so ive been going down the QRP rabbit hole for about three months now and i finally finished my first scratch build — a 40m CW rig loosely based on the NorCal 40 design but i kind of went my own direction with the PA stage. running about 4 watts out which im pretty happy with considering where i started.

my question is about efficiency. im measuring somewhere around 60-65% from the PA and i keep reading that good Class E designs can hit 90% or better but honestly i dont know if thats a realistic target for a beginner build or if those numbers are more like theoretical best case. the rig gets warm but not hot, battery drain feels reasonable on my 3ah lipo pack, and ive made contacts out to about 800 miles on it which felt amazing.

should i even be chasing better efficiency at this point or is 60% fine for casual portable use. i mostly do parks stuff and occasional backpacking trips so battery life does matter to me but im not sure its worth tearing into the PA again if the gain is marginal in real world use.

60-65% is honestly pretty solid for a first build, dont beat yourself up over it. Class E is great on paper but getting it right requires pretty careful component matching and the switching waveforms need to be really clean or you just end up with a hot transistor and a mess on the spectrum. ive seen guys with way more experience than either of us struggle to break 75% reliably in a hand-built rig.

for backpacking where every gram counts the efficiency does start to matter more just because of battery weight, but at 4 watts out with 60% you're pulling maybe 6-7 watts from the battery which on a 3ah pack gives you a decent operating window depending on your duty cycle. if you're doing CW and not hammering it constantly you're probably fine. i'd spend more time on antenna work honestly — that'll do more for your contacts per milliamp than squeezing another 20% out of the PA stage.

800 miles on 4 watts is awesome, what antenna were you using for that. im also building my first qrp rig (a bitx40 kit, not scratch built like yours) and im trying to figure out what kind of portable antenna setup makes sense for parks activations. did you wind your own toroids for the output filter or use premade ones