View Single Post
Old 04-17-2012, 01:16 AM
xee2 xee2 is offline
Silver Member
Join Date: Jan 2010
Posts: 580
Originally Posted by jake View Post
Any ideas?
Nice drawings.

When the two coils are close they "load" each other. This increases inductance of each coil, decreases Q of resonators, and provides more energy transfer between coils. In crystal radios increasing coupling between coils will provide more energy transfer but also decrease resonator Q. Usually minimum coupling is best since this produces highest resonator Q. If both coils are resonant at the same frequency then the Q of one coil will increase the effective Q of the other coil. This is how coupled resonator filters work. But the resonant frequency will change as the coils are brought closer together so they must be re-tuned after they are moved closer together.

I suggest you try coupling two parallel resonant circuits and tune to same frequency. This should give improved reception. Best if you can tune to frequency of near by radio station.

Or just make one parallel resonant circuit with large coil and weakly couple to it with a single loop or a small capacitor.

I would think your power detector would work better if the diode was in series with the amp meter. The circuit you have would work with a volt meter.

Please keep posting your results. I hope you will be able to light an LED from the RF signal.

Last edited by xee2; 04-17-2012 at 06:39 AM.
Reply With Quote