Total posts : 45366
You raise some good points and offer good advice. Allow me to take this as a chance to express opinion regarding part 15 in general.
My first opinion is that part 15 AM and FM was never intended to allow the range necessary for community broadcasting. The experience which you have previously shared about your FM activities and your neighbors as listeners is great but what you are doing is a long way from serving a community. Please don’t read this wrong…my thoughts about a community extends beyond just a few neighbors and I do not mean to detract in any way from your efforts and success.
My next opinion is that the FM rules intended to provide a means to interface with existing receivers in the home. Just as I am convinced that part 15 rules for AM were to provide for “phono oscillator” applications I am also convinced that the FM rules were written with the same intent. In the era since 1937 when as best we can determine the part 15 rules were written for AM up to the late 1950s there were no kits or devices available to the hobbyists other than manufactured phonographs which included the oscillator. The KnightKit AM transmitter kit which became available around 1955 opened the door for the experimenter as did subsequent articles for roll your own AM transmitters published in Popular Electronics and other magazines. What was originally intended to be a novel addition to a home entertainment product became a neat way for a kid (me) to “broadcast” to the neighbors.
About the same time, FM started to catch on as a superior means of delivering high fidelity to listeners. My first FM transmitter was constructed from plans in Radio-Electronics and I spent $5.00 in 1960s $$ on a single Philco 2N499 transistor to make it work. It did.
Third opinion is that a clean and reliable FM transmitter is much more difficult for the hobbyist to build from scratch. For reasons I can only guess the part 15 rules specified measurements which are beyond the capability of the hobbyist perhaps because it was not anticipated that this would be a do it yourself endeavor but rather would be dependent on commercial producers of transmitters. Surprisingly to me I know of no commercial units offered for sale from the 1950s until about the mid 1980s other than the toy “Mr. Microphone” which probably would not pass certification. Anyone know if it did?. Now we have the utility units which are used couple to car radios for MP3 uses. We also have kits and assembled certified units available. I maintain that FM transmitter construction is not a do it yourself activity and folks should take your advice seriously when you recommend using a certified FM transmitter.
Few hobbyists can measure the output of their transmitters accurately even in the 10’s of milliwatt range but the point is, and I shout for emphasis: THE LEGALITY OF FM TRANSMITTERS IS NOT DETERMINED BY WATTS!!!” so the measurement is meaningless. The best thought I can give to hobbyists such as you and I is to follow your advice and purchase a certified transmitter and if you use a kit then do what you need to to limit the range to about 200 feet.
The folks who try to achieve miles of range are the ones who cause and get into trouble. We all need to realize that community broadcasting beyond a few neighbors cannot be done within the rules.