Any chance of using commercial 10.7 MHz IF transformers?

I was wondering what is the advantage, if any, of taking the output as RF from the tank rather than taking the output, either RF or audio from the low impedance Emitters?

For any interested in trying this citcuit. Elenco makes a MW kit with all parts necessary which uses a TA7642 as the front end. On one of the receivers which I constructed I removed the TA7642 and with a few modifications reconfigured the wiring to create the receiver in this thread. https://shop.elenco.com/consumers/two-ic-am-radio-kit.html

After the old Radioboard died I was fortunate to discover this site and was surprised to see one of my regen receivers shown in the schematic below as the first post . For the past two years I have been a frequent visitor largely because of the posts on this site from the talented contributors whose names I recognize from the old Radioboard days. I don't have any text information from the old Radioboard but I do have all my old schematics saved on a variety of computers. I'm hoping that some might try building a few of the most unusual circuits so that I can obtain their input on any improvements that might be made.

The link that you provided was a compilation of using an external Q multiplier and then using the LM386 in different modes i.e. combination high gain audio amplifier rf detector, rf detector, rf detector buffered. In all these modes, the AF gain is extremely high without the need for an external detector. The audio gain may be easily controlled by using a 100 Ohm variable resistor in series with the 10uF capacitor from Pin 1. This might also help tame any stability issues that could arise from layout because of the extremely high gain. Regarding sensitivity, my experience has been that using a regenerative receiver any potential losses are compensated for by the regeneration, which means that even at higher SW frequencies losses in the ferrite rod inductors which I use are compensated for. It is only necessary to use more regeneration as the frequency rises. It has been a while but I believe that I continued to use circuits numbers 4 and 5 most often. Circuit number 4 is using the LM386 both as an RF detector and normal audio amplifier. Circuit number 5 uses the LM386 only as an RF detector.

"How about the interaction of the RF tank preselector and the LO in your receiver? Does the RF tuning affect the LO tuning?" I have not noticed any interaction. As you noted the NE602 likely provides ample isolation. You had mentioned previously that you went away from commercial IF transformers and wound your own toroidal transformers. In my superhet I use a standard red MW local oscillator transformer in parallel with a 10 pF capacitor to achieve an IF frequency of 1.7 MHz which is tunable. I believe you have used these before in other circuits but I was wondering if you had tried them in your present receiver?

Just for your interest, a few years ago I built a superhet SW receiver using a regenerative IF using the LM386 audio amplifier as the only active component of the regenerative IF. The LM386 is set up with its front end as a Colpitts oscillator and its remaining circuitry as an audio amplifier. The superhet used both high side and low side injection to cover the frequency range of 3.4 MHz to 10.2 MHz. You asked me a question about it on the old Radioboard regarding the front end preselector. I have forgotten what your question was but my answer was that the background noise would pick up as the preselector was tuned to the proper high side or low side frequency. I used an IF frequency of about 1.5 MHz to maximize SW band image rejection. The frequency numbers on the schematic below indicate an IF frequency of 1.7 MHz with a local oscillator frequency varying between 5.1 and 8.5 MHz. I have not done an in depth look at any interaction between the local oscillator frequency and regeneration setting when tuning, but the regeneration setting seems very stable when tuning over the full range and does not need readjusting. The receiver performs very well and using only the ferrite rod front end inductor L1 and no external antenna I use it frequently to receive CW and SSB on the 80 and 40 meter ham bands up and down the East coast of the U.S. and Canada.

"The circuit does open to door to using the noisy regen circuit for super-regeneration experiments. You would just need to experiment with different values of capacitor connected across the differential pair, eliminating the loudspeaker obviously." I have always thought since I first came across the "noisy regen" circuit that the name was a misnomer and that the original designer used a bypass capacitor which was too large and the circuit had simply become a superregenerative receiver.

Mine was used with a tuned circuit from 3 to 10 MHz. With the values shown and a 9V supply there is complete regeneration control over the full tuning range. I chose a 100K value for the output load resistor to get as much audio gain as possible when the output was going into a high impedance input audio amplifier. It might be necessary to lower this resistance under other circumstances.

I built a similar shortwave regenerative receiver which used the two transistor's Base-Emitter intrinsic capacitors as a Colpitts oscillator. Performance is very good. Using 3 inch ferrite rod inductor in the tuned circuit I listen most evenings to 80 and 40meter SSB up and down the East coast of the U.S without the need for an external antenna or ground. https://groups.io/g/TheNewRadioBoard/topic/strange_to_me_regen_cct/100532634?p=,,,20,0,0,0::recentpostdate/sticky,,,20,2,0,100532634,previd%3D1691466224508899524,nextid%3D1681129345133277562&previd=1691466224508899524&nextid=1681129345133277562

"Second, 56 dB audio gain is inadequate for use with a loudpeaker." "To get additional gain quick, I went ahead and put a 10uF cap across pins 1 and 8 of the LM386 to boost gain to maximum. It appears to remain completely stable." It is possible to significantly increase the gain of the LM386 by placing the 10 uF bypass cap in series with a resistor and connecting this combination between Pin 1 and Ground. A 3 Ohm resistor will provide 74 dB gain.

The reactance of the 4.7 uF audio output capacitor is about 33 Ohms at 1,000 Hz. The audio output amplitude can likely be increased slightly by raising the value of this capacitor.

Edit: Error in previous reply. The reactance of audio output capacitor C13 is about 30 Ohms at 1,000 Hz. The audio output amplitude can likely be increased slightly by raising the value of this capacitor.

The reactance of audio output capacitor R17 is about 30 Ohms at 1,000 Hz. The audio output amplitude can likely be increased slightly by raising the value of this capacitor.