OnAirDecode Multitone Paging with an SDR
Multitone Paging: tone and FFSK pagers for hospitals and sites, detector only (receive only).
- Group
- Pagers
- Start frequency
- 446.475 MHz
- In the mode list
- Pagers, tones and FFSK
What Multitone Paging is
Multitone Electronics is a UK maker of pagers used in hospitals and industrial sites. The air interface is narrowband FM with FFSK; the message layout is not public, so this mode is a detector.
Frequencies and settings
Multitone Electronics (UK) pagers, hospitals and industrial sites, 25 - 470 MHz, narrowband FM / FFSK. Detector only: the format is not public.
| Start frequency | 446.475 MHz |
|---|---|
| Tuning range of the mode table | 25 to 480 MHz |
| Sample rate asked | 2 Msps |
| Lowest working rate | 250 ksps |
| Channel width | 25 kHz |
OnAir takes any frequency you type; the numbers above are the mode's starting point and the range its table describes. In the app the shortcut label is Pagers, tones and FFSK.
What OnAir shows
Per transmission: carrier, deviation, steady tones and spectral lines of the audio; for FSK data the measured baud rate, the bit stream in hex and the 32-bit words that pass the POCSAG BCH(31,21) check, POCSAG sync flagged. Audio FFSK found in real recordings (tones f / 2f, 585 baud, the 0x605A frame word); the address and message fields are not worked out, so everything is unverified and no message text is shown; receive only, pager messages are private (see docs/multitone-research.md).
The mode's own tab has these views: Transmissions, FSK data, Tones. The other tabs (Overview, Receiver, Scan, History) are described on the main window page.
Limits and what it was checked with
The audio FFSK was found in real recordings, but the address and message fields are not worked out: everything is unverified and no message text is shown.
Which radio you need
Any radio that tunes this range works. An RTL-SDR covers roughly 24 MHz to 1.7 GHz, and every other radio in the radio guide reaches it too. Antenna height and a clear view of the transmitter matter most.
Receiving and the law
Questions about Multitone Paging
Can I decode Multitone Paging with an RTL-SDR?
Usually yes for narrowband signals, as an RTL-SDR tunes roughly 24 MHz to 1.7 GHz at up to about 2.4 Msps. Wide signals such as TV channels need a faster radio, and OnAir says next to the source what the selected radio can do.
Is it legal to receive Multitone Paging?
Pager messages can contain private information, and some countries restrict listening to them. Check the rules where you live before you use this mode.
Can I try Multitone Paging in OnAir without a radio?
Yes. Most modes include a built-in synthetic test signal, so you can open the screen and try the controls before you own a radio.