Total posts : 45366
As has been indicated, there are 2 provisions in Part 15 (and up north here in Canada). One, a field strength that is permitted, and aside from the difficulties in measuring that field strength, some sort of power output adjustment could be applicable to achieve that.
And then there is the 100mw input to the final stage rule, combined with limitations on the antenna/ground, where no such power adjustment (at least, above 100mw) would be allowable.
In the later Rangemasters, at least according to the documentation, I do not believe that you can adjust the power – they come standard with an auto tuning feature. I have one of the earlier ones, but tried to make sure that I stayed within the 100mw rule (both by that green light in the then-optional tuning module, which is not all that accurate, and meter readings at the specified measurement points within the unit, which are as accurate as you can possibly be).
To me, while I’m not a hardware and/or electronics technician (my major focus is on computer software/radio programming), this does not appear to be rocket science. Including if you’re going to use the 3 meter/100mw portion of Part 15. You can’t use a long ground wire which will radiate or a ground wire to a long mast, again, which will radiate – that’s just attempting to get around the rules using safety as an excuse (I’m not justifying the rules, just acknowledging that they exist). The only legal installation that will work effectively appears to be something (with that 100mw input) mounted at ground level, with a short ground wire to a buried ground rod, supplemented by radials. And some audio processing which gives your signal a bit of extra punch (I use a Symetrix 421 and an Inovonics 222).
Anything else is entering into the realm of Inspector discretion. Now, if this is just a hobby, then that’s fine; you can probably live with being told to cease and desist, while attempting to justify what you’re doing to the bitter end. But if you’re doing as some appear to be doing, and creating an actual, listened to station, known in the community, and even carrying advertising (which is a large commitment to that community) then you want to be as careful as possible to adhere to the rules that do exist today.