Back in 2016 Michael Ossmann, founder of Great Scott Gadgets and creator of the HackRF released schematics for 'Opera Cake', a rapid RF switching add on board for the HackRF. We also saw back in a January 2018 post how Opera Cake was capable of being used as the switching hardware for Pseudo-Doppler direction finding. Up until now Opera Cake has only been available as a schematic, for advanced hackers who could produce and build the board themselves.
Opera Cake is an antenna switching add-on board for HackRF One that is configured with command-line software either manually, or for automated port switching based on frequency or time. It has two primary ports, each connected to any of eight secondary ports, and is optimized for use as a pair of 1x4 switches or as a single 1x8 switch. Its recommended frequency range is 1 MHz to 4 GHz.
When HackRF One is used to transmit, Opera Cake can automatically route its output to the appropriate transmit antennas, as well as any external filters, amplifiers, etc. No changes are needed to the existing SDR software, but full control from the host is available.
Opera Cake also enhances the HackRF One’s use as a spectrum analyzer. Antenna switching works with the existing hackrf_sweep feature, which can sweep the whole tuning range in less than a second. Automatic switching mid-sweep enables the use of multiple antennas when sweeping a wide frequency range.