My current primary HF rig consists of an RS-HFIQ by HobbyPCB, used in conjunction with a Raspberry Pi 4 running Quisk, Fldigi, and WSJT-X. I’m calling the combination a “Pi-HFIQ”, and I’m hoping to put together a standardized hardware, software and documentation list to define it. The goal of the latter effort would be to help other hams replicate it successfully.
The RS-HFIQ, produced by HobbyPCB, is a QRP (low power) Software Defined Radio (SDR) based on the concept of quadrature demodulation (as opposed to direct sampling). Besides power and an antenna, it has three main external connections: RX I/Q out, TX I/Q in, and a USB control connection. What it requires in order to become a fully functional transceiver for the 80 thru 10 meter Amateur bands are a high quality stereo sound card and a computer. The sound card performs both analog-to-digital (A/D) and digital-to-analog (D/A) conversion for the transmit and receive in-phase and quadrature (I/Q) Intermediate Frequency (IF) signals (which are actually at audio frequencies).
I guess Quisk is technically the SDR… the RS-HFIQ is really the IF, since it doesn’t actually do any of its radio functions in software.