Receiver Compatibility
Edit on GitHubWhich radios and receivers hear the 433 MHz CW signal, and how to tune them
Receiver Compatibility
Overview
The beacon keys a continuous FSK carrier in Morse. Any receiver that can demodulate an on-off keyed carrier around 433 MHz will hear it - the CW signal is modulation-agnostic.
What Works
| Receiver | Mode | How to hear the beacon |
|---|---|---|
| Handheld scanner | AM or NFM | Tune to 433.500 MHz, listen for keying |
| Baofeng / ham HT with AM | AM mode (modded or supported) | Rare on Baofengs; most are FM only |
| Ham transceiver with SSB/CW | USB | CW tones appear as audible keying |
| RTL-SDR dongle + SDR# | Wideband FM or AM | Carrier blips visible on the waterfall |
| SDR with AM demodulation | AM | Best visual confirmation |
The FM Problem
Most cheap handhelds (Baofeng UV-5R and similar) are FM only. A pure CW carrier through an FM demodulator produces little or no audio, because the carrier is unmodulated in frequency.
| Receiver type | FM? | AM/CW capable? | Hears the beacon? |
|---|---|---|---|
| Baofeng UV-5R | yes | no | Usually poor |
| Baofeng with AM mod | yes | yes | Yes |
| Scanner (Uniden, etc.) | yes | yes (AM mode) | Yes |
| RTL-SDR | yes | yes (SDR) | Yes |
| Icom IC-705 / HF rig | yes | yes (SSB/CW) | Excellent |
Tip
The SDR is the cheapest guaranteed way to hear and SEE the beacon. An RTL-SDR dongle costs ~$15 and shows the carrier as a spike that appears and disappears with the Morse keying.
Tuning Steps
- Set the receiver to 433.500 MHz (or the beacon’s configured frequency).
- Select AM or WFM mode if available.
- If using SSB, tune a few kHz off and adjust the BFO pitch.
- Trigger a test transmission and watch for the carrier keying.
Verifying You Heard the Right Signal
The SOS pattern is unmistakable:
- Three short, three long, three short keying bursts.
- On an SDR waterfall it looks like three blips, a pause, three long blips, a pause, three blips.
- With GPS enabled the payload scrolls as plain Morse text a trained ear can copy.