Image-frequency FilterA low-noise RF amplifier stage ahead of the converter stage provides enough selectivity to reduce the image-frequency response by rejecting these unwanted signals and adds to the sensitivity of the receiver. The borders of the bandwidth of this amplifier are chosen to eliminate the image frequencies.Many older radar receivers do not use a low-noise pre-amplifier (RF stage) as the receiver front end; they simply send the echo signal directly to a crystal . This has any disadvantages. It is possible for these receivers to receive two different stations at the same point of the dial.