so i finally finished my first scratch built QRP rig, been working off the EMRFD book and a few youtube builds for reference. its a 40m CW only thing, probably putting out around 3-4 watts measured into a dummy load. honestly i was expecting total disaster but the dang thing actually oscillated on the right frequency and i made a contact into ohio from kentucky on the first real try which i thought was pretty cool.

anyway my question is about efficiency, im noticing the final transistor (2n2222a) gets pretty warm after like 10 minutes of operating even at this power level. is that normal or am i doing something wrong with the bias? i copied the design pretty closely from the book but i might have gotten a resistor value wrong somewhere. also wondering if anyone has tips on enclosures for portable use, right now its just sitting on a piece of plywood which works but isnt exactly field ready.

also for what its worth the receiver side is a direct conversion setup and its workable but kinda rough, lots of audio hum that i cant quite track down. might be a grounding thing. anyway loving qrp so far, wish i had gotten into building years ago

the 2n2222a getting warm isnt necessarily wrong but it depends on how you have the bias set up. those little transistors are rated for not much collector dissipation, like 500mW absolute max and thats pushing it. if your bias is set too high you could be burning a lot of power as heat instead of rf. worth checking the quiescent current with the key up and seeing if its way higher than the design calls for. EMRFD usually gives you target numbers for that stuff.

for the audio hum on the direct conversion rx, first thing id check is if its 60hz or 120hz hum because that tells you a lot. 60hz usually means youre picking up the ac fundamental somewhere, 120hz is more often a rectification issue in your power supply filtering. try running off a battery and see if it goes away, if it does then your power supply filtering needs work. if it stays then youre probably picking up hum through the antenna or a ground loop somewhere. dc rx builds are notorious for this honestly, you kind of fight it the whole time.

for an enclosure hammond makes some decent aluminum boxes that are pretty affordable and you can find them on mouser. i use an altoids tin for the really tiny stuff but for a 40m rig youre probably going to want something bigger. just drill it carefully and take your time, thats the part i always rush and regret

that ohio contact on first try is awesome, qrp really does work way better than you'd think going in. i remember being totally shocked the first time i worked someone a few states away on 5 watts, like wait that actually happened?

i dont have a ton to add on the technical side but i will say for portable enclosures ive had good luck with those project boxes from the plastic kind, not super rugged but lightweight which matters when youre hiking stuff in. some guys use pvc boxes too. whatever you do just make sure all your connectors are properly secured because ive had bnc connectors pull loose at the worst times out in the field and its super annoying to troubleshoot when youre sitting on a hill somewhere