FSQ is a Fast Simple QSO mode designed specifically for HF. It works well under NVIS and sunrise/sunset conditions on the lower bands, and also works well for short skip and grey-line on higher bands. It can also be used on VHF FM, and clearly has a much wider useful range of operating conditions that other more conventional digital modes. FSQ transmission is also well within the capability of micro-controller based devices for low-power propagation transmissions (MEPT and telemetry). The FSQ modulation, coding and FSQCall protocol are publicly disclosed and described, and the software is open source.

FSQ was developed by Con Wassilieff ZL2AFP with the assistance of Murray Greenman ZL1BPU. The first QSO took place between these two on 28th November 2014, and the first Alpha executable release was on 17th December 2014. The source code was released with the Beta version 0.23 on 3rd March 2015. The first US version release (V0.24 RC1 by Bob NW8L) was on 29th March 2015. The first full-package public release was by Bob NW8L on 29 April 2015. A version of fldigi with full FSQ support was released by Dave W1HKJ on 16 July 2015, and includes support for Linux and Mac platforms.

FSQ is intended for fixed frequency (channelized) operation, with dedicated calling frequencies. It isn't intended as a 'tune around to see what you can find' mode!