Comments for "AM Walkie-Talkie Experiments"

29th September 2014 06:54

Hue Miller wrote ...

I think you should use the hamband crystal and a decent antenna and see what kind of DX you can work. I wish i could find a few 3rd overtone crystals for 15M or for around 29 MHz !

In the 1960s, i think, Popular Electronics in its "Solid State" column showed a single tunnel diode 'voice broadcaster' for VHF - text said by simply adjusting the bias pot, it became a superregen receiver. There's your minimal transceiver!


26th March 2010 21:29

Alan Yates wrote...


Some context would help, is it for HF or VHF?

The core (if any), diameter and pitch are unknown, but 500 um wire and 9 turns suggests high HF or low VHF, probably with a diameter in the region of 5-10 mm.

You can generally guess the inductance required if it isn't specified from the capacitance in the circuit and the frequency of operation.



26th March 2010 13:18

HP wrote ...

Do you have any idea to make an inductor with such information : 9 turns,0,5mm diam emailed wire winded on empty oscillator stand ? Any idea? ^^

23rd September 2008 13:53

Anthony Sotillet wrote ...

Hi Alam..! Nice work.! Do you have any circuit to receive CB band? I'm some experiment with regen receivers and I don't get anything..!

17th September 2008 17:21

MedardRieder wrote ...

Hi Alan,

great article. Will you post the schematics?


7th September 2008 17:55

Chris McMahon wrote ...

Thanks! I suspected it wouldn't be that easy, I was hoping for an easily reproducible circuit where I could put multiple tx/rx pairs close to each other, but I guess that doesn't really matter if I only want to go a few feet. Heh, I'll have to find a good book or website about the theoretical stuff so I can figure out what I'm doing.

Thanks for the quick reply,


7th September 2008 00:47

Alan Yates wrote...

OK, I'll post the circuit diagrams tomorrow, you aren't the first people to ask for them.

Unfortunately the high Q of a crystal is impractical in a super-regenerative receiver. The quench frequency would be too low to achieve much bandwidth, probably only a few Hertz. The quench frequency could be lowered in a normal super-regen to achieve better selectivity, but the available bandwidth drops. The selectivity is four times the quench frequency minimum, and the usable channel bandwidth is one half the quench frequency maximum (Nyquist–Shannon limit).

6th September 2008 17:09

Chris McMahon wrote ...

Wow, those are really small.

Could you please post the schematics if you still have them? I'm looking for a small tranciver for micro controller projects. Also, do you know if it is possible for a (super)-regenerative receiver to be crystal controlled for closer spacing?

Thanks, Chris

10th May 2008 19:26

Alan Yates wrote...


Indeed, I've had similar thoughts.

Bob Culter N7FKI's QSK-1 (single-2N7000 based CW transceiver) is similar, but it doesn't change the bias which limits its output power a little.

Many of the old three transistor toy walkie talkies take a similar approach, but use lots of switching. One thing I was thinking about trying is to use the emitter follower modulation transistor to couple out the AF signal. That probably means putting a fairly large resistor in its collector, and that would require a high supply voltage. That resistance might be a AF receiver.



10th May 2008 09:10

David Moran wrote ...

Hello again!

I've been toying in my notes for a single transistor regen receiver that will transmit as well, push to talk pushes bias into full oscillation, releasing it lowers bias to regen levels, or sound power from the mic could reset the bias?

25th March 2008 17:27

Alan Yates wrote...


Thanks mate!

Yeah the camera doesn't like the fluorescent lighting. Sometimes it seems to phase-lock it (which I assume is a feature, some cameras sport this as an option in their menu which you can toggle, but mine doesn't seem to). The only two choices of frame rate are 30 and 15 fps at 640x480. I'd imagine Canon would have invested some time in making it work with both 50 and 60 Hz mains? It is very annoying, but not always apparent, seems more of a problem when the brightness changes abruptly.



25th March 2008 16:06

marxy wrote...

Fantastic demo!

I think your video camera is beating with your fluorescent lighting.

Keep up the videos they are great.

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