Modulation in the Beacon
Edit on GitHubHow the SX1262 produces Morse: FSK carrier keying, the RadioLib calls and receiver behaviour
Modulation in the Beacon
Overview
A Morse beacon is just a carrier that turns on and off. This page explains exactly how the SX1262 does that with RadioLib, since the SX1262 has no OOK mode.
The Keying Mechanism
radio.transmitDirect(); // carrier ON (Morse element begins)
// ... hold for dot or dash duration ...
radio.standby(); // carrier OFF (element ends)transmitDirect() streams a raw FSK carrier; standby() silences it. Alternating between them produces clean on/off keying - CW.
What a Receiver Sees
| Receiver type | Result |
|---|---|
| AM demodulator | Audible Morse |
| WFM demodulator | Little or nothing (no deviation) |
| SDR waterfall | Carrier blips appearing/disappearing |
Frequency Stability
The E22 module’s TCXO keeps the carrier within +-1 ppm, so the frequency does not drift during a long payload. A plain crystal module would drift noticeably.
Why Not LoRa or FSK Packets
The design goal is that ANY receiver can hear the distress call. Raw CW is the lowest common denominator - no protocol, no synchronization, just Morse that a human or any AM radio can copy. LoRa or packet modes would need matching equipment on the rescue side.