I am now considering the possibility of broadcasting Richmond District Radio programs on AM or a combination of AM and FM in simulcast.
I like AM for a variety of reasons. Part 15 rules for AM puts constraints on power and antenna system, but not on field strength, which means it’s technically possible to get a signal farther afield than an FM signal under the same rules, given the height I have available to me.
AM is relatively simple technology. Simple means reliable. Now, I don’t expect listeners to build their own radio receivers, but with the AM band it’s certainly doable. In a perfect world, we would have community radio building meetup nights.
Modern AM is not known for its high fidelity sound, this is more an issue of narrow IF bandwidth radios that are common nowadays. But, since I plan on airing mostly spoken word this would not the same problem as it would if our program consisted mainly of music.
A downside of going AM is that I don’t have any AM transmitting equipment whatsoever (not the case with FM). Any AM transmitter would have to be purchased, or more likely, constructed. Transmitters for personal use, not for sale, do not require FCC certification – although they must employ good engineering practices throughout and your output must meet spectral purity requirements.
I’ve tried to separate marketing hype from truth regarding coverage area possible with Part 15 AM. I believe that with a high enough antenna and decent ground system I have a good chance of putting a usable signal across my target area of north side of The Park to Lake Street, from USF west to Park Presidio.
Some of the obvious problems are interference from numerous noise sources. Not only power lines, but electric buses, computers, and the generally high urban radio noise floor. Also, nighttime broadcasts might suffer significant competition from distant stations.
Just thinking, I could equip my IC-725 MF/HF radio with the UI-7 board (which enables AM transmit). Then, in an emergency, I could run the ICOM on broadcast band frequencies.
If it weren’t for the pesky rules, I could use the Icom as a carrier exciter for everyday operation. I’d need to assemble an amplifier and modulator stages. Hmmm… just thinking…