how to relate the amount of turns for inductor of crystal radio to its performance?
They can be overlapping if you do not use the traditional slider on the coil to tune stations. The slider needs to be able to adjust the length of the coil to change frequency and if the coils are overlapping you would limit its range of tuning. In some crystal radio configurations a variable capacitor is used for selecting the frequency and these usually have overlapping windings. Most crystal radio enthusiasts agree that the sensitivity and selectivity is better with a single wound air core coil.
