so i finally pulled the trigger and built one of those QRP labs kits, the QCX mini on 40m. took me about a weekend spread across a few evenings and honestly it wasnt as scary as i thought it would be. got it up and running and made my first contact with it running 5 watts into a random wire out the window, guy was about 400 miles away and gave me a 559 which i was pretty stoked about for such a tiny little thing.

my question is kinda about efficiency and battery stuff. im running it off a 3s lipo i had from an old RC car hobby and it seems to work fine but i notice the battery gets warm after maybe an hour of use. not hot, just warm. is that normal or should i be worried? i dont have a fancy current meter or anything just a basic multimeter. also wondering if anyone has tips for getting more out of low power, like operating habits or antenna tricks because i feel like im leaving contacts on the table just not knowing what im doing on the air yet

congrats on the first build and first QRP contact, that 559 at 5w is genuinely solid especially with a random wire. the battery warmth is probably fine honestly, lipos do get a bit warm under load and as long as its not hot to the touch or swelling you're likely okay. the main thing with lipos is keeping an eye on the voltage -- if it drops too low during TX that can cause all kinds of weirdness with the finals. a simple cell voltage checker from amazon is like 3 bucks and super handy.

for getting more contacts on low power the biggest thing i'd say is patience and timing. find a relatively clear frequency, listen for a while, and call CQ when the band sounds like its in decent shape. early morning on 40m can be magic with QRP. also if you havent tried FT8 yet, that mode was basically made for low power situations -- you can work DX with 5w that would be near impossible on SSB. some purists don't like it but hey, a contact is a contact when you're learning

oh man i remember my first QCX build, i messed up a solder joint on the BS170s and had to resolder like three times before it would put out proper power lol. yours sounds like it went smoother than mine did. the 3s lipo should be around 12.6v fully charged which is right in the sweet spot for that radio so you're good there.

one thing that helped me a lot with QRP was learning to really listen before calling, like actually sit on a frequency for a few minutes and see if theres a pattern to how busy it gets. also CW is honestly worth learning if you havent already, even just the basics, because you can punch through conditions on CW at 5w that just dont work on phone