Inductive tuned ore radio ----- Simple Crystal Radio

First, the Q value of this spherical tube coil is measured with the Q table. Q The capacitor of the table is fixed at 55 pf, the result of the measurement is: Maximum inductor: 550 kHz q = 68 Intermediate Inductance: 745 kHz Q = 60 Minimum inductor: 2770 kHz q = 30 Q Table capacitors are fixed at 80 pf, and the results of the measurement are: Maximum inductor: 478 kHz q = 77 Intermediate Inductance: 995 kHz Q = 47 Minimum inductor: 2300 kHz Q = 15 It can be seen that the Q value of such a coil is not high, especially the internal and external two coils, and when the inductance is canceled, the Q value is lower. But use it to make ore machine tuning, you can easier the line without a variable capacitor. Below is a circuit diagram. The distribution capacitance of the antenna (generally dozens to more than 100 PF) and coils are parallel, and constitute inductive tuning circuits, and the fixed capacitor can also be saved. Be C1: 110 PF Air Ceramic insulation semi-adjustment capacitor, can choose a fixed capacitance replacement according to the actual situation of the antenna. C2: 250 PF fixed capacitor D: detection diode L1 - L4: variable inductive coil consisting of four hemispherical coils, maximum inductance 1188 & MH, minimum inductor 50 μH. Each coil is wrapped around 30 laps with a 22nd yarn. (The outer ring is 4.0 inches, L1 - left hemisphere, L2 - exterior hemisphere. Inner rings of 3.9 inches, L3 - left hemisphere, L4 - internal and white) S1: single knife 10 throw small rotary switches (only 4 S2: Single knife 10 throwing small rotary switch (only 3 files) Headphones: 4500Ω DCM headset The adjustment coil is fixed to a high stamped styrene drain pipe joint having a diameter of 4.5 inches, and the joint of such materials has a relatively low dielectric loss. Switches and wiring columns are distributed on both sides of the drain pipe joints. The half-tone capacitor is mounted back, and the capacitance can be adjusted by a small hole with a screwdriver, and the antenna is matched. Be Preliminary audition results: Connected to me, the sky, the ground, with the output line of the high-frequency signal generator around a few laps, constitute a small transportation capacitor input high frequency amplitude signal. S1 picks up the first gear (ie the antenna via the C1 connector) to check the resonance frequency of the variable reactive coil. When C1 is approximately 70 pf, the resonant frequency range is 530 - 2200 kHz, and the entire medium band can be covered. However, for several radios, adjustments S1 and S2 to the appropriate position, a larger sound can be obtained. Do not pick up the day, the ground, the antenna is only hanging next to the ore machine, and several radio can be received. Only ground wire, the sound is quite large, the selectivity is good. Only the antenna, adjust S1 and S2, selective good, four, five radio can be separated. The sound is relatively large. The day, ground, adjust C1, S1 and S2, selective is not ideal, medium wave low end and intermediate still. The high-end radio is basically not heard. The sound of the strong is very large.