I might be talking crazy talk here but...
I know often we talk about how to distribute audio to a remote network of transmitters. Many will use an FM Part 15 to distribute audio to part 15 AM transmitters, or use internet, etc. Suddenly, while answering Radioboy's blog this morning, I thought "Hey, why not a Marti unit?"
For those who don't know, a Marti is an FM transmitter that is used by commercial radio to broadcast from a remote location -- the high school basketball game, sale at the hardware store, grand opening at the super market, etc. They are sold in various frequencies, and they've been in use for probably 40 years or more. Marti units go way back to tube models, and of course there are modern solid state units as well. They're built like tanks and run on AC or 12 volts. Generally 20-40 watts depending on model or condition. They put out a very clear FM signal (not stereo) that is used for commercial broadcasting. I've used one in the biz since the 70's. I use one in my present day commercial radio broadcasting. It's presently putting out about 25 watts, we use a portable 1/4 wave antenna and get signal back to the station from up to about 10 miles out. We do much better with the yagi antenna, or if we can get some height. This could easily send a clear signal to an unlimited number of Part 15 transmitters within a ten mile or more radius with the right marti transmitting antenna. Although Marti units come with matching receivers -- all crystal controlled -- a typical $10 scanner from a thrift store will usually tune in Marti frequencies and can easily be used as the receiver at the part 15 transmitter. The one we use at work is on 161.700 MHz and 10 miles away my cheap Realistic scanner picks it up at home no problem.
Now that so many radio stations are moving to other types of ways to do their remotes (mostly internet) Marti units come up on the used market pretty cheap, especially the older ones from the 70's (no one wants to haul them around). They do require an FCC license but I believe that's a matter of filing out a form and sending in a filing fee. They're considered "RPU Units" (remote pick up). We have in a pinch used one to send audio to our commercial FM and AM transmitters from our studio when our STL or line to the AM was on the fritz. This makes a Marti an STL (studio-transmitter link). Obviously this would work, as it's done in commercial radio every day.
Plus a typical Marti has 4 inputs -- line and mic, so you could even feed remote transmitters and use the Marti as your mixer, too. Feed a computer into one channel, a mic into the other, and you're on! What you need is a Marti RPT-25. They're the least expensive right now it seems. I see they're all over ebay from a few bucks to a couple hundred depending on condtion. New ones are a couple thousand for a system. But simple receivers at remote locations could all receive the signal -- you could have a very solid way to feed a huge network of part 15's with minimal cost compared to other options!
Tim in Bovey