I'm someone who has worked in broadcasting since 1964. Before that I experimented with Knight Kits, Lafayette kits and whatever else was available. The Part 15 broadcaster of today has some unique advantages I didn't have as a teenager...solid state electronics, manufacturers who make Part 15 transmitters that really work, coils, plans for antennas that are legal and go great distances on 100mw, and most of all the countless how-to's from the internet. 100mw is a lot of power if you use it right! I'd also like to share a few thoughts from my days of professional broadcasting about the FCC.
1.During the CB revolution of the 1970s it became very hard for the FCC to chase down everyone using what was termed "foot warmers", offensive language and the interference of one operator over another. This had a numbing effect on the FCC that they couldn't regulate everything and they kind of gave up trying ...who could blame them...people went crazy. Instead, today's FCC serves the public by answering complaints about amateur radio interference to TV sets, unauthorized powerful transmitters that radiate harmonics up the audible spectrum, and increasing complaints about a growing number of illegal FM stations that serve a particular listening audience in large metro areas.
2.The FCC is more concerned about complaints regarding interference or a reported interference which they will investigate. Notice I said a reported interference. This applies to FM more than AM....a legal AM 100mw signal is easily lost in the clutter of noise from electrical towers. 10 watt FM exciters were easily ordered from places like Broadcast Supply West in the 70s & 80s with the capability to range from 1 to 12 watts power with only a 30" whip antenna attached directly to the back of the transmitter setting in a garage on a workbench giving coverage of up to 4 miles. When you put it in the attic you could cover 15 miles by raising the height just 10 more feet. I know this because I owned one of these before selling it to Harris Radio's used equipment store in Indiana. Believe it or not, that FM exciter I bought 26 years ago wasn't all that much fun because there weren't any challenges about engineering it for more distance. If you are using an AM SSTran or Hamilton and using it correctly you probably have nothing to worry about unless you have a neighbor who just wants to complain. It certainly won't have anything to do with interference. Another mistake young people and beginners make while "endless testing" is playing the same record over and over because it sounds good on the radio. This always gets people's immediate attention and being good citizens with a lot of time on their hands they'll call the local FCC office because nothing like that is normal on the AM band. Be as professional as possible! Again, if you program responsibly (no paid commercials) (that means a log and inspections from the FCC), abusive language, any radical\racist or off the wall political programming will almost guarantee you'll wind up on the FCC radar but not for interference but irresponsible programming. The Fairness Doctrine died in 1988...but I can guarantee that's it's very much alive for the unlicensed Part 15 broadcaster.
3. An inexpensive RF meter is a great way to guage efficiency in signal strength. The old story about the 1973 CB radio antenna mounted on top of a Volkwagen Beetle is true. The individual did get tremendous range at night (state to state on 5 watts) due to atmospherics and the beautiful reflectivity\contour of the VW's perfectly formed roof acting as an almost perfect ground plane. An RF meter will measure very little on a vertical pipe or wire cemented into the ground unless you connect it physically with an alligator clip because it's just a grounded vertical metal pole. It will measure a dramatic jump when the meter is put close to the ground and moved over the array of radials of the ground system and the actual reflection can be seen on 10\10 foot radials. The 10 foot antenna with the coil (a must) recommended by the manufacturers works in concert with the ground system as a reflector thus giving AM its local daytime coverage (nightime is different due to the lowering of the Ionosphere for AM's state to state coverage). The vertical part of the iron, copper or aluminum mast (and it should be no longer than 3-4 feet) acts to support the antenna\transmitter and makes the connection to the ground array. The amount of radiated energy is "extremely negligible" on the metal support pole until you get to the bottom and start seeing the meter jump dramatically as it comes within 12" of the ground system array. It also should be noted that the highest reading comes when you hold the RF meter high in the air adjacent to the antenna (5-10 feet away). You're actually seeing the highest RF from the antenna and you'll always see that whether you have a ground system or not but you won't get "real" coverage w/o the added ground system (and the coil of course). If you want coverage with a Part 15 transmitter you must have both ground radials and the antenna working together with the ground reflection and the radiation from the antenna.
Hope this is helpful especially to those young people with the desire to become engineers, radio announcers or eventually leading to owning your own station someday.
1.During the CB revolution of the 1970s it became very hard for the FCC to chase down everyone using what was termed "foot warmers", offensive language and the interference of one operator over another. This had a numbing effect on the FCC that they couldn't regulate everything and they kind of gave up trying ...who could blame them...people went crazy. Instead, today's FCC serves the public by answering complaints about amateur radio interference to TV sets, unauthorized powerful transmitters that radiate harmonics up the audible spectrum, and increasing complaints about a growing number of illegal FM stations that serve a particular listening audience in large metro areas.
2.The FCC is more concerned about complaints regarding interference or a reported interference which they will investigate. Notice I said a reported interference. This applies to FM more than AM....a legal AM 100mw signal is easily lost in the clutter of noise from electrical towers. 10 watt FM exciters were easily ordered from places like Broadcast Supply West in the 70s & 80s with the capability to range from 1 to 12 watts power with only a 30" whip antenna attached directly to the back of the transmitter setting in a garage on a workbench giving coverage of up to 4 miles. When you put it in the attic you could cover 15 miles by raising the height just 10 more feet. I know this because I owned one of these before selling it to Harris Radio's used equipment store in Indiana. Believe it or not, that FM exciter I bought 26 years ago wasn't all that much fun because there weren't any challenges about engineering it for more distance. If you are using an AM SSTran or Hamilton and using it correctly you probably have nothing to worry about unless you have a neighbor who just wants to complain. It certainly won't have anything to do with interference. Another mistake young people and beginners make while "endless testing" is playing the same record over and over because it sounds good on the radio. This always gets people's immediate attention and being good citizens with a lot of time on their hands they'll call the local FCC office because nothing like that is normal on the AM band. Be as professional as possible! Again, if you program responsibly (no paid commercials) (that means a log and inspections from the FCC), abusive language, any radical\racist or off the wall political programming will almost guarantee you'll wind up on the FCC radar but not for interference but irresponsible programming. The Fairness Doctrine died in 1988...but I can guarantee that's it's very much alive for the unlicensed Part 15 broadcaster.
3. An inexpensive RF meter is a great way to guage efficiency in signal strength. The old story about the 1973 CB radio antenna mounted on top of a Volkwagen Beetle is true. The individual did get tremendous range at night (state to state on 5 watts) due to atmospherics and the beautiful reflectivity\contour of the VW's perfectly formed roof acting as an almost perfect ground plane. An RF meter will measure very little on a vertical pipe or wire cemented into the ground unless you connect it physically with an alligator clip because it's just a grounded vertical metal pole. It will measure a dramatic jump when the meter is put close to the ground and moved over the array of radials of the ground system and the actual reflection can be seen on 10\10 foot radials. The 10 foot antenna with the coil (a must) recommended by the manufacturers works in concert with the ground system as a reflector thus giving AM its local daytime coverage (nightime is different due to the lowering of the Ionosphere for AM's state to state coverage). The vertical part of the iron, copper or aluminum mast (and it should be no longer than 3-4 feet) acts to support the antenna\transmitter and makes the connection to the ground array. The amount of radiated energy is "extremely negligible" on the metal support pole until you get to the bottom and start seeing the meter jump dramatically as it comes within 12" of the ground system array. It also should be noted that the highest reading comes when you hold the RF meter high in the air adjacent to the antenna (5-10 feet away). You're actually seeing the highest RF from the antenna and you'll always see that whether you have a ground system or not but you won't get "real" coverage w/o the added ground system (and the coil of course). If you want coverage with a Part 15 transmitter you must have both ground radials and the antenna working together with the ground reflection and the radiation from the antenna.
Hope this is helpful especially to those young people with the desire to become engineers, radio announcers or eventually leading to owning your own station someday.