You didn't find a separate 'volume control' to be essential? Turning down the regen to compensate for audio level degrades the selectiivity. Actually, i have seen many published vintage circuits with no audio level

control, and always wondered how that worked out. - H M

I found the misplaced radio. Photo of slide box radio at http://www.flickr.com/photos/grahamh_pix/8357427818/in/photostream . Other photos there as well.

Graham

This type of circuit, reflexed stage plus two audio transistors, without the regen and running a crystal earphone was around in the late 60s. Several at my high school built it as a first solid state radio (AM B/C band). I refined mine by adding regen and using a ferrite rod antenna. It eventually was built into a 36 exp Kodak slide box on tagstrip with fixed regen set to just not oscillate at around 1600KHz. Power was a 9V battery. Both the earphone and battery lived in the box when not in use. It got all the Sydney station from the Hornsby area. It still exists but the earphone has died.

Afternoon Alan

I have learnt a lot from your informative website.

Could you provide info on the colour code of your toridal core. I assume it it is ferrite. I purchased a 40mm uncoated ferrite from Jaycar.I have built your receiver but it is not tuning across the bandspread as all that is coming through is ABC fixed shortwave and breakthrough from ABC FMJJJ.

Any comment appreciated.

Regards

Dennis

Bert,

Maybe, the gain of the device might be different enough to cause problems. Generally changing the feedback winding should allow you to compensate.

Regards,

Alan

Could the type of the transistor that I used (2N3904) the root of the hysteresis problem? Huh, have to build it again to see the effect.

Bert,

That's odd mate, I had no problems with hysteresis of the regeneration with this receiver... Reducing the coupling as you did would have been my first suggestion. The 5 K pot should be more than enough to let it drop out of oscillation, in fact it generally fights you trying to force it to oscillate.

You could try putting a 1K pot in the emitter of the detector, it should be possible to control the oscillator gain and set it just sufficient for operation across the bands of interest.

Regards,

Alan

Hi Alan,

When using this receiver, I found the regen control has some "hysteresis" effect, which makes it always oscillating when I want it to receive shortwave stations.

Very annoying, I changed the feedback loop count, changed the feedback capacitor (from 1nF to 100pF), but does not help at all. One weird thing is that, after changing the components, the operating position of the regen knob is identical! What can I do to eliminate the hysteresis effect?