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/diy/ Do-It-Yourself

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Bananasplit 2015-01-05 22:02:47 No.751266

[Missing image file: ]

Any good (Lound and selective) crystal radio designs?


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Bananasplit 2015-01-05 22:12:55 No.751271
bump

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Anonymous 2015-01-05 22:15:10 No.751273
>>751266
'Loud' is going to be more a matter of how good your antenna is. An outdoor long-wire antenna, up as high as you can make it, is the best choice. A solid earth ground helps, too; a copper cold water pipe will probably do, but best is a ground rod pounded directly into the ground.

'Selective' is a matter of of the front-end of the receiver. In a passive design they used to use what they called a 'pre-tuner', which is (if I remember correctly) basically a duplicate of the LC circuit you use to tune the receiver now; you'd tune them both for best signal strength.

What are you using for a detector? Back in the day they'd use a bare chunk of galena and a very fine, stiff wire ('cats whisker'), and you'd pick a spot on the crystal that worked the best. These days germanium diodes aren't that easy to find, but you can still find 1N34's available online.

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Anonymous 2015-01-05 22:25:43 No.751280
>>751266
Just remembered something else you can experiment with.
I remember seeing designs where you forward bias the detector diode with a DC voltage. You'd use like a AA or AAA battery connected with something like 1M or 10M-ohm potentiometer, and also through a series resistor, on the anode of the detector. The idea here is to bias the diode closer to the point of conduction so that incoming signals will be detected easier, but not at so high a current as to 'drown out' the signal itself. Of course this now means that the receiver is no longer 'self-powered', but if the results are good then a single battery would last a long time due to very low current draw (way less than 1mA).

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Anonymous 2015-01-05 22:41:24 No.751291
Obligatory reading:
http://makearadio.com/crystal/index.php

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Anonymous 2015-01-05 22:42:10 No.751292
>>751271
How about you read the sticky and not act like a retard?

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Anonymous 2015-01-05 22:55:01 No.751299

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Bananasplit 2015-01-05 23:12:10 No.751305
>>751299
May I ask for the source of this pic?

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Anonymous 2015-01-06 02:25:00 No.751390
>>751266
>crystal radio
>loud and selective

I recommend building a regenerative radio receiver if you want better reception and loudness. It's only a little more complicated than a crystal radio.

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Anonymous 2015-01-06 03:10:38 No.751411
>>751390
>2N35 bipolar transistor
>'uuF' instead of 'pF'
Wow, that's a really old schematic, probably early 1960's?







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