One of the great things about having a "miscellaneous" box in an otherwise well-ordered junk collection is that rummaging through that box will often send you off on fun and interesting radio adventures. I was rummaging yesterday and I came across the guts of the little AM radio that used to be mounted on my bicycle handle bars. I last mentioned this in 2011 :
I was just about to cannibalize this board. The IF transformers were almost certainly at 455 kc and I could use a few of those. But then I started thinking and Googling and trying to figure out the circuit. That all led me this the site that provided the diagram below:
Six transistors, four transformer cans, two audio transformers. Yea, that's pretty close to what I was seeing on my board. So of course I had to see if I could get it going. I hooked up a 9V battery. I connected the pot wiper connection directly to the connection at the top of where the pot had been (it had disintegrated). It works! It is inhaling nearby WFAX, Falls Church, Virginia.
You will notice that the transistors in the circuit above are PNP. I had assumed negative ground and had hooked the battery up accordingly. No smoke was released and the thing worked, so I guessed that I had assumed NPN correctly. Sure enough, perhaps aware of the PNP ancestry, the manufacturer had marked my board "BC123 NPN"!
The author of the book I linked to above dubbed this circuit the "All Japanese 6" -- an obvious allusion to the All American 5.
I see real potential in these AJ6s. A few mods to the front end and you could be shortwave listening, perhaps on 31 meters!
BTW: The space on my handlebars formerly occupied by that little AM radio is now taken up by a Bluetooth speaker that plays tunes streamed to my I-phone from Pandora as I make my way down the same old Washington and Old Dominion bike path. Progress.
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