I've gotten a lot of suggestions for alternatives to the 1N34A diode as a detector in crystal radios. I have tested several, including power diodes like the 1N4007 (not worth showing) and the Schottkey diodes (on the oscilloscope it looks good, but is muffled compared to the 1N34A or D9K in actual use).

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1N34A
Forward voltage drop: 1V @ 5mA
Breakdown voltage: 65V @ 1mA
Reverse leakage current: 30µA @ 10V, 500µA @ 50V
Flat Junction capacitance
Lower leakage current
Absolute Maximum Ratings: (TA = +25C unless otherwise specified)
Peak Inverse Voltage, Repetitive (I R = 1mA), PIV 65V
Reverse Voltage DC, V R 20V
Peak Forward Surge Current, Non−Repetitive (t = 1sec), IFSM 0.5A
Peak Forward Surge Current, Repetitive, I FSR 200mA
Average Rectified Output Current, I O 50mA
Operating Junction Temperature, T J +75C
Storage Temperature Range, Tstg −55 to +75C

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D9K
Maximum reverse voltage U(BR) 30 V
Maximum forward current IF 60 mA
Maximum reverse current IR 60 uA
Forward voltage drop at the pnjunction U(F) 1 V
Frequency range, maximum Fd 100 kHz