so i finally bit the bullet and built one of those QCX mini kits from QRP Labs and honestly i was kind of bracing for disaster because my soldering hasnt been great lately but it actually came together pretty well. got it aligned and on 40m it's putting out just under 5 watts which i guess is right where it should be.

took it out to the park last weekend with a random wire and a 9:1 unun i built a while back and made like 4 contacts in about an hour and a half which felt amazing considering im running the same power as a nightlight basically. one guy in ohio actually came back to me on the first call which i was not expecting at all.

anyway my question is more about efficiency and battery stuff. right now im just using a 3s lipo i had from an old rc project, runs the rig fine but i feel like im not thinking about this the right way. like should i be more worried about the mah capacity or the discharge rate for something like this? and is there a point where the voltage dropping off as the battery drains starts to mess with the output power noticeably? i know some rigs are more picky about supply voltage than others but i dont really know where the QCX sits on that.

also curious if anyone runs these things with solar, seems like the natural next step for portable ops but i dont know where to start with that

congrats on the first successful build, that always feels good. the QCX is a pretty solid design for getting into QRP, Hans does good work.

on the battery question -- for something like that rig pulling maybe 800mA to 1A on transmit, you honestly dont need a huge capacity pack for a few hours of casual operating. a 2200-3000mah 3s should get you through a solid afternoon. the discharge rate thing is really more of a concern for stuff that spikes hard on transmit like an FT-817 or something with a bigger final, the QCX is pretty gentle in comparison.

the voltage droop question is actually worth paying attention to though. the QCX finals are pretty efficient but the output will fall off some as voltage drops, especially once you get below like 11v on a 3s pack. not dramatically but you'll notice it on the wattmeter. just keep an eye on it and dont let it sag too much. some guys add a little voltage display to their portable kit just for that reason.

solar is great but you kinda need to think about regulation -- a cheap mppt controller and a small panel works fine, just dont let the panel voltage float too high into the rig directly. seen guys fry stuff that way

ohio on the first call with 5 watts is honestly a great sign, 40m can be really good for that kind of range especially in the evenings. i had a similar experience when i first started doing POTA with my ft818 and it kind of rewires how you think about power.

i cant help much on the battery chemistry stuff but i will say that once you go down the solar rabbit hole you kind of dont come back lol. i use a bioenno 10ah lifepo4 now and a little 20w panel and it basically means i can just stay out all day without thinking about it. lifepo4 holds voltage really flat compared to lipo which is nice for exactly the reason the other guy mentioned