Great Scott Gadgets’ Opera Cake – Antenna Switching Add-On Board for HackRF One and other Software Defined Radios

Opera Cake is an antenna switching add-on board for HackRF One.

You can control Opera Cake for HackRF One manually with command-line software, hackrf_operacake, or you can configure HackRF One’s firmware to automatically switch Opera Cake ports based on frequency or time. Automated antenna switching and hackrf_operacake are both available in the latest HackRF One release. You can learn more about Opera Cake’s modes of operation in the HackRF documentation.

Its recommended frequency range is 1 MHz to 4 GHz.

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.

When set up as a pair of 1x4 switches you can use Opera Cake as a switched filter bank. To do this, connect port A1 to B1, A2 to B2, A3 to B3, and A4 to B4 through physical SMA filters and cables of your choosing. This setup allows you to change your transmit or receive to be through the filter of your choosing without having to reconnect hardware every time you would like to use a different filter.

As a 1x8 switch, Opera Cake can connect your HackRF to a variety of antennas at once, such as a long wire antenna for HF bands, a discone for VHF and UHF, a dipole for 2.4 GHz, and a dish for a satellite band. Once connected to your Opera Cake you can switch between all of your antennas in software instead of making physical hardware swaps.

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, or anything else in your RF chain. 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.