Superhet Receiver on a 40-Meter Popcorn Version

This Superhet Receiver does not require AGC or RF control since it has satisfactory large signal handling capability as it operates with 4MHz intermediate frequency.

Only 6 bipolar transistors are used by this receiver along with an op-amp for sufficient volume into headphones. To terminate the diode ring mixers, one of two RF and AF diplexers are used. The RF amp is a 50Ohm feedback amp which has input impedance that properly terminates the band pass filter. To help provide a 50Ohm input impedance for the mixer, the receiver uses the -6dB attenuator pad following the amp. It also provides aid in preserving the signal to noise ratio of the receiver by reducing the stage gain. Reducing the PI attenuation to -3dB may affect the receiver dynamic range but it could add a little more sensitivity.

The ring mixer uses a 50Ohm diode and is followed by a RF diplexer. To protect the crystal filter from a catastrophically large signal to be present in the receiver’s front end, a 13dB limiter is formed by the four diodes. Unwanted ripples are prevented in the pass band by matching IF filter crystal frequency.

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