The local oscillator excite a frequency for mixing with the incoming signal to get the intermediate frequency.Most radar receivers use megahertz intermediate frequency (IF) with a value between 30 and 75 megahertz. The IF is produced by mixing a local oscillator signal with the incoming signal. The local oscillator is, therefore, essential to efficient operation and must be both tunable and very stable. For example, if the local oscillator frequency is 3,000 megahertz, a frequency change of 0.1 percent will produce a frequency shift of 3 megahertz. This is equal to the bandwidth of most receivers and would greatly decrease receiver gain.