Detecting RFI, revealing the causes of interference, locating unauthorized transmitters – all these are tasks performed by modern direction finding equipment. Spectrum analysis and time domain displays give much information about the type of signal, but they don’t reveal everything. They are limited to recording the amplitude versus frequency and / or versus time, and often lose information due to display compression. The full picture is only seen when the measured values are recorded without compression and separated into their real and imaginary components, usually referred to as the in phase and quadrature components, or I/Q for short.