Regenerative Radios

appreciated.http://www.techlib.com/electronics/regen.html

Would A 180 uH or 470 uH choke work as the coil? If not I will have to wind my own coil.

Do you really want to receive the entire BC band at once? Notice that the designer put in a trap to keep BC band out.

appreciated.http://www.techlib.com/electronics/regen.html

I found another circuit, that uses a 2N3904, at

Can I leave the LM386 amplifier out, and could I use a 3.5 inch coil form with SWG21 wire? The schematic has two specs for the coil, which one is for AM? I'm not good with working with coils, I know how to wind them, that's about it.

The trap is a mod that can be used, if needed, when using the receiver on shorter wavelengths. It would not be present when the BCB is wanted.

Both are for the BCB, Use the one that matches the tuning capacitor you want to use.

The broadcast band would swamp a regen receiver. The selectivity or lack of would render that band useless for the receiver. I suspect that's why the trap was added.

Tom

appreciated.http://www.techlib.com/electronics/regen.html

at

What pins would I connect to on the LM386? I just found one of these in my junk box, and want to use it.

Dave,

I have wound many homemade coils that work in the AM range you have interest in. There is also a coil calculator. Check out what commonly available materials I use at this link.

Good luck,

• * * Christopher

Temecula CA.USA

First, you actually may get more out of the project by tuning shortwave frequencies. IN the broadcast band, you the regen won't actually mean that much on local stations, you may also find that the ease with which a regen can kick into oscillation will be annoying on the broadcast band that consists of AM signals, since the oscillation will beat against the carrier of the station and cause an annoying beat note.

On shortwave, you get new territory, and the gain of the regen will start being useful. Plus, you'll come into contact with signals that require the regen to go into oscillation, so you get to sample that.

On another matter, the thing about regen receivers is that they've often focused on simplicity. In the beginning, that reflected the cost of components, but then in more recent decades it's because there are better reception schemes, which are complicated, so the only reason to use regenerative receivers was for the simplicity.

Yet, modern components have made it so easy to make things better. In the days of tubes, nobody wanted to add extra tubes since the cost was there and it increased the size of the receiver. But semiconductors are outright cheap, and their size means you can have hundreds or more transistors in the space that one tube took up.

Charles Kitchin has done quite a bit of work on regen and superregen receivers, going back to the beginning (instead of cascading on what's been there recently), trying to distill the basic concept and seeing how to improve upon it. He's published quite a few different regen receivers (and some superregens) that are still relatively simple yet don't go for the fewest of components.

So he'd add a stage of amplification before the regen detector, not because amplification was needed, but because it isolated the detector from the antenna, so the antenna moving around had less affect on the regen's operation (in the old days, a single stage regen would pop into oscillation because the antenna waved in the wind). It complicates the electronics, though only relatively speaking, but it simplifies useage. He'd add voltage regulation, again to help stabilize the amount of regeneration so it didn't suddenly pop into oscillation. In the tube days, voltage regulation would require another big tube, in solid state times, it's a diode or three terminal regulator, nice and easy.

But most of his designs have also focused on being easy to build. So he uses things like 35mm plastic film boxes to wind the coils, though I suppose at this point those are getting scarce as film cameras disappear. In at least one design, he used a varactor for tuning, to sidestep the issue of getting a variable capacitor. He even had one that used a crystal for frequency selection, useless for most purposes but great when there was a code practice station on that frequency.

So you might do a search on "charles kitchin", at least some of his designs have appeared on the web.

Michael

Before somebody swears at you, have you considered browsing to your favourite search engine and entering 'LM386 datasheet'? It's free, it shows initiative, and you'll get a result FAR more quickly than waiting for somebody to do it for you.

I couldn't agree more. In fact, at the risk of sounding like a boring old fart (or a teacher), nowadays there seems to be little point in constructing any kind of simple radio other than for the purpose of discovering for one's self how the things work, how they're designed and put together, and what the design options are. Asking people in a Usenet group for elementary stuff like this just seems bonkers and counter-productive - if the desire is only to obtain a working radio with the least effort then the best solution is to visit a pound shop (in the UK; five and dime, etc. elsewhere).

But perhaps any blame should be shared by all the willing, helpful collaborators (including myself on occasion) who rise to the bait! Perhaps if every banal request was met by a standard 'go Google it' response every time the perpetrators would get the message and become bored of asking the obvious. The grey area would be those requests for which the responses sometimes turn up facts useful to others.

Chris

How about this thought?

You sketch out what you think you must do to make it work, scan it, and post it to a.b.s.e. Then ask for comments. You'll get much more out of it that way.