This interesting circuit of the American publication Electronics Handbook Volume XIII 1993 shows a crystal receiver where the detector can be any germanium diode (1N34 and 1N60), and is able to reject the signs of a stronger station interfering with others. This station is tuned in the upper variable, while the station you want to hear is tuned the lower variable. The handset should be high impedance or piezoelectric capsule in parallel with a resistor of 47k. The coils are formed by 100 turns of 28 AWG wire on a PVC pipe of 1 inch or broomstick. The variables are obtained from old valve radios. The antenna must be very long and the ground connection is important.
