Image Frequency

There are two frequencies, one above and one below the local oscillator, which if they enter the RF section, will heterodyne down into the IF and pass through to the detector. The undesired frequency is known as the image frequency and must be eliminated before it reaches the mixer.

 

In the standard AM receiver, the image frequency is higher than the local oscillator.

The image frequency can be higher or lower than the station of interest

The tunable circuits at the antenna and mixer inputs are designed to eliminate the image frequency.

 

 

Introduction to SystemVue