FAQ

FAQ

Short answers to the questions people ask first.

General

What is OnAir?

A free, open-source application for macOS, Windows and Linux that turns a software-defined radio (SDR) into a receiver and decoder: digital TV (DVB-T2, DVB-T, ATSC, ISDB-T, DTMB, DVB-S/S2, DVB-C), radio (DAB+, DRM, HD Radio, FM with RDS), aircraft and ships, satellites, two-way radio, pagers, amateur digital modes, IoT and much more. It shows the spectrum, waterfall and constellations so you can see what the receiver is doing. The mode list has every entry.

Is it free?

Yes: GPL-3.0-or-later, no account and no subscription. If it is useful you can support it on Ko-fi.

Which radios work?

The HackRF One and Pro natively; BladeRF, LimeSDR, USRP, PlutoSDR, Airspy, SDRplay, RTL-SDR, Airspy HF+, Fobos and RX888 directly; network radios; anything with a SoapySDR module. See Supported radios.

Do I need a radio to try it?

No. Press Tour, or choose the synthetic source: most modes include a built-in test signal. You can also open recordings from the sample library.

Which operating systems?

macOS 15 or later (Apple silicon and Intel), Windows 10 / 11 64-bit, Linux x86-64 and arm64. Android 9 and later is covered on the Android page.

Why is my radio not found on Windows?

Install the WinUSB driver with Zadig. See Troubleshooting.

Signals and law

Can OnAir decrypt encrypted channels or calls?

No. Encrypted TV services cannot be decoded, and encrypted radio calls (DMR, P25, TETRA and others) are only reported as encrypted. Nothing is decrypted.

Is it legal?

Receiving broadcasts is legal in most places, but laws differ, especially for private two-way radio, pagers and some aviation or maritime traffic. OnAir is built to receive; what you may do is up to you. See Legal.

Which modes have been tested on real signals?

Every mode page says what the mode was checked with. Where a mode has only been checked on generated signals, the page says exactly that, and recordings of real signals are welcome: upload them to the sample library or send them on Discord.

Why no sound on DMR, P25 or D-STAR?

Those use patented voice codecs that OnAir does not ship; you provide the library. See Voice codecs.

Does OnAir transmit?

OnAir is a receiver first. From 0.2.6 it also has a separate transmit view for licensed users; see the notes on the Transmit page.

Using it

How do I improve a weak signal?

Antenna height and a clear view toward the transmitter matter more than anything else. Use Auto-tune or Optimise gain and watch the quality score and the echo detector.

Can I watch TV on another device?

Yes: the built-in network tuner streams channels to VLC, phones, Plex or Jellyfin, as a plain stream or HLS. On a Mac you can cast to AirPlay. See the DVB-T2 tutorial.

Can I use two radios at once?

Yes, up to four receivers: Use two receivers.

Does OnAir work with an RTL-SDR for TV?

No: an RTL-SDR is too slow for TV channels. It works for DAB, FM and narrow modes.

What languages does it speak?

English, German, French, Spanish, Chinese and Lithuanian, with Portuguese (Brazil) and Hungarian added in 0.2.6 (View > Language).

Is there a command line or an API?

Yes: onair-cli and dect2scan and a remote-control HTTP / WebSocket API that is off by default.

Where do I start?

Getting started, then the Guided tour and the Tutorials.

How do I keep my favourite frequencies?

With the Memory panel (Ctrl+M), which stores the mode and settings too, and the Frequency database (Ctrl+Shift+F) for well-known frequencies. Both import and export CSV and JSON.

How do I find what is active in a band?

Use the Fast sweep scanner (View > Sweep scanner) and tune to a signal from its list.

My country's TV channels are wrong or missing.

Pick the country in the Scan tab (Band plan), or import your own plan: Band plans.

Can I record what I hear?

Yes: Record audio (WAV, FLAC or MP3) with an optional squelch-style gate (gating), and Record IQ for the raw signal.

Can I remove background noise from voice?

The neural noise remover in the General receiver and Airband, for NFM, WFM and AM speech only.

Can I use a radio on another computer?

Yes: rtl_tcp, SoapyRemote, SpyServer, SDR++ server, a PlutoSDR by IP and the SDRplay nRSP-ST through SDRconnect. See Network radios.

Does OnAir support up-converters and LNBs?

Yes: Ham It Up, Ham It Down, SpyVerter, QO-100 and Ku LNBs and custom converters. See converters.

Can I set my computer clock from GPS or a time station?

Yes, only when you press Sync now; see Clock sources.

Is there a touch layout?

Yes: Touch interface.

The picture or fax from the last pass is still there.

Results are kept until you clear them; see Clearing pictures.

Privacy and updates

What does OnAir send over the internet?

Almost nothing by default: an update check to GitHub. The map upload, PSK Reporter and similar are opt-in. See Privacy.

Can I turn off the update check?

Yes: the version button at the top right has the setting, as well as automatic install and pre-releases.

What is shared with the public map?

Only if you agree: decoded positions, never your location. See Map sharing and Privacy.

GitHub is blocked where I live. How do I update?

Use the update mirror: Update mirror.

Helping

How can I help?

Send recordings (especially for modes with little real-world testing), bug reports with an IQ recording, and pull requests; or tip on Ko-fi. See Contributing.

Problems?

See Troubleshooting for drivers, gain, crackling audio, high CPU, dropped samples, Gatekeeper and antivirus warnings, and how to send a bug report.

Android says the app cannot be installed over 0.2.6.

The 0.2.7 APK is signed with a new permanent key, so Android will not install it over 0.2.6. Uninstall 0.2.6 first, then install 0.2.7. Later updates install normally. See Android.

Can I use a KiwiSDR?

Yes, since 0.2.7: Add network radio... > KiwiSDR. It gives 12 kHz of HF spectrum around the tuned frequency, enough for narrowband modes such as FT8, WSPR, RTTY, CW and the general receiver, not for wide modes. See KiwiSDR.

Can I add my own decoder or run OnAir without a screen?

Yes, both are new in 0.2.7: the Plugin SDK adds a mode or action as a plugin file without rebuilding, and onair-server runs OnAir without a window, controlled from a browser.

Can OnAir alert me when a plane, ship or word is heard?

Yes: Watchlists (View > Watchlists) with desktop, sound, ntfy, Telegram and webhook alerts. The Message database keeps what was decoded and can search it.