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RTL-SDR

Status

Status: Experimental, receive-only · Applies to: RTL-SDR

AetherSDR can use an RTL-SDR USB dongle as a receiver. Support is experimental and receive-only: one slice on one panadapter, demodulated on this computer. FlexRadio remains the supported target (see Supported Radios).

Where to go next​

Requirements​

The RTL-SDR backend is built only when the librtlsdr library is available, so whether your copy of AetherSDR has it depends on the package. If Connect by IP → Radio type: has no RTL-SDR (USB) entry, and no dongle ever appears in the radio list, your build does not include it. The Windows installer is built without it (#5800).

Building from source: the ENABLE_RTL option is on by default and takes effect when both librtlsdr and single-precision FFTW (fftw3f) are found. See Building from Source.

Setup​

  1. Plug in the dongle.
  2. Open File → Connect to Radio... → On This Network. Supported dongles on USB are listed with the network radios.
  3. Select the dongle and click Connect Selected Radio.

Using an RTL-SDR​

  • Modes: AM, SAM, FM, FM-N, WFM, USB, LSB, CW and CW-R.
  • Tuning range: 24 kHz to 1.766 GHz. Below 24 MHz the dongle uses direct sampling; HF reception on particular dongles (for example ones with an upconverter or the RTL-SDR Blog V4) has not been qualified.
  • Sample rates up to 3.0 MS/s; 2.4 MS/s is the default.
  • Browsing the capture: pan around the captured bandwidth and your slice keeps its frequency and settings. A slice that falls outside the usable capture is parked (silent) and resumes when it fits again.
  • Zoom uses a continuous 65,536-point FFT, which gives 36.6 Hz bins at 2.4 MS/s.
  • FM and FM-N have symmetric filters, 48 kHz audio and their own squelch. Squelch exists only in FM and FM-N; its level is a signal-level gate in dBFS per bin, not calibrated dBm.
  • Confirmed settings: a change is shown only after the dongle confirms it, so a refused setting never becomes a saved one.
  • Manual Black Level, waterfall NB Blank and FFT AVG work on the panadapter. See Panadapter Controls.
  • Tools → Radio Health... shows the dongle's status.

Only one receiver is available, even though the capture is wide.

Reference​

RTL Receiver settings​

Settings → Radio Setup... → RTL Receiver (shown while a dongle is connected) has a Receiver corrections group:

ControlUse
Frequency correction:Your dongle's crystal error in ppm (−1000 to +1000). Click Apply frequency correction to send it.
Suppress IQ DCRemoves the spike at the centre of the capture. Off by default.
Device serialThe serial number the dongle reports.

The page shows the values the dongle actually applied and whether they were saved. Corrections are saved per dongle serial number. A dongle that reports no serial keeps its corrections for the current session only.

What is remembered​

Frequency, mode, passband, sample rate and RF gain are saved per dongle, keyed by the serial number it reports. Dongles that report no serial share one family-wide entry, and so do two dongles that report the same serial.

Upgrading from an older version: saved RTL-SDR state used to be keyed by USB position. On the first connection after upgrading, a dongle whose only saved state is under the old key may start from defaults once. It then saves under its serial number (or the family-wide entry). The old entries are left in place but no longer read.

Not available on an RTL-SDR​

  • Transmit.
  • DAX, SmartLink or Multi-Flex.
  • More than one slice or panadapter.

Known issues​

  • An RTL-SDR Blog V4 on macOS shows only noise on the panadapter and in the audio, with no signals (#6016).
  • DX cluster, RBN, WSJT-X, POTA and manual spots are never drawn on the panadapter (#6039).

Troubleshooting​

No dongle in the list and no RTL-SDR (USB) radio type​

Your copy of AetherSDR was built without the RTL-SDR backend.

  1. Check Connect by IP → Radio type: for an RTL-SDR (USB) entry.
  2. If it is missing, use a build that includes the backend, or build from source with librtlsdr and fftw3f installed (see Building from Source).

The slice goes silent while you pan​

The slice has fallen outside the usable capture, so it is parked.

  1. Pan back until the slice is inside the capture again; it resumes on its own.

A spike sits at the centre of the capture​

This is the dongle's IQ DC offset.

  1. Open Settings → Radio Setup... → RTL Receiver.
  2. Tick Suppress IQ DC.

Stations appear off frequency​

The dongle's crystal is off.

  1. Open Settings → Radio Setup... → RTL Receiver.
  2. Enter the error in ppm in Frequency correction:.
  3. Click Apply frequency correction.

See also​