I broadcast on 1620 AM and am quite happy with that, and I have no intention of adding an FM for mass consumption. However ....
I am now providing audio for the public access cable channel in my town. This costs me nothing except equipment to make it work, and I'm on in every household with cable TV which is pretty much everyone as there's no OTA TV around here. So I set up an AM receiver and some switching, cabling, etc to interface it to the TV system over at City Hall (the only thing they broadcast on public access is city council meetings twice a month). The trouble is AM reception in the room where the equipment is located is marginal at best. The Dayton Am monitor I set up originally was so sensitive it picked up noise from every piece of equipment in the room. After playing around with varying radios, getting a long cable to move the radio far away from any equipment, it's passable, but not what I consider good. This room has a rack full of TV equipment, TV set, several computers, ancient flourescent lights, etc so the interference is horrible. Reception is fine in other parts of the building, but since it's a 100+ year old historic building, messing around in it too much is frowned upon. If I could put the receiver in another room and run 100+ feet of cable, I'd be good but that physically wont' work out. I do know that the interference is getting in through the radio reception, not in the audio cables/switching from the radio to the gear.
I'm considering FM. I've done no research at all on FM Part 15 transmitters. All I know is range is quite limited and the rules are for field strength not input power. City Hall is about 450 feet from the attic window where I have my AM transmitter set up. It would be easy to set up an FM transmitter in this same window. It's line of sight from my attic window to city hall, although by site a straight line would hit just above the office where I would set up the receiver, but it'd be mighty darn close. Could I expect a Part 15 FM transmitter that doesn't cost a fortune to hit City Hall 450 feet away? The receiver would be located up out of harms reach from bystanders and I could set up an indoor antenna if necessary. I don't need stereo, but I need a solid signal and I think FM would easily get me out of the interference from stuff in the room zone.
Is this a realistic expectation for an FM transmitter? And what would anyone recommend? this would basically be an FM studio to city hall audio link that I would not advertise the frequency, etc.
I have a solid as heck AM signal there -- sounds fantastic once I get out of the room full of gear, but all that equipment is just too much interference competition for my signal.
Tim in Bovey
Iron Range Country