a different receiver

[mstechca]

Its very interesting. I went to google, put in the search terms "short-circuit amplify" and I went across the following URL:

https://wehner.org/electro/short/

When I looked at it, he literally explained how it is possible to build a superregen receiver, and it works well in the FM radio band. Here's the circuit:

**broken link removed**

I think he is using a hartley oscillator in a common-emitter mode which to me is second best.

Is there some way I can modify this circuit so that it becomes a colpitts oscillator instead of a hartley oscillator without reducing gain and adding alot of components?

 

[David Bridgen]

What do you mean by "second best", and why do you think that?

 

[audioguru]

The author doesn't say that his super-regen radio works well, he says it gives "intelligible quality - despite the HISS".

Real FM radios have a very wide, undistorted audio bandwidth without any noticeable hiss.

 

[mstechca]

What do you mean by "second best", and why do you think that?

I learned that colpitts oscillators are better than hartley oscillators in terms of frequency stability. If I can somehow make a colpitts version of this circuit, that would be nice.

 

[JimB]

Colpits oscillators are good for stability because the large values of feedback capacitance can mask any variations in transistor junction capacitance (or valve inter electrode capacitance, if you want to go into history).

However, given the nature of a super-regenerative receiver, oscillator frequency stability is the least of your worries.
These things have such a wide passband, the stability of the basic oscillator is insignificant.

JimB

 

[audioguru]

Yeah Jim,
You tune a super-regen by simply going near it. :lol:

But I thought that besides not having an FM detector and relying on tuning to the side of an FM station to slope-detect it, its very high distortion was caused by it having a very narrow passband when oscillating. The Q of the tuned circuit must go through the roof when it is oscillating. Unlike other super-regen circuits that have a sensitivity control that is carefully adjusted to avoid oscillation, this circuit does, then stops by squegging, then starts and stops over and over. I wonder if its frequency sweeps a little as it gallops along.
It is amazing that this simple circuit does anything with its extremely low supply current. I might make one to see how easy it overloads from local stations since I have many.