BUILD THE RETRO REGEN RADIO

eburman
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Re: BUILD THE RETRO REGEN RADIO

Post by eburman » Wed Jan 06, 2016 3:31 pm

Thanks for your kind reply CeaSaR. I think that you must be looking at the cover photo for the article. It initially had me fooled too, but there is actually no vertical coil component. It's all part of a single spiderweb. There are two parts of the coil wound very close together. There is the outer antenna coil (L1) which is just a few circles of wire at the outer edge then there is an inner center tapped secondary coil (L2) which has many turns. There is no vertical component to this coil. It would actually be rather difficult to revise this coil once it has all been wound. But it sure does look really cool! I think I'll explore some articles I found on a really fantastic website- http://makearadio.com/coils/index.php. Using that information I might be able to revise the spiderweb coil for better performance. I could also try using Litz wire rather then enameled magnet wire. Is it worth the extra effort? The way the band is bunched up at the far nearly open end of the variable capacitor still has me thinking I've done something wrong. Maybe it'll work itself out if I redo the spiderweb coil. I used to think digital electronics was complex. Pfft! Old time analog radio is far more complicated and much more empirical!

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CeaSaR
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Re: BUILD THE RETRO REGEN RADIO

Post by CeaSaR » Fri Jan 08, 2016 1:20 pm

Well, seeing as I am using my phone to read most things these days, and the screen and mobile versions of the interwebs are small, I am sorry that I missed the actual construction part of the article.

Your main coil is a tapped coil. You can try moving your tap away from it's current position by scraping a small amount of the varnish off the wire and solder a small wire to that bare spot in order to attach the output of the coil. That way, you don't have to unwind anything, just a small scrape and solder job to adjust. Once you find the sweet spot, go over the unused bare spots with fingernail polish to re-seal the wire.

CeaSaR
Hey, what do I know?

eburman
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Re: BUILD THE RETRO REGEN RADIO

Post by eburman » Fri Jan 08, 2016 3:41 pm

Hey that's a great idea CeaSaR! Thanks for the tip.
Erik

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CeaSaR
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Re: BUILD THE RETRO REGEN RADIO

Post by CeaSaR » Sun Jan 10, 2016 7:07 pm

There is another type of tuning circuit where the coil has an exposed strip where a slider runs along the exposed edges of the coil to change the frequency. Think if it as having a tap at each turn of the coil. This is what prompted me to suggest the method I previously described to change the center tuning frequency of your spider coil. As a secondary thought, if you find a non-conductive way to hold your signal wire (from the tap), you won't need to do any soldering until you find the sweet spot.

CeaSaR
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eburman
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Re: BUILD THE RETRO REGEN RADIO

Post by eburman » Mon Jan 11, 2016 7:59 am

Yes, I was considering that option too. Just like old time crystal radios with the slider that runs across the coil. I'll probably wind up wrecking my beautifully wound spider coil but there's no better way to learn I suppose. I can always make another one. I also noticed that the tank circuit is affected by my antenna and ground system. The frequency band shifts around depending on which external antenna I use and whether or not an external ground is connected. One constant factor remains no matter how I tweak little things, I still can't tune in the upper end of the broadcast band so I guess I'll just have to try messing with the antenna coil center tap point.

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