Posting Comment for "MCU Controlled Super-regeneration with Quartz Oscillators"

*Author Name
Email Address
Website URL

About Posting a Comment

Comments are moderated before they will appear on the website, this is a manual process and may take some time. Please be patient.

Author Name is a required field.

Email Address is optional, but without one I won't be able to contact you back. It is never shown or linked on the website. You can always just email me if you'd rather not post a public comment. I generally reply in-line with a comment rather than email you back, unless I want to discuss something in private or off topic. Please check back to see when I reply.

Website URL is optional, if supplied the Author Name will be hyperlinked to this URL.

You may use wikitext in the body, preview may be handy here. Don't worry if you can't figure them out, just give me a hint what you want linked to what and I'll do it during moderation. Wikitext is not BBcode!

Spammers: Please don't bother wasting your time scripting up posts to this form. Everything is moderated, your post will never be seen on the web even transiently, there is no way to even view it by its internal ID, it will never be indexed. I will simply delete your post in the moderation interface. If I'm your target audience you're really on the wrong track; I'll never click on a URL in your garbage. The post content is not emailed to me (and I don't use a Win32 mail client anyway), I view the posts in plain text in the moderation interface so no clever tricks of any kind will make anything you type be interpreted by anything other than me, a human. Just give up and go elsewhere please!

29th July 2011 18:47

Alan Yates wrote...


Yeah I should give that a try, must revisit some RF stuff soon!



29th July 2011 18:32

Bert wrote...

Perhaps you can use a ceramic filter instead of crystal for wider bandwidth?

25th February 2011 14:51

qrp-gaijin wrote...

If this crystal-controlled super-regen circuit can demodulate audio at HF, does that mean it can transmit voice (presumably FM) as well? Might make for a simple stable voice transceiver (like a walkie-talkie). With self-quenching it might be reduced to a single transistor.

I look forward to hearing about how the topology works for you.

7th February 2011 10:59

Alan Yates wrote...


Indeed a very interesting circuit!

I agree. I suspect the crystal is operating at its low-impedance series resonance to provide the emitter-collector feedback with the collector tank being the main resonator. This should sharpen the bandwidth over which is has significant power gain.

It is possible to allow the circuit to oscillate continuously I suppose, chopping the gain on and off and watching the rate of gain in oscillation amplitude when it is on. The high-Q crystal resonators seem to just keep ringing between high-frequency quench cycles in my experience, the gain drops enormously as raise regeneration frequency. If the oscillation isn't fully quenched the forcing signal you wish to measure is quite tiny compared to the remaining previous cycle's energy sloshing around in the resonator. I am unsure if you can force-quench a mechanical resonator like a crystal effectively? With LC resonators you can kill their Q and dump out the energy pretty quickly.

I'll have to build this circuit and see how it operates. Thanks for showing it to me.



7th February 2011 00:10

qrp-gaijin wrote...


You wrote, "It is often said that you can not super-regenerate crystal oscillators. In fact you can, but because of their high Q the quench frequencies needed are too low to carry high bandwidth signals like voice."

What do you think of this crystal-"controlled" super-regen, which apparently can demodulate audio at HF?

I say crystal-"controlled" with "controlled" in quotes, because the circuit has an LC tank which is I suspect the resonator, while the crystal serves I believe only to limit feedback energy to the crystal frequency. An interesting topology if I am understanding it properly.

16th August 2010 16:27

Alan Yates wrote...


The simple and robust nature of the Pierce oscillator is what makes this particular circuit practical. It is much harder to do the same with an LC oscillator. Simply replacing the crystal with a LC Pi network doesn't lend itself to easy replication.

I have found it easier to use two IO pins to control LC versions, typically keying the bias and detecting the signal envelope with different pins. You still need to discharge the capacitor in the envelope detector, so it must be an IO capable pin... Of course you can add extra circuitry to enable the use of just one control line or add a diode to discharge the cap via the keyline, etc.



14th August 2010 06:11

Glen Leinweber wrote...

Had tried a super-regen-to-MCU interface awhile back. Was a LC-based superregen. Instead of a diode amplitude detector, tried a more bare-bones approach where the RF was attached directly to the MCU I/O pin. When the RF grew high enough, it would trigger an interrupt on the peak of a cycle. Then the I/O was switched to "output" to quench the oscillator. Found that releasing the quench line (switching back to "input") introduced enough transient energy to excite the LC, reducing sensitivity greatly.

Seems your circuit overcomes this problem.

4th March 2010 03:54

gonio wrote...

Hi Alan,this is good work.

I use 11.0592 Mhz crystal in Rx & TX ckt.

On Rx side there is no change in rectified Vout,but few mV(1-3)change at collecor voltage even when both RX-TX very very close.

Plese can you help me to work this ckt.

23rd February 2010 11:32

David Rowe wrote...

Thinking about how this works a little more - as you say the receiver essentially samples the received energy just before oscillation starts.

Once oscillations start to build up the received signal no longer has much impact.

I think this is equivalent to sampling the baseband bit stream with a noise bandwidth equal to the receiver bandwidth.

For an ideal demod we would like to filter at approximately the bit rate, for example integrating over the bit period or using a matched filter. For example averaging over an entire bit would reduce the effect of an impulse.

So if your bit rate is 10Hz and bandwidth is 400 Hz, thats 40x (I think) more noise power than an ideal demod. This would have a large effect on the Bit Error Rate (BER) versus Rx power curve.

Using a bit rate at something approaching the receiver bandwidth and sampling once per bit might give better overall results (the extra bits could be used for error correction). This would require single sample/bit synchronization schemes.



21st February 2010 13:28

David Rowe wrote...

Fascinating work.

I am planning a HF messaging system (SMS/small email size messages) based on HF mesh networking. It's for people in the developing world so each terminal has to be cheap. It doesn't get much better than this sort of design!

I was wondering if these receivers would also be useful for PSK or FSK? Rather than amplitude detection the uC input could be used as a one bit A/D to sample the frequency and phase of any mixing products. DFTs actually work quite well with low amplitude resolution, and at these bandwidths can be implemented on a uC.

The way the RX signal builds up and is sampled reminds me a lot of "integrate and dump" coherent demodulation.

I of course assuming the super-regen process preserves frequency and phase at the RX.


David, VK5DGR