I recently tried to make a DIY foxhole radio. Althogh I made it according to the manual (140times coil rotated, ground(220V), blued razor blade, pencil core and antenna (just a steel stick about 1 meter), it doesn't work. And I'm guessing that the problem is the manual's AM RF(radio frequency)and my region's one don't match, so i've concluded that there's some realtionship between the RF and coil rotation times and i should know it. What's direct interaction between the coil rotation times and RF? And secondly, i learned that when you wish to receive radio signal, the LC circuit's resonance frequency should accord with the radio's one. But there's nothing seemingly similar to capacitor in the foxhole radio! I'm complicated, so i want to know how it works without the capacitor.
If the bandwidth of the LC tank is large enough it will catch all local radio stations that are strong enough. The design is probably meant to use stray capacitance. The problem is more likely in the demodulation. Try replacing the razor blade / pencil demodulator with a germanium signal diode or metal contact diode to troubleshoot. If the circuit works with the germanium diode then you can fiddle with the pencil / razor blade until you get diode functionality. If it doesn't work with the germanium diode then you need to check the rest of the circuit and make sure to have a good ground.