Total posts : 45366
Might be wise, but AM has some potentially confusing rules as well. The FCC can come at you for excessive field strength in broadcast band AM radio too.
If you run the numbers for legal field strength for Part 15 FM, you’ll see you can’t get a practical signal at much more than 200 ft. or so. Beyond that it drops of quickly and dramatically. But, again, a great deal depends on the RECEIVER … and also whether or not you broadcast a stereo signal … because as you’ll find in other threads, the stereo pilot signal sucks up a lot of energy.
Compare to AM which drops off slowly and has greater (I would say much greater) potential range. Antenna tuning for AM radio is very critical as is a good ground (my gear is on my boat grounded to the sea), and even then the signal is more prone to interference, everything from Christmas LED lighting to auto traffic to buildings to power line boosters to atmospheric conditions, and more, it’s still what I would consider ‘acceptable’ at ranges up to nearly a mile in certain conditions.
Most modern auto radios work well. If I go down most streets in town, I can hear it well enough, but when I turn a corner I can lose it for a bit, or when I pull into a parking space next to the grocery store, which has hundreds of florescent lights and blocks the signal, it gets a lot of noise. But if it were legal Part 15 FM, the signal would barely get off the dock. AM is more difficult to deal with, but again the payoff is more overall range.