so ive been working on this DC receiver for a few weeks now, its based loosely on the Norcal design but ive been modifying it a fair bit. got it on the air last night and was actually picking up some SSB signals which was pretty exciting for a first attempt. the audio quality isnt great but its there.

my main issue right now is im getting a lot of LO leakage out the antenna port. i measured it at about -20 dBm which seems way too high. ive got a simple diplexer on the RF input but i dont think its doing much at the LO frequency. should i be looking at a better balanced mixer or is there a filtering approach thats more practical for a homebrew build like this. the mixer im using is just a pair of 1N4148 diodes in a ring config with a hand wound toroid, nothing fancy.

also the audio is picking up some hum that i cant track down, tried shielding the AF stage but it didnt really help. could be the wall wart power supply, im not sure yet.

-20 dBm is definitely too hot for LO leakage, you could be causing interference plus its going to desensitize your receive path if any of it reflects back. with a hand wound diode ring mixer the balance is really sensitive to how evenly matched your diodes are and the symmetry of the toroid windings. worth trying to select your 1N4148s for matched forward voltage, even a small mismatch kills the balance. ive built a few of these and honestly getting below -40 dBm with hand selected diodes and careful winding is doable but takes some iteration.

for the hum i'd suspect the supply first, those cheap wall warts are pretty noisy. try running it off a battery and see if the hum goes away, that'll tell you right away whether its the supply or something else like a ground loop in the audio stage.

yeah the battery test is the first thing id do for the hum, same problem on my NE602 build last year drove me nuts for days and it was just the supply the whole time. also on the LO leakage thing, have you tried adding a small cap across each diode to help with balance, seen that trick in the EMRFD book somewhere. might be worth a look