Rap 'n Tap
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From: Gordon
Date: 8/21/00
Time: 1:33:32 PM
Remote Name: 24.93.21.238
I just completed designing and building a stator/rotor type variable inductor to be used as a variometer (stator and rotor in series)for BCB. The stator is 38 turns of #22 mag wire close wound on a 3" core which I calculate and measured to be about 130uH. The rotor is 50 turns of #26 mag wire close wound on a 1 7/8" core which I calculate and measured to be about 123uH. The inductance in series should be around 250uH,which I thought would be an ideal inductance for AM band. Is that right? I used a 365pf varicap paralleled with the coils and a diode on the antenna side of the coil/cap. All I got was shortwave! So I decided to try the coils as a variocoupler,separated coils and used the stator for the tuning coil and the rotor was connected to the antenna and ground.Using the same varicap and diode, I got AM stations from 800khz to above 1460khz, and a lot in between! Very selective and sensitive, compared to other sets I have built. I am pleased with the performance of this set, but my question is why? The tuning coil (stator) is only 130uH. I thought that BCB needed more inductance to perform??