GNU Radio example flowgraphs

116 flowgraphs covering analog and digital modulation, filtering, satellite and weather-image decoding, RDS, LoRa, OFDM, Wi-Fi and more. Every one opens and runs in the browser — no GNU Radio installation, no Python.

Analog

• AM ModulationInteractive amplitude modulation demo with time- and frequency-domain views
• FM LoopbackNoisy FM transmitter and quadrature-demodulator loopback with live tone and noise controls
• PySDR: Windowing, FFT Size, and the WaterfallCompanion to the Frequency Domain chapter of PySDR
• Low-Pass FilterCompare a two-tone signal before and after a 5 kHz low-pass FIR filter
• PySDR: AWGN in Time, Frequency, and DistributionCompanion to the Noise chapter of PySDR
• Noise Power MeasurementAdapted from GNU Radio's own example (gr-analog/examples/noise_power.grc).
• Showcasing the PLL Freq DetAdapted from GNU Radio's own example (gr-analog/examples/pll_freqdet_simple.grc).
• PySDR: Nyquist Sampling and AliasingCompanion to the Sampling chapter of PySDR

Audio

• Audio Frequency ShifterThis is a really simple audio frequency shifter
• Audio Tone GeneratorA tone played through the computer's speakers, with live frequency and volume controls
• FM Receiver from RecordingBroadcast FM receiver - a hosted 250 kHz IQ recording demodulated to audio and played through the speakers, with a live volume control
• FM Receiver from RTL SDRBroadcast FM receiver using RTL SDR
• Microphone SpectrumLive spectrum and waveform of whatever the computer's microphone hears
• SamSonic Musical KeyboardPlay synth notes and chords on the SamSonic musical keyboard

Blocks

• Block Interleaver ExampleAdapted from GNU Radio's own example (gr-blocks/examples/block_interleaver.grc).
• Demonstrating the effect of a Throttle blockAdapted from GNU Radio's own example (gr-blocks/examples/demonstrate_throttle.grc).
• Peak Detector DemoAdapted from GNU Radio's own example (gr-blocks/examples/peak_detector2.grc).
• Probe the rate of the Null SourceAdapted from GNU Radio's own example (gr-blocks/examples/probe_rate_message_debug.grc).
• Ridiculously High Flowgraph ComplexityA deliberately extreme but runnable signal-processing maze built to rack up bals—a whole lot of Bálints—across a chaotic mix of…
• Selector DemoAdapted from GNU Radio's own example (gr-blocks/examples/selector.grc).
• Simple Copy DemoAdapted from GNU Radio's own example (gr-blocks/examples/ctrlport/simple_copy.grc).
• Stream Demux demoAdapted from GNU Radio's own example (gr-blocks/examples/stream_demux_demo.grc).
• Stream Mux demoAdapted from GNU Radio's own example (gr-blocks/examples/stream_mux_demo.grc).
• Tag Propagation DemoAdapted from GNU Radio's own example (gr-blocks/examples/tags/test_tag_prop.grc).
• Variables and MessagesA flowgraph variable crossing into and out of the message domain.
• Vector Source With Tags DemoAdapted from GNU Radio's own example (gr-blocks/examples/vector_source_with_tags.grc).

Channel Models

• A Tone Through a Dynamic ChannelA pure tone through gr-channels' Dynamic Channel Model, a frequency-selective fading channel plus random-walk carrier and…
• PySDR: Flat vs Frequency-Selective FadingCompanion to the Multipath Fading chapter of PySDR
• Radio Impairments on a ToneA clean tone through gr-channels' Radio Impairments Model, every knob a live control.
• Spectrum Analyzer DemoAdapted from GNU Radio's own example (gr-channels/examples/demo_spec_an.grc).

Digital

• Burst Shaping and PDU ExtractionAdapted from GNU Radio's own example (gr-digital/examples/burst_shaper.grc).
• Burst Tagger DemoAdapted from GNU Radio's own example (gr-digital/examples/packet/burst_tagger.grc).
• Constellation Encoder and DecoderAdapted from GNU Radio's own example (gr-digital/examples/demod/constellation_encode_decode.grc).
• PySDR: BPSK vs QPSK vs 16-QAMCompanion to the Digital Modulation chapter of PySDR
• PySDR: 4-FSK and Frequency SpacingCompanion to the Digital Modulation chapter of PySDR
• GNU Radio.org Example8PSK with added noise, adjustable via range widget
• PSK Tx with Constellation8PSK with added noise, adjustable via range widget
• 16-QAM Modem LoopbackRandom bytes through QAM Mod, a noisy channel with a frequency offset, and QAM Demod.
• PySDR: BPSK Timing and Frequency SynchronizationCompanion to the Synchronization chapter of PySDR
• PSK Tx with Constellation8PSK with added noise, adjustable via range widget

Digital Television

• ATSC Transmitter DemoAdapted from GNU Radio's own example (gr-dtv/examples/file_atsc_tx.grc).

Embedded Python

• Python Block - Soft LimiterArbitrary Python DSP in the browser -- a soft limiter written as an Embedded Python Block, with its gain driven live by a slider

Filters

• PySDR: Low-Pass Filtering Out an InterfererCompanion to the Filters chapter of PySDR
• IChar DecimatorAdapted from GNU Radio's own example (gr-filter/examples/test_ichar_decim.grc).
• PySDR: RRC Pulse Shaping, Eye Diagram, and Sampling InstantCompanion to the Pulse Shaping chapter of PySDR
• Rational Resampler DemoAdapted from GNU Radio's own example (gr-filter/examples/resampler_demo.grc).
• PySDR: DC Spike and Offset TuningCompanion to the Sampling chapter of PySDR

GR World Challenges

• Challenge 09 blocks
• Challenge 1Add a Frequency Sink of your own, then look at a square wave in the frequency domain.
• Challenge 2Wire a slider to a block parameter, then tune the tone to 100.25 MHz while the flowgraph runs.
• Challenge 3Filter out an interferer, decimate what is left, and tell the display about the new sample rate.
• Challenge 4Multiply by a complex sine wave to slide a signal down to 0 Hz -- the move every SDR receiver makes.

gr-adsb

• ADS-B PlaybackReplays captured Mode S extended squitters through the ADS-B Decoder, no radio needed.
• ADS-B ReceiverReceives 1090 MHz ADS-B from an RTL-SDR and decodes the aircraft around you.
• ADS-B from a RecordingDecodes aircraft near Washington, DC from a hosted 1090 MHz ADS-B recording made at 49 dB gain, no radio needed.
• ADS-B from an SDRangel RecordingDecodes aircraft from a hosted 2.4 Msps SDRangel ADS-B recording, no radio needed.

gr-ais

• AIS ReceiverDecodes AIS position reports from ships in the hosted 250 kS/s SDRangel recording centered on 162 MHz.

gr-bbc

• BBC Concurrent CodesTwo messages OR'd into one codeword, both recovered.
• BBC Frequency Hop ControlA jam-resistant BBC control channel that commands a frequency hop.
• BBC LoopbackEncode a message with BBC and decode it straight back.
• BBC over OOK with a JammerBBC over OOK, recovered while a stronger jammer floods the channel with marks.
• BBC ZeroMQ Bridge (Browser Adaptation)Browser adaptation of the upstream ZeroMQ bridge.

gr-correctiq

• gr-correctiq DC Spike CorrectionA synthetic direct-conversion receiver signal with a controllable DC offset.

gr-droneid

• DJI DroneID frame detector — Mavic 3 Classic recordingsDetects a DroneID frame in either of two 40 MS/s DJI Mavic 3 Classic SigMF recordings by correlating the root-600 Zadoff-Chu preamble.
• DJI DroneID frame detector — Mini 2 recordingDetects DroneID frames in the public 50 MS/s DJI Mini 2 IQ artifact by correlating its root-600 Zadoff-Chu preamble.

gr-dvbs2

• DVB-S2 Transmitter and Receiver LoopbackBrowser-safe DVB-S2 short-frame QPSK transmitter and DVB-S2RX FEC receiver loopback

gr-fosphor

• Fosphor Spectrum and WaterfallInteractive real-time spectrum and waterfall display using gr-fosphor.

gr-ham

• CHU Time Signal DecoderDecodes the CHU shortwave time code from a 14670 kHz recording.
• PSK31 ReceiverDecodes a PSK31 QSO from a 40 m recording of 7071 kHz.
• PSK31 Varicode LoopbackEncodes a message to PSK31 varicode and decodes it straight back.

gr-hrpt

• HRPT NOAA Synthetic Image32 synthetic NOAA HRPT minor frames (32 AVHRR scan lines, carrying this repo's own logo on channel 2) that exercise the real…

gr-ieee802_11

• WiFi 802.11a ReceiverDecodes IEEE 802.11a frames from a 20 MS/s recording and prints each MAC header.

gr-ieee802_15_4

• IEEE 802.15.4 CSS Codeword LoopbackMaps bits to CSS codewords and decodes them by minimum distance with gr-ieee802-15-4.
• IEEE 802.15.4 QPSK Phase LoopbackMaps all four QPSK symbol pairs to phase and recovers their I/Q values with gr-ieee802-15-4.

gr-inspector

• gr-inspector Signal DetectorDetects a narrowband tone in complex Gaussian noise with gr-inspector.

gr-iridium

• Iridium PRBS15 Decoder TestDeterministic gr-iridium decoder sanity check using the upstream synthetic PRBS15 golden fixture.
• Iridium Recording ReceiverDetects and demodulates Iridium downlink bursts from the hosted 12 MS/s iridium_cf32 SigMF recording.

gr-lora_sdr

• LoRa Tx + Rx loopbackA complete LoRa link in one tab: gr-lora_sdr's transmitter feeds its receiver through a noisy channel, and each decoded payload is printed below.

gr-lte

• LTE PSS Synchronization from RecordingDetects the LTE primary synchronization signal in a real 1.92 MS/s RTL-SDR downlink recording.

gr-paint

• Paint a JPEG Into a WaterfallPaint a JPEG into a waterfall display.
• Paint an SVG Into a WaterfallPaint an SVG into a waterfall display.
• Paint a PNG Into a WaterfallPaint a PNG into a waterfall display.

gr-radar

• FSK radar simulatorAn FSK radar measuring one simulated target: two alternating tones bounce off something 200 m away closing at 20 m/s, and the…

gr-rds

• RDS ReceiverDecodes RDS from the 57 kHz subcarrier of a broadcast FM station.

gr-satellites

• gr-satellites AFSK demodulator (GOMX-1)AFSK demodulator component fed by the GOMX-1 recording
• AX.25 AFSK loopback using gr-satellitesAX.25 over AFSK, transmitted and received in one flowgraph
• AX.25 BPSK loopback using gr-satellitesAX.25 over BPSK, transmitted and received in one flowgraph
• gr-satellites AX.25 deframer (US01)AX.25 deframer component fed by the US01 recording
• gr-satellites AX100 deframer (1KUNS-PF, TW-1B)GOMspace AX100 deframer in both its modes: ASM+Golay on the 1KUNS-PF recording, Reed-Solomon on the TW-1B recording
• gr-satellites BPSK demodulator (LilacSat-1)BPSK demodulator component fed by the LilacSat-1 recording
• gr-satellites CCSDS deframer (BY70-1, TRISAT)CCSDS concatenated deframer on two recordings: BY70-1 as upstream has it, and TRISAT, which decodes here
• gr-satellites FSK demodulator (AAUSAT-4)FSK demodulator component fed by the AAUSAT-4 recording
• gr-satellites LilacSat-1 image downlinkLilacSat-1 image downlink: BPSK demodulator and LilacSat-1 deframer, printing the frames the image is carried in
• gr-satellites frame transport (TRISAT)Deframed satellite frames timestamped for transport, in place of the Python KISS TCP transport
• gr-satellites AAUSAT-4 decoder (assembled)What the all-in-one Satellite Decoder expands to for AAUSAT-4, assembled from primitives because the deframer is Python-only
• gr-satellites telemetry chain (GOMX-1)GOMX-1 telemetry: U482C frames, dissected by Print CSP Header in place of the Python telemetry parser
• gr-satellites U482C deframer (GOMX-1)GOMspace U482C deframer fed by the GOMX-1 recording

gr-tempest

• TEMPEST from a VGA RecordingRecovers the picture on a VGA monitor from a recording of the emissions its cable leaks (TEMPEST), using gr-tempest.

HackRF

• HackRF Receive ExampleReceive and display spectrum from a HackRF One over WebUSB.

JavaScript Blocks

• JavaScript Block - Amplifier ModelArbitrary DSP in JavaScript -- a power-amplifier model written as a JS Block, its distortion driven live by sliders, followed by…
• JavaScript Block - Tags and MessagesA JavaScript Block reads and rewrites stream tags while a shipped message-only JavaScript block adds metadata to a PDU.

OFDM

• OFDM Loopback and Bit Error CounterOFDM tx and rx with packet rate counter

Pdu

• PDU ToolboxEvery gr-pdu utility in one graph.
• Bursts with Take/Skip To PDUCuts a stream into PDUs of Take samples, dropping Skip samples between them, then turns the PDUs back into a stream to see the bursts.

PlutoSDR

• PlutoSDR Receive ExampleReceive and display spectrum from an ADALM-PLUTO using stock firmware.

QT GUI

• QT GUI Sink (all four plots)QT GUI Sink is the spectrum, waterfall, time and constellation plots in one tabbed widget rather than four blocks, which is the…
• QT GUI Control WidgetsEvery QT GUI control widget in one flowgraph.
• QT GUI Eye, Histogram and Time Raster SinksThree of gr-qtgui's sinks looking at one BPSK signal.
• Number Sink DemoAdapted from GNU Radio's own example (gr-qtgui/examples/Number_Sink.grc).
• QT GUI Vector and Matrix SinksThe two sinks that plot a whole vector at a time rather than a stream.

Recordings

• Recording Waterfall Test4 blocks

RTL-SDR

• RTL-SDR Simple Example7 blocks

Spectrum Analysis

• Signal Hound BB60C Spectrum AnalyzerNote the BB60C is in IQ streaming mode
• MMO-Style Spectrum AnalyzerThree independently fading signals across a simulated 1 MHz RF channel demonstrate the Spectrum Analyzer's MMO Mode with…
• Browser-Native Spectrum AnalyzerThree distinct signals across a simulated 1 MHz RF channel demonstrate automatic detection, per-signal peak measurement, center…

Usrp

• USRP B2xx Receive ExampleReceive and display spectrum from a USRP B2xx over WebUSB.