so i've been wanting to build something from scratch for like two years now and i finally just sat down and did it over the long weekend. threw together a direct conversion receiver for 40m based on that EMRFD design, nothing fancy, just manhattan style construction on a scrap of copper clad i had sitting around.

the thing actually receives SSB pretty well, way better than i expected honestly. i mean its noisy and the audio chain definitely needs work, probably the op-amp stage i slapped in at the end cause i didnt have the right part and just used whatever was in my junk box. but i can pull in stations, like real ones, EU pile ups last night which blew my mind considering the whole thing cost me maybe 8 bucks in new parts.

the LO is just a colpitts oscillator and it drifts a bit when things warm up but stabilizes after maybe 10 minutes. wondering if anyone has gone down the rabbit hole of adding a PLL or even just a good VXO to one of these to clean it up. or do i just live with the drift and call it character

the drift thing is super common with those colpitts designs, thermal stabilization takes forever especially if you didnt use NP0 caps in the tank circuit. that's usually the first thing to check. swapping in NP0 or C0G ceramics for the timing caps made a huge difference on mine, almost no drift after warmup.

as for PLL, its doable but honestly for a first DC rx a good VXO with a quality toroid and some temperature compensation is a lot less headache. si5351 breakout boards are like 5 bucks now and people are doing great stuff with those for the LO, pairs nice with an arduino if you dont mind a little microcontroller stuff mixed into your RF. congrats on getting it working though, that first time you hear a real QSO on something you built yourself is a pretty good feeling

yeah the si5351 route is what i did when i built a similar thing last year, cleans everything right up. only thing i'll add is watch your audio stage gain distribution, if the noise is really bad it might be where you're placing the gain in the chain not just which opamp you used. too much gain early before any filtering and you just amplify all the crud. anyway nice work getting it on the air, manhattan style on copper clad is underrated for RF stuff