Scottina's RTL-SDR screen turns an RTL2832U dongle into a five-second "what's transmitting nearby?" check: sweep a band for energy, decode real ISM packets and name the device, or grab a raw IQ capture for offline work. The RTL-SDR is receive-only — there is no replay or transmit path anywhere on this screen.
The RTL-SDR tile appears on Home only while the dongle is plugged in (and
disappears when you pull it), like the other device tiles. It needs the
rtl-sdr tools (rtl_power, rtl_433, rtl_sdr) installed.
Tap the RTL-SDR tile. Top to bottom:
| Control | What it does |
|---|---|
| ‹ band › | Cycle the preset band (see table below). |
| "likely:" hint | A per-band knowledge note — what typically lives here and how to go deeper. |
| Results area | The spectrum bar-graph (Scan) or the decoded-device list (Identify). |
| Status line | Current phase / peak frequency / decode count. |
| Scan | rtl_power sweep of the band → spectrum + a marked peak. |
| Identify | rtl_433 listens at the band's ISM centre (~6 s) and decodes packets, naming the device. Disabled on bands with no decoder. |
| Capture IQ | Records ~4 s of raw IQ at the peak (or the band centre) to a .cu8 file. |
| Band | Range | Identify? | Likely traffic |
|---|---|---|---|
| 433 ISM | 433–435 MHz | ✓ | Gate/car remotes, weather & temp sensors, TPMS, doorbells |
| 315 ISM | 314.5–315.7 MHz | ✓ | Car key fobs, garage/gate remotes, TPMS (North America) |
| 868 ISM | 868–870 MHz | ✓ | EU ISM: LoRa/Meshtastic (not decodable), meters, sensors |
| 915 ISM | 914–916 MHz | ✓ | US ISM: LoRa (not decodable), industrial sensors |
| FM bcast | 88–108 MHz | — | Broadcast FM (listen with rtl_fm) |
| Airband | 118–137 MHz | — | Aircraft AM voice |
| ADS-B | 1089–1091 MHz | — | Aircraft transponders @ 1090 MHz (use dump1090) |
"Identify" is only offered where rtl_433 has a decode centre — the other bands
show the hint instead and point you at the right dedicated tool.
- Spectrum (Scan): a bar per frequency slice, taller/greener = more energy. The white vertical line marks the peak; the status line names its frequency. A flat floor means nothing's transmitting in that band right now.
- Decoded list (Identify): one row per distinct device — the model name (e.g. a weather-station or TPMS type) plus a few decoded fields (id, temperature, battery, button code…). Duplicate transmissions are collapsed.
Capture IQ writes to:
/opt/kilodash/captures/iq_<kHz>_YYYYmmdd-HHMMSS.cu8
at 2.048 Msps for ~4 s. Pull it off with the Files screen or over
SSH and analyse it in GNU Radio / inspectrum / rtl_433 -r on a laptop. The
capture targets the last Scan's peak if you have one, otherwise the band's
decode centre.
"Is my 433 MHz sensor transmitting?" Band 433 ISM, tap Scan — a peak means something's radiating. Then tap Identify; if it's a supported protocol the model and its fields appear.
"What's on the air around here?" Step through the ISM bands with Scan; where you see energy, try Identify to name it.
"Grab a sample for later."
Scan to find the peak, then Capture IQ, and open the .cu8 on a laptop.
| Symptom | Fix |
|---|---|
| No RTL-SDR tile on Home | Dongle not detected — check lsusb for an RTL2832U (0bda:2838/2832). Re-seat it. |
| "No packet decoder for this band" | That band (FM/Airband/ADS-B) has no rtl_433 decoder — use the tool named in the hint. |
| "no known packets — see band note" | Nothing decodable was heard in the window. LoRa/Meshtastic on 868/915 is not decodable by rtl_433 by design. |
| Empty spectrum | Nothing transmitting, wrong band, or antenna not connected. |
| Captures fail | Confirm rtl_sdr is installed and the dongle isn't held by another process. |