Also known as: CubicSDR
CubicSDR is a free, open-source, cross-platform software-defined radio receiver known for its combined spectrum-and-waterfall view and for using SoapySDR as its hardware layer, which gives it wide device support out of the box.1 It runs on Windows, Linux, and macOS with the same interface, and lets a listener drag across the spectrum to tune and demodulate analog signals in real time.
How it works
CubicSDR opens its front end through SoapySDR, so any radio with a Soapy module — RTL-SDR, Airspy, HackRF, LimeSDR, SDRplay, and networked sources — works without app-specific drivers. The incoming IQ stream is processed with the liquid-dsp library: an FFT produces the spectrum and waterfall, and a digital down-converter plus demodulator extract the signal under the tuning cursor. Supported modes include WFM (with stereo), NFM, AM, SSB, and CW.
The interface, built with wxWidgets for portability, emphasizes the visual: a large, smoothly scrolling waterfall that the user drags across to retune, with the passband of the receive filter shown directly on the spectrum. Multiple demodulators can be placed at once so several signals stay visible, and audio can be routed per demodulator. CubicSDR can also act as a SoapySDR network client, receiving IQ from a remote server so the radio can sit at the antenna while the application runs elsewhere.
Relevance to SDR
CubicSDR occupies the same niche as Gqrx and SDR#: a friendly general-coverage receiver for browsing and listening to analog signals across the spectrum. Its selling points are true cross-platform parity and the SoapySDR foundation, which means the same build works with almost any front end and can talk to remote radios. Like other general receivers, its demodulators target analog modes; decoding digital-voice or trunked systems requires separate tools fed from its audio or IQ output.
GopherTrunk is an independent project unrelated to CubicSDR in code. Functionally they overlap only at the front end and the “see the signal” stage: GopherTrunk is a headless, pure-Go trunking scanner that consumes IQ and decodes digital protocols itself, whereas CubicSDR is a GUI receiver for manual tuning of analog modes. Because both can draw on the same SoapySDR-supported hardware (and CubicSDR can record IQ), CubicSDR is a handy companion for locating a control channel visually or producing capture files to replay through GopherTrunk offline.
Sources
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CubicSDR — the official project site and its source repository, documenting the SoapySDR device layer, the liquid-dsp core, the wxWidgets interface, and supported demodulation modes. ↩