Magnetrons in radar transmitters are known to have a poor frequency stability. Since WW II the solution is known. In rada receiver, you have to use the AFC circuit which tunes the local oscillator to actual transmitter frequency.
You do not indicate receiver IF bandwidth which should be designed to match the transmitted spectrum and the AFC pull-in bandwidth.
The real bandwidth then determines receiver noise floor, noise figure and radar range.
Read Skolnik : Radar Technology, written in ~1960. All answers are there.