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In Reply to: RE: It's almost a crude crystal radio but the tuning portion is connected wrong.... posted by Steve O on January 15, 2017 at 21:38:42
Right you are about the diode attaching to the antenna. I missed that. Also, the place the diode is currently attached to should be grounded.
From my quick look at the LM386 data sheet, it does use low I/P impedance BJTs. Perhaps a simple JFET source follower between the diode and IC is needed. When I was a youngster, we used tapped tuning coils to connect to the diode and (ultimately) the BJT AF amp.
With a genuine long wire antenna and earth ground, a lightning arrestor is ESSENTIAL. That device can be made from a non-resistor spark plug.
Another tweak for the external antenna/earth ground setup is to connect them to a separate winding on the same form as the tuning coil. That winding has quite a fewer turns. Presto/chango step up transformer.
Follow Ups:
You can protect this with a GDT - which are about $4 in qty 1 from Mouser.
These guys are mini versions of the OB2 OA2 glow regulators.... They conduct around 90V or so, so your FET needs to have a gate breakdown voltage above that....
Another longwire protection device is a simple neon lamp....
-- Jim
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