QRadioLink SDR Client Application for Linux

QRadioLink is a GNU/Linux multi-mode (analog and digital) SDR (Software Defined Radio) transceiver application that utilizes the network to achieve radio to VOIP bridging (radio over IP). It is built on GNU Radio and allows experimentation with different digital and analog radio signals using a Qt5 user interface.

Possible Uses

Experimentation, hobbies, and amateur radio applications.

Education (low-cost, low-complexity, low-reliability research platform for radio communication, digital voice and data radio applications, voice call routing).

Not for critical communications, industrial applications, and other applications requiring high data integrity.

Features

Send and receive UDP audio streams.

Interoperability with SVXlink via UDP audio.

Multicast radio to VOIP bridge (Radio-over-IP) connection between two or more endpoints operating in simplex or half-duplex mode. The VOIP bridge operates in a star topology where a central application (umurmur) acts as a voice packet router and provides logical channel separation.

Direct VOIP intercom (just connect to the VOIP server without a radio).

Radio forwarding via VOIP—forwarding analog or digital radio voice to VOIP connections and vice versa.

Transmit broadband audio streams over the internet using the Opus audio codec.

Configurable VOIP bitrate.

Support for TDMA MMDVM base station mode (DMR, System Fusion, D-Star, M17) using LimeSDR devices.

ETSI-compliant DMR base stations (repeaters) using LimeSDR series devices and MMDVM-SDR, supporting dual-slot TDMA.

Multi-channel/multi-carrier MMDVM system using LimeSDR devices. Supports up to 7 carriers in duplex mode at 200 kHz bandwidth. The number of channels can be configured between 2 to 7. Channel spacing can be configured to 12.5 or 25 kHz.

M17 digital voice modulator and demodulator.

Record local audio output in FLAC (Free Lossless Audio Codec) format.

Compatible with Mumble client applications.

Remote control over the network (requires telnet client or similar program, scriptable).

Remote control via private text messages in Mumble.

Headless operation (no graphical user interface), can be terminal used on embedded platforms like Raspberry Pi or similar headless boards.

Transceive analog FM, SSB, AM, digital voice, text information, digital video, and IP protocols.

Full-duplex DQPSK 250 kbit/s and 4FSK 100 kbit/s IP radio modem, configurable transmit/receive offsets.

Analog and digital mode repeaters—used only in full-duplex mode, same mode, or mixed mode repeaters (e.g., FM to Codec2 and vice versa; or FM to Opus and vice versa).

Connect radio nodes via VOIP and Mumble protocols—connecting a set of radio nodes through sharing the same logical Mumble channel. The advantages of using the Mumble VOIP protocol include: multicast full-duplex voice transmission, no call setup overhead after initial network connection, simple implementation, user-defined logical channels, free software, and open standards. This feature is still under development.

Full-duplex and simplex operation.

Quickly adjust repeater reverse shift using dedicated buttons.

Split frequency operation (transmitting on a frequency different from the receiving frequency, no shift restrictions, mainly used for repeater operation).

Store channels (store frequency, name, transmit shift, operating mode, squelch value, volume, transmit power, receive gain, transmit and receive CTCSS) and store channel scanning.

Mixed mode operation (receive one mode, transmit another mode).

Digital voice codecs: Codec2 700 bits/sec, Codec2 1400 bits/sec, Opus 9400 bits/sec.

Digital voice modem air bit rates from 1 kbit/s to 10 kbit/s.

FreeDV digital voice modulator and demodulator (currently supports only 1600, 700C, 700D, and 800XA modes).

Transmit broadband digital voice streams over the internet using the Opus audio codec.

Digital Modulation:M17 digital modes, FreeDV 1600, FreeDV 700C, FreeDV 700D, FreeDV 800XA, BPSK, DQPSK, 2FSK, 4FSK.

Analog Modulation:FM (12.5 kHz), narrow FM (6.25 kHz), SSB, AM, Wide FM (broadcast, receive only).

Simple low-resolution video mode (JPEG encoded), running at 10 frames per second at 300 kHz bandwidth, now playing sound at 9400 kbit per second using the Opus codec.

Analog modes (AM, FM, SSB) configurable filter width.

CTCSS encoder and decoder for analog FM.

VOX mode with configurable VOX volume.

Support for USB FTDI (FT232) relay control (for RF switches, power amplifiers, and filter control). Supports up to 8 relays on the board.

Automatic carrier tracking and Doppler effect correction. The system can track Doppler frequency shifts of up to 5-10 kHz, depending on the mode. It requires a CNR of at least 10-12 dB, with higher requirements for FSK modes than for PSK modes.

Supported SDR Hardware:Ettus USRP bus devices, RTL-SDR, ADALM-Pluto (PlutoSDR), LimeSDR-mini, LimeNET-Micro, BladeRF, and other devices supported by gr-osmosdr (HackRF, RedPitaya, and other untested devices).

Support for LimeRFE RF front-end. Only supports amateur radio bands. LimeRFE boards with cellular paths are not supported. The front-end’s automatic tuning is based on the IARU Region 1 band plan.

Note: QRadioLink uses code from the gr-cessb GNU radio out of tree module. Since some distributions do not package this module, the code is included in the application.

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