Application of local oscillators in a receiver design requires care to ensure no spurious signals are radiated.
The oscillator must produce enough output power to effectively drive subsequent stages of circuitry, such as mixers or frequency multipliers.
Tuning to different frequencies requires a variable-frequency oscillator which leads to a compromise between stability and tunability.
With the advent of high-speed digital microelectronics, modern systems can use frequency synthesizers to obtain a stable tunable local oscillator, but care must still be taken to maintain adequate noise characteristics in the result.
The better WW II military communication receivers were engineered to suppress local oscillator emissions.