so ive been building this 40m CW transmitter from a design i found in an old ARRL handbook, the one from like 2003 or so. crystal controlled, running a 6L6 in the final. got the thing oscillating and i can hear my signal on the receiver across the room but the output just feels low, maybe 3-4 watts when i was expecting closer to 15 based on the original design specs.

ive checked the plate voltage and its sitting around 280v which should be fine, grid bias looks okay, and the pi network is tuned to a fairly sharp dip on the plate current. neutralization i honestly am not 100% sure i did right, the tube is triode-connected in some variants i read about so maybe thats not even the issue.

the thing that really bugs me is the plate current at dip is only pulling like 55ma when loaded. i feel like that number should be higher. could be the tank coil, i wound it myself and im not totally confident about the number of turns i ended up with after trial and error. anyway anyone dealt with this on a similar build, would love some ideas before i start poking around with the RF probe again

the coil is almost certainly your problem if you wound it yourself and werent super precise about it. a tank coil thats off by even 10-15% inductance will throw off your pi network matching and youll never get proper load on the final. what gauge wire did you use and how many turns, whats the coil form diameter? if you can measure inductance with even a rough LC meter you can sanity check it against what the design calls for.

also 55ma at dip on a 6L6 with 280v on the plate does sound light. what does the grid current look like when youre driving it, if youre even measuring that. sometimes the driver stage isnt putting enough RF into the grid and the final just isnt being pushed hard enough regardless of everything else being right. the 6L6 needs a decent swing on the grid to really open up. id check your driver output before assuming the final itself is the issue.

had almost the exact same thing happen when i built a transmitter a couple years ago, different tube but same kind of frustration. turned out my grid leak resistor value was wrong, i grabbed the wrong one from my junk box and it was biasing the tube too far into cutoff. worth double checking all your passives around the tube socket, its easy to grab the wrong resistor when youre in the middle of a build and not really paying attention.