OnAirPagers · Experimental
Decode FLEX with an SDR
OnAir receives FLEX. FLEX paging messages (1600, 3200 and 6400 bit/s) on a 25 kHz channel.
What FLEX is
FLEX is a faster pager protocol from Motorola (1600 to 6400 bit/s) used alongside POCSAG.
Frequencies and where it is used
Pagers, 1600-6400.
In OnAir the tuning shortcut is Pagers, 1600-6400; you can enter any frequency your radio reaches.
What OnAir shows for FLEX
FLEX paging messages (1600, 3200 and 6400 bit/s) on a 25 kHz channel.
This receiver is built from the published specification and checked end to end on simulated signals. It has had little or no testing on real transmissions yet, so reports and recordings on Discord are welcome.
Which radio you need
This is a shortwave mode, so the radio has to tune HF. An SDRplay, Airspy HF+ or an RTL-SDR in direct-sampling mode do that directly; with a HackRF an HF upconverter or a direct-sampling receiver is the usual route. A long wire or loop antenna matters more than the radio.
Questions about FLEX
Can I decode FLEX with an RTL-SDR?
An RTL-SDR can receive HF only in direct-sampling mode, which OnAir offers in its radio settings; results depend on the antenna. SDRplay and Airspy HF+ radios are better suited.
Is it legal to receive FLEX?
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 FLEX 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.
Try it without a radio
OnAir includes built-in synthetic test signals for most modes, so you can open this screen, see the layout and try the controls before you own a radio. The Tour button walks you through the app.