Regen Radio Ideas Needed

I found a circuit I really like, the only problem is it uses litz wire, but I can't see no reason why regular coil wire wouldn't work. It has an "RFC" I used to know what this was, I seem to have forgotten. I still remember that dse had one that was about 1 mH, will this work instead of the 2.5 mH? Also what type pot should I use, linear, or audio for the regen control?

Forgot the link:

Just done a bit of research on what RFC is, thanks to good ol' Wikipedia I now know it means radio frequency choke, and the one at Dick Smith is indeed 1 mH, wondering if that will do, if not how hard would it be to wind my own?

Hmmm, ya seem to be talkin' to yaself here Dave.

I'll bet you can find a 2.5mHy if look hard enough. If not, how about putting

Mike

"In view of such harmony in the cosmos which I, with my limited human mind, am able to recognize, there are yet people who say there is no God. But what really makes me angry is that they quote me for the support of such views." Albert Einstein (theoretical Physicist)

Yeah, I know :)

There should be a fair number of designs on the web, just google away. What frequencies are you trying to receive? What don't you like about the ones you've found? The most common layout in the past would probably be a detector followed by a stage of audio amplification, e.g. a 6SJ7 driving a 6C5 (both octals), or one section of a 6SL7 or 6SN7 driving the other section.

You shouldn't need litz wire - I believe that's only beneficial for frequencies below the BC band. Just use magnet wire.

Mike

The only band I'm interested in receiving is the AM band. Most of the circuits I've seen on the web usually have at least one part I can't seem to find. I can probably buy litz wire from Dave Schmarder (the webmaster of the site I linked to) if I really really need it.

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I highly doubt you need litz wire for the AM band. In fact, too high a Q at such relatively low frequencies will reduce your bandwidth to the point where you'll lose the few highs that an AM signal contains. So don't worry about it.

Make sure you can adjust the coupling between your antenna and the detector. You'll need very loose coupling to prevent any strong stations from pulling or otherwise overloading the detector.

Mike

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I know this is a stupid question, but what is coupling? Also, what size coil wire do I need?

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Coupling in this case is how the antenna signal is routed to the grid of the detector. For example, this design

As to wire size, probably #26 to #30 would do.

Mike

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Might work, but 1mH is kinda small. For AM band I might even go above

Mike

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Perhaps if I wire 2 chokes in series as someone previously mentioned? I might add more later.

The bigger problem is that the choke you're looking at is certainly designed for much lower frequencies, and may have a lot more capacitance than a choke intended for use at your frequencies. That capacitance will translate to lower impedance (bad thing) at your frequencies.

If you've got them already I'd say go ahead and try them. But if you're going to buy them, I'd say buy the correct type instead.

Mike

Hi Dave

I just built a superregen receiver. It is excellent. I can pick up FM and Air Traffic !!!

Let me know if your interested in which one i am talking about.

Shelton.

Of course a superregen is just an extension of the basic regen.

A regen is an amplifier with positive feedback, or an oscillator with controlled oscillation, depending on how you view it. The incoming signal goes through the amplifier, comes out stronger, and gets fed back to the input of the amplifier, where it gets amplified again, and so on. Howard Armstrong got a patent on the idea, and at the same time as inventing a receiver that was far better than already existed, in 1914, he showed how tubes could be used as oscillators (which was a big jump to, so those spark gap transmitters and alternator transmitters could disappear).

But, it's finicky. The point where the most gain and selectivity occurs is right on the verge of oscillation. That means a pretty unstable circuit, and every time you move your hand near the regen or the antenna sways in the wind, or the voltage varies, the regen can kick into oscillation, leaving terrible squealing in your ears. IN some cases you want that oscillation, to beat against an incoming signal, but you don't want it to happen unexpectedly.

The regen however provided lots of gain in only one stage, and while it had its limitations, so did the crystal radio (no active components) and the TRF receiver (multiple tuned gain stages on the signal frequency, also prone to oscillation).

Armstrong's next Big Invention was the superheterodyne receiver, the patent was issued in 1920. Far more complicated, it beat the incoming signal down to a fixed frequency where gain (and later selectivity) could easily be had, not just because it was at the time lower in frequency, but nothing needed adjusting in those gain stages after alignment, unlike all the other receivers that often needed adjustment every time you changed frequency.

Howard's regen patent was challenged, so he ended up in court. Just before the trial started, he hooked up his regen receiver to refamiliarize himself with the operation, and noticed an oddity that he had noticed when he'd originally played with the regen receiver. ANd that's when he discovered the notion of superregeneration, which he got a patent for in 1922.

The superregen is a regen receiver. The only addition is something to modulate the regen stage at an ultrasonic rate. It can be an external stage, that makes visualizing what happens so much easier. Or, far mroe common is the active stage of the regen detector is called upon to oscillate at an ultrasonic rate in addition to acting as the regen detector. This pulsing allows the regen detector to be on that verge of oscillation where the gain is the highest, but always pulling it back from there so it doesn't go into oscillation. It becomes a more "stable" circuit, requiring no regeneration control or any other control other than whatever is used to adjust frequency.

There was a time when you'd see regen receivers described and they were treated as both regen and superregen, since it was only a minor change, and done properly the same regen control that set things on the verge of oscillation or into oscillation if that was desired, could be turned up another notch and set the thing into oscillation at an ultrasonic frequency and hence it becomse a superregenerative detector.

So Armstrong created three receiver schemes that were and remain the three basic types of receivers over the years. Regens fell by the wayside decades back, though their simplicity makes them useful for project building. The superegen never really saw that much commercial broadcast use, but it saw plenty of use at the higher frequencies, and of course saw lots of use in cheap walkie talkies and garage door opener receivers over the years, I gather right up to the present.

The superhet had a slow start, it was useful but required all those tubes. But of course, it really won out, virtually any radio or tv set uses it. Only in recent years has any strong contender come along.

Michael

I'm interested in that as a future project, if you have a schematic please email it to snipped-for-privacy@googlemail.com. Thanks

I'm buying a one tube regen from Dave Schmarder. I don't get to build it, but I fell in love with it as soon as I saw it, I couldn't resist. It's using a #30 tube. Gotta love the shape of those things!