This superheterodyne for medium wave has a crystal filter with about 6 kHz bandwith an a center frequency of 4,4 MHz, which is is also the IF. The mixer is based on a SA612. You don´t have to wind coils. This receiver needs only some fixed inductors.
I realized the receiver in the manhattan style circuit technique. A good grounding avoids unwanted oscillation and hum.
The receiver was built in the manhattan style technique.
The groundig is made by a piece of aluminium foil.
The lowpass filter in the frontend in order to supress the mirror frequency. R1 is the attenuator in order to avoid distortions. Cut off = 2 MHz.
The Lowpassfilter is designed with ADDE-Filterdesign.
The filter circuit in manhattan style.
The measured filter curve.
The mixer and LO.
The IF crystal filter.
Frequency curve of the IF filter realized by 3 crystals.
IF-amplifier and AM-demodulation.
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AF-preamplification with automatic gain control for the AF.
AF-Amplifier.
5 Volts and 12 Volts PSU.
The performance of the receiver:
Bandscan on mediumwave on a novemberevening 2013. The antenna is 30 m long wire.