Abstract: 1. A transmission frequency diversity radar system comprising an oscillator that is tunable over a frequency band to produce a signal for radar transmission, means for tuning said oscillator randomly on a random frequency basis, and means for frequency tracking the signal being transmitted including a variable frequency local oscillator, means to sweep the local oscillator over a range of frequencies within the pulse width time of the radar transmitted signal but after said transmission oscillator is tuned and modulator means responsive to the transmitted signal for holding said variable local oscillator on the proper tuning frequency.