Local oscillator. In radio frequency systems, it is a signal generator built into a receiver or transmitter. Its output is fed into a mixer along with the incoming radio signal to produce an intermediate frequency (IF) that is much easier to filter and process.
Check the LO leakage at the mixer output, we're seeing way too much feedthrough on the spectrum analyzer.
A drifting LO is the most common cause of an older analog receiver failing to lock onto a signal.
Related terms
Mixer
A non-linear circuit that combines two different input frequencies to generate new output frequencies.
IF
A specific frequency to which a carrier wave is shifted as an intermediate step in signal processing.
Superheterodyne
Describing a receiver architecture that converts incoming radio frequencies to a fixed intermediate frequency for easier filtering and amplification.