text messaging with ARQ
Broadcast CQs with your grid square attached automatically, or use reliable ARQ delivery that retransmits until the other station acknowledges every block.
A logbook that fills itself
Every completed exchange is logged to SQLite with callsign, CAT frequency, mode and grid squares — then pushed live to Wavelog/Cloudlog, eQSL and a UDP ADIF broadcast.
Operator-grade receive view
A live 0–3 kHz waterfall and a pop-over that paints each picture in line by line with mode, resolution, time remaining and — for digital — live SNR.
Spotting & presence built in
PSK Reporter spots, DX-cluster announcements and an APRS-IS position beacon are all built in — no bridge programs, no virtual audio cables.
One self-contained executable
No FLDIGI, no Hamlib, no MMSSTV, no runtime installs. Copy OpenSignal.App.exe anywhere and run it — libraries and SQLite are compiled in (~35 MB).
Honest status — v0.22.3
The DSP, protocol, UI and integrations are extensively tested in simulation and against local test servers, and the app is now field-tested on the air, with live sessions on 144 MHz. One thing is not yet field-verified: interop with real MMSSTV — Open Signal implements the published SSTV specs and decodes its own signals under noise and clock error, but has not yet decoded an off-air MMSSTV recording.
- • The receive-only version is free, always — nobody gets left out of listening. The full version is licensed at £15 a year or £45 for life, and the installer arrives as a personal download link by email.
- • Open Signal photo-file mode is not wire-compatible with EasyPal — that would need a HamDRM/DRM modem (on the roadmap, not in the product).
- • Nothing is encrypted on the air; hybrid mode sends a cleartext URL.
Two ways in — one of them is free, forever
The receive-only version costs nothing and always will — listening is how this hobby starts, and nobody should be left out of it. When you want to transmit, a full licence is £15 a year or £45 for life.
Transmit, publish, everything
All four sending modes, the live network, galleries and profiles. Register with your callsign, verify by email code, and the invoice appears in your operator portal — pay by card when you're ready.
Receive everything, pay nothing
Decode every mode, watch the waterfall, browse what the network is sending — free forever, no trial, no catch. Ask below and the download link comes by email.
Open Signal — frequently asked questions
What is Open Signal?
Open Signal is a program for amateur radio on Windows and 64-bit Linux that sends colour pictures, photo files and text messages over HF and VHF. It combines its own error-corrected digital picture mode, classic SSTV across six families and byte-exact photo-file transfer in one self-contained executable, with a logbook that fills itself.
Is Open Signal free?
The receive-only version is free — permanently, for everyone. Listening is how the hobby starts, and nobody gets left out of it. The full version, with transmit and the live network, is licensed at £15 a year or £45 for life, paid by card through Stripe.
How do I get Open Signal?
Two ways: request the free RX version with the form on this page and the download link arrives by email, or register for a full licence (£15 a year or £45 lifetime) — verify your callsign with an emailed code and the invoice appears in your operator portal, payable by card. Updates arrive through the in-app banner either way.
Do I need extra software like FLDIGI, Hamlib or a virtual audio cable?
No. Open Signal is one self-contained executable with the DSP, SSTV codecs, database and rig control compiled in. You need a radio, a sound-card interface such as a Digirig or SignaLink, and your callsign.
Is Open Signal compatible with EasyPal?
Not on the air — Open Signal is not wire-compatible with EasyPal, which uses a DRM modem. Open Signal delivers the same experience (the real photo file, byte-exact) on its own more robust waveform, and it is actively maintained where EasyPal has had no updates since its author became a Silent Key in 2014.
Can Open Signal decode MMSSTV and other SSTV software?
Open Signal implements the published SSTV specifications for every supported mode and auto-detects the incoming mode from its VIS header. It decodes its own SSTV signals reliably under noise and clock error; interop with off-air MMSSTV recordings has not yet been field-verified.
What frequency do I use for SSTV pictures?
14.230 MHz upper sideband is the primary 20-metre SSTV calling frequency and a good place to start on HF. Out of the box Open Signal's dial frequency defaults to 144.550 MHz on 2 metres — set whatever your local activity uses, and with CAT connected it follows your VFO automatically.
Go deeper
Put a picture on the air today
Enter your callsign, pick a mode, and transmit — or explore every feature with no radio at all using the built-in demo station.