so i finally got my first scratch built QRP rig on the air last weekend, its a simple 40m CW transceiver based on the Pixie kit design but i wound my own toroids and substituted a few components i had in the junk box. got about 500mw out of it which i know is low even for QRP but im pretty happy with how it came together on the bench.

managed a contact about 200 miles away which felt amazing honestly, the other op was running like 100w so i know thats not exactly a fair fight but still. my question is about efficiency, im running off a 9v supply and the PA stage gets pretty warm after a few minutes of key down. is that normal for a class C amplifier at these power levels or should i be looking at my biasing? i dont really have a proper dummy load either, just a bunch of resistors i cobbled together, wondering if thats throwing off my measurements.

also if anyone has suggestions for a next build that steps up a little, maybe to 5w on a couple bands, id love to hear what kits or designs people have had good experiences with. im not opposed to building from a schematic either if the documentation is decent.

congrats on that first contact, seriously 200 miles at 500mw is a solid start especially on 40m during whatever conditions youre dealing with. the warmth on the PA is pretty typical for a class C design running that hard, those little TO-92 or similar transistors dont have great thermal mass. if its just warm thats fine, if its hot enough you cant keep your finger on it for more than a second or two i'd look at whether youre biased correctly or if the final is actually seeing the right load impedance. a cobbled together dummy load can absolutely mess with your readings, even small inductance in those resistors changes things at HF. worth spending an hour building a proper one, fifty ohm non inductive is what you want and there are plenty of simple designs online using those thick film resistors.

for next build honestly the QCX from QRP Labs is hard to beat, Hans does great work and you learn a ton. or if you want something more adventurous look up the BITX40, the documentation is actually really good and the community around it is huge.

im in basically the same boat, built a 40m rig last year from a design in SPRAT and it took me forever to figure out why my output was lower than expected, turned out i had one of my toroids wound wrong, like the number of turns was off by two and it was killing the efficiency. might be worth double checking all your coil counts especially if you substituted anything from the original design. also 500mw making a 200 mile contact is honestly pretty cool, i remember my first qrp qso felt way bigger than any of the 100w contacts i'd made before haha