Will some one look at this PDF

On a sunny day (Sun, 26 Dec 2010 14:23:54 -0500) it happened Jamie wrote in :

It is a 'regenerative' receiver, and as such the catch is that it interferes with any station on the same frequency, as it oscillates. The high gain comes from the feedback. The oscillation goes on and of above the hearing range, some hundreds of kHz perhaps. Probably the roll of of the 741 opamp gets rid of that ;-) I would not use a 'better' opamp as he suggests :-)

Self-oscillating super-regen, to be exact.

John

And looks like a nasty emissionable unit on top of that.

Based on the fact that one pot on the receiver board is labeled "Regenerator" and on the comments in the document, it seems this circuit is a single-stage regenerative or design. So, yes, it's essentially a tweaked oscillator. You would crank up the gain (with the regen control) until the circuit is just on the threshold of wanting to start to break into self-oscillation, and the incoming RF from the transmitter would "push it over the edge" into oscillation.

A two- or three-transistor "super-regenerative" design would have more sensitivity and selectivity.

surely you mean "self-quenching super-regen"?

kevin

I understand how RG Osc's work how ever, I find it hard to believe that this one stage unit would have enough sensitivity to even work 1 foot of distant. I mean you would need a very strong TX signal, I would think? I don't even see previsions for an antenna, which would make it more plausible.

Jamie.

Oh well.

This used to be the most common design for Garage door opener and before that Radio Control and walkie-talkie receivers.

It is a super-regenerative receiver invented by Edwin Armstrong in the

In the super-regenerative receiver the feedback is increased until oscillation occurs at the intended receive frequency. Periodically (typically at 100KHz or so) the oscillation is stopped (quenched) and then allowed to build up again. Normally oscillators start-up from circuit noise or transients and take a time to build up: if there is a signal present at the oscillation frequency the oscillations will build up more quickly. The speed of the build-up affects the mean operating current of the circuit and so the presence of an input signal can be detected by filtering the supply current. The effective gain of the circuit can be 60-80dB in a single stage.

The quenching can be performed either by a separate low frequency oscillator or by judicious selection of bias components can be arranged to happen automatically, the circuit is then called self- quenching.

Normally the circuit is only sensitive to amplitude modulation but by slightly offsetting the tuning of the circuit it can demodulate FM using what is called slope demodulation.

These days there are many small modules available for remote control at 315MHz, 418MHz or 433MHz that use super-regenerative receivers. Their sensitivity is usually about -100dBm and only cost a few dollars.

kevin

In practice the regen is adjusted to the brink of bursting into oscillation, so a properly adjusted regen doesn't cause interference.

In any case its usually easy enough to put an untuned grounded gate antenna buffer in the front end to isolate the possibility of radiating.

The bad feature of any superregen is that it broadcasts strong interference. Hams really got pissed if you used one during Field Day.

ents

of

one: (928)428-4073

Most applications these days (such as the cheap remote control module and garage door openers) have an untuned RF amplifier in front of the super-regen stage to at least reduce the interference a bit.

kevin

"kevin93"

This used to be the most common design for Garage door opener and before that Radio Control and walkie-talkie receivers.

It is a super-regenerative receiver invented by Edwin Armstrong in the

In the super-regenerative receiver the feedback is increased until oscillation occurs at the intended receive frequency. Periodically (typically at 100KHz or so) the oscillation is stopped (quenched) and then allowed to build up again. Normally oscillators start-up from circuit noise or transients and take a time to build up: if there is a signal present at the oscillation frequency the oscillations will build up more quickly. The speed of the build-up affects the mean operating current of the circuit and so the presence of an input signal can be detected by filtering the supply current. The effective gain of the circuit can be 60-80dB in a single stage.

The quenching can be performed either by a separate low frequency oscillator or by judicious selection of bias components can be arranged to happen automatically, the circuit is then called self- quenching.

Normally the circuit is only sensitive to amplitude modulation but by slightly offsetting the tuning of the circuit it can demodulate FM using what is called slope demodulation.

These days there are many small modules available for remote control at 315MHz, 418MHz or 433MHz that use super-regenerative receivers. Their sensitivity is usually about -100dBm and only cost a few dollars.

My favourite shorter explanation is: " heap powerful magic ".

.... Phil

Trying to remember... wasn't there a _super_regenerative_ version that swept in and out of oscillation? ...Jim Thompson

In 1946, after WW II but before transistors, I built a super-regen RF receiver using two of the miniature vacuum tubes used in the proximity anti-aircraft shells. It fit in a case about the size of a match box, excluding the battery supply. It didn't have great audio fidelity, but could receive most of the broadcast FM transmitters then becoming common.

"VWWall"

Sounds a bit unlikely that such specialised tubes would be available to the public when they were still in full use.

The types you allude to were able to withstand an acceleration of over

..... Phil

Yup. You set up a second (lower-frequency) oscillation, which periodically "quenches" the main oscillation.

The gain of even a single-stage regenerative receiver can be impressive... the Wikipedia article says they range from gains in the thousands (valve) to around 100,000 (bipolar transistor), with gains of up to a million or so being possible in a super-regen design.

I'd guess that a "modern" high-end super-regen might be a three-transistor design: input buffer (to help keep the regenerator from leaking RF back out the antenna), main regenerative oscillator, and the super-regen "quenching" oscillator.

Interesting note in the Wikipedia article... it's apparently possible to operate a self-quenched super-regen circuit partway between the normal regenerative state and the super-regenerative state... and get some amount of FM detection as a result.

minor nit pick

"keep singing" might not be quite right. The battery did not start working until after the gun fired, so there was no singing until after that. Still, mighty impressive for a little bit of wire in a glass bubble.

"Jamie"

Should have at least heard of Super Regen receivers.

..... Phil

Nice to hear from you again Phillis..

Yes, I was aware of what it was, just couldn't see where the sensitivity was coming from to make it useful by itself with out some front end Amp. I still see no reference of an external antenna wire. One must assume this circuit was intended to run out in the open EM field. Not a good idea actually.

The last regen I saw had a band pass preamp on the front end and the OSC was in side a shield.

Don't get your knickers in a twist there boy!

Jamie

At the time, I was working in the tube department of a well known company.

Want one: