so ive been working on this little crystal controlled 40m transmitter for a few months now, just a simple 7MHz thing based loosely on the QRP-Labs style circuit but i didnt just copy it, wanted to understand what i was doing so i built it mostly from scratch on a piece of copper clad board. anyway got it all assembled last week and it keys fine, the sidetone sounds good, the crystal is oscillating at exactly where it should be according to my frequency counter.

problem is im only seeing like 200mW out when i was expecting to be closer to 1W maybe a bit more. ive got a BS170 as the final and im running it off 12V. the gate bias seems right, ive checked the drain current and its sitting around 80mA which feels reasonable but honestly im not totally sure what im aiming for there. the low pass filter after the PA stage is a 7 element chebyshev design i wound myself, toroids are t50-2 cores. wondering if my winding is off or if the problem is something upstream, hard to tell without a proper spectrum analyzer which i dont have.

anyone been through this kind of thing with a similar build? i can post the schematic if that helps

yeah post the schematic, hard to say much without it. but a few things come to mind -- 200mW from a single BS170 at 12V isnt actually that far off depending on how the drive level looks. those little mosfets are pretty sensitive to gate drive, too much and you saturate early and waste power as heat, too little and youre just not turning them on properly. what does the drain waveform look like if you have a scope? even a cheap one will tell you a lot. if you dont have a scope then youre kind of flying blind on RF stuff like this unfortunately.

also your toroid winding counts matter a lot on 40m, even being one turn off can shift the filter response enough to cause some loss. did you verify the filter with anything or just wind it to the design values and hope for the best? i've done that plenty of times and usually it works out close enough but sometimes it doesnt

the BS170 is the issue imo, or at least part of it. ive built a few QRP rigs with those and they can do 1W but you kind of have to baby them and get everything tuned just right. a lot of guys swap to the IRF510 if they want more headroom but thats a bigger step up and you have to redesign the matching network. for a first transmitter build 200mW is honestly not bad, you can work people with that on 40m CW if conditions are decent, ive done transatlantic with similar power levels. dont get too hung up on the number before you actually try it on the air