so ive been sitting on this NE602 and LM386 combo for like 6 months just sitting in a parts drawer and finally decided to just do it last weekend. followed the basic circuit from EMRFD, wound my own toroid for the input filter which was honestly the part i was most nervous about since i always screw up the turns count somehow, but this time i counted twice and it came out pretty close.

got it all stuffed into a mint tin which i know is kind of cliche but whatever it works and the shielding isnt bad. tuned up around 7.1 and was pulling in SSB stations pretty clearly considering theres no AGC and just a volume pot on the output. audio is a little hissy and i think i need to look at the gain staging, the LM386 at full gain is pretty rough. but honestly im just excited it works at all because my last attempt at a receiver never got past the oscillator stage

anyone played with adding a simple audio filter to one of these? ive seen some guys put an active low pass after the 386 and it cleans things up a bit. also curious if theres a better audio amp chip to swap in, the 386 has a reputation for being noisy

congrats on getting it going, the 40m DC receiver is a rite of passage honestly. the 386 noise thing is real, there's a few tricks though — make sure you have a 10 ohm resistor and 0.047uF cap from pin 7 to ground, a lot of people skip that and it makes a noticeable difference. also bypass the supply pin hard with a big electrolytic and a small ceramic right at the chip.

for a better audio stage some people swear by the LM4562 op-amp in a non-inverting config, lower noise floor and you can actually shape the response easier. i did something similar on a 80m receiver i built last winter and the audio went from tolerable to actually pleasant. an active audio filter doesnt need to be complicated either, a simple twin-T notch tuned around 700hz does wonders if SSB is your thing, kills a lot of the crud that slips through.

the toroid winding anxiety is real by the way, i still count out loud and move a piece of tape along to track the turns like some kind of ritual

nice work dude. mint tin builds have a charm to them, dont let anyone give you grief about it. i built a similar thing a couple years ago and ran it for months before i moved on to a more serious project. the 602 is a great little chip for this kind of thing.

one thing i noticed with mine was that i was getting a lot of breakthrough from a strong AM station nearby, ended up having to add another stage of filtering on the front end. depends on your location i guess, if youre near any AM broadcast towers it can be a real headache with a direct conversion design. just something to keep in mind if you start hearing weird stuff on frequencies you wouldnt expect