Here's a case where folks need to understand the other alternatives out there. I no longer will do Part #15 FM, except maybe to test a transmitter, since anything unlicensed FM where I am is so bastardized, due to the political climate today. So, I'm doing both the permissible Part #15 AM ways, radiating 100mW MAX OUT, (If not less.), to a 10ft antenna and Carrier-Current, coupling to the power lines. Unfortunately, with Radio Systems and LPB, Inc., both gone, there's few alternatives to what's out there in Carrier-Current, except to roll your own gear. (It's been done.) At least, there are several radiating AM transmitters out there that are FCC approved, albeit not cheap. (Some have rolled their own here as well.) For FM, the market is just littered with these cheap Part #15 transmitters, most being used to transmit net streams and satellite radio. (87.9FM seems popular for that when you drive around.) However, there range is from about 200ft with a decent car stereo, to maybe 50ft to a crappy portable.
Anyway... Looks like there certainly a market out there for Part #15 radio transmitters, but folks need to be aware of just what's out there. However, there seems like there is nothing on mainstream media that points out AM Part #15 gear, just some FM stuff, like C Crane, par example.