Sub-GHz Capture
How Echo captures signals, tunes to a target, and hunts for the right frequency.
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Every decode starts with a clean capture. Echo's radio is tuned for the busy 410-450 MHz band and can receive across a wider range for reception-only work.
The radio at a glance
- Tuned band
- 410-450 MHz, up to +10 dBm
- Wider reception
- 300-348 / 387-464 / 779-928 MHz (reduced sensitivity outside the tuned band)
- Default frequency
- 433.92 MHz
- Signal types
- OOK/ASK (most remotes) and FSK (many sensors)
Capturing a signal
For remotes, Echo records the raw on/off bursts a fob transmits, then analyses the timing. Pressing a remote several times lets Echo compare repeats and be confident it read the code correctly, one press can be enough, but repeats resolve ambiguity around noisy edges.
What you see in the app while a capture is running:
- A live view of the pulses as they arrive.
- A repeat count, how many times the same pattern was seen.
- The decoded result once Echo is confident, protocol name, or "unrecognized" if nothing matched.
Sensor traffic (TPMS, weather, alarm) is framed rather than raw pulses, Echo listens for a matching sensor packet and decodes it as soon as one arrives, there's nothing to "press" on the transmitter side, you just start listening and wait for the next transmission. See Sensor Decoders for what each sensor type reports.
Tuning to a target
Echo's default capture setting is a proven configuration that works for most remotes out of the box. When a target doesn't decode cleanly, the app exposes the underlying receive settings to adjust by hand:
- Modulation
- OOK/ASK (most fixed-code remotes) or FSK (sensors and some newer remotes)
- Receive bandwidth
- How wide a slice of spectrum the radio listens across, narrower rejects more noise, wider tolerates more frequency drift
- Data rate
- The expected signalling speed of the target
- AGC
- Automatic gain, high/normal/low, trades sensitivity to weak signals against resistance to a strong nearby signal swamping the receiver
- Frequency offset
- A fine nudge either side of the tuned frequency, see Autotune below
- Deviation
- FSK only, how far the signal swings from centre frequency
Autotune
Older remotes drift in frequency as their crystal ages, a fob that should be dead-on 433.92 MHz might actually be transmitting a little above or below it. Autotune sweeps the frequency offset up and down in small steps, retrying the capture at each step, and locks onto whichever offset actually decodes the target. Run it when a remote is close to the right frequency but won't quite decode.
The frequency hunter
When you don't know a target's frequency at all, the frequency hunter scans across a range you choose and reports signal strength at each step, live, in the app. The strongest point in the scan is almost always your target's channel. Once you've found it, switch to a normal capture centred there.
Reading a capture
A typical capture result in the app includes:
- Protocol
- The matched fixed-code family (see Fixed-Code Decoders) or the rolling-code make (see Rolling-Code Handling), or "unrecognized"
- Signal strength
- How strong the capture was, useful for judging range and interference
- Repeat count
- How many identical transmissions were seen, higher gives more confidence
- Decoded fields
- Protocol-specific, address/button for fixed-code, serial/button/counter for the rolling-code makes Echo reads in detail
From here you can save the capture to the signal library, replay it if it's a fixed-code signal, or just note what you found.