Rap 'n Tap
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From: Larry P.
Date: 11/6/00
Time: 9:57:13 PM
Remote Name: 64.84.60.202
Nick,
I have to know a little bit more about the bar in order to tell you exactly how many turns to wind. But don't worry. You can just guess. You are bound to get something. Then you can adjust the turns or the capacitance (or a little of each) until you are tuning the whole band. It really is as simple as that.
Go to
http://photos.yahoo.com/bc/loose_coupler. Join Yahoo if you haven't already, so you can view the pictures. If you are just joining also check out http://clubs.yahoo.com/clubs/thecrystalsetradioclub . Lots of good discussion there too.
Look closely at the picture labeled "Slug tuned Close up". A picture is worth a thousand words. The main coil has about 40-50 turns. The antenna coil has about 25. Wrap some heavy paper around the rod snug but not too tight Tape it, then wind the coil on the paper. Use some double-sided masking tape around the paper. It holds the wires as you wrap and makes winding easier. If you want, you can use regular masking tape glued to the paper with the sticky side out. Don't wind so tight that you can't slide the coil on the bar. Put a fixed 250-350 pf cap across the 50 turn coil. Put the Diode Detector tap 25-50% from the ground side of the coil. Slide the bar in and out of the coil to tune the radio. Slide the antenna coil over the end of the bar to get some antenna coupling.
If you live in a weak signal area, or only have a short antenna, hook the antenna wire directly to the 50 turn coil. Try attaching it at several spots, like at the top, or at the point the diode is attached. If you make a lot of taps in the coil you can try then all. Notice how many there are on the radio in the picture. Tie the ground wire to the end of the coil that is opposite the antenna. Try all the possibilities. If you have a strong station nearby, you are likely to hear something as soon as you attach one wire or the other. Making a small radio takes a little more skill than a big one. If you get frustrated get the big wire and an oat box.
If you have a bunch of strong stations nearby, the Antenna coil on the end of the bar will help make the radio surprisingly selective. Experiment with how far you push this antenna coil onto the bar. Find out what works best.
This is just the beginning. Good luck. -Larry