- There aren't very many enforcement actions against AM operators, only around four or five each year.
- Enforcement actions centered on very high power operators and the configuration of the transmitter, antenna and ground wires with a focus on the "three meter rule."
- Unlike the actions against AMers, there are several actions each month against FMers so FMers are really getting lots of enforcement attention.
- It's all about the field strength in microvolts per meter, folks, so that's what we really need to discuss.
A transmitter with very low power output (in the microwatt range) could be matched with a very well constructed antenna and would probably violate the letter of the law. On the other hand, some certified FM transmitters have a rather high power output (perhaps 10 milliwats or 1/100th of a watt) but an intentionally poor antenna system to achieve the 250 uV/m rating. This is why FCC certified FM transmitters are usually certified as a complete unit including the antenna - and why changing anything on a certified FM transmitter voids the certification.
My survey of the 300 recent FM enforcement actions shows blatant disregard for the FCC limits (AKA "Pirate Radio" I guess) with field strength readings in the tens of thousands of uV/m at hundreds of meters away. I found only one action that seemed to be in the realm of useful for this discussion. The relevant portion is here:
The operation on frequency 107.7 MHz was measured at 1,381 microvolts per meter (uV/m) at 3 meters. This exceeds the allowable unlicensed limit of 250 uV/m at 3 meters established in Part 15.
So, at just a shade under six times the permitted field strength, we see an enforcement action. This was the lowest field strength enforced against in my review. But again, what does this really mean for a hobbyist? Transmitters are advertised to us with power output in watts, no one gives us field strength until we get busted! Here is what I have learned through experimentation and yes, I have been busted so I did get the field strength (more on that later).
I have connected a 10 mW (10 milliwats or 1/100th of a watt) transmitter to a well matched dipole and the absolute maximum range was 1000 meters using a car radio for reception that has a sensitivity of about 40 uV/m. What this tells me is that as long as you stay in the sub-watt power output area (10 mW, 100 mW, maybe even 1/2 watt with a not-very-good-antenna) you will likely fall below the enforcement threshold.
On the other hand, should you buy one of those FM blow torches off of ebay (2 watts, 5 watts and more), the number of enforcement actions in the FM band indicate you will likely be told to turn it off in a fairly short period of time. So, what's that like? My experience was that the quality of the enforcement experience is really up to you. As long as you are operating at a reasonable (even if not compliant) power level, not advocating sedition and are responsive to the FCC requests, the worst of the experience will be turning off your transmitter.
I received my NOUO back in 1997 so it's not online yet, but it looked just like the NOUO referenced above. My NOUO arrived by certified mail and I responded immediately. I shut down my transmitter and wrote back that the violation was inadvertent, that I was trying to adhere to Part 15 rules, that the transmitter was permanently off the air and that I would not violate FCC rules again in the future. I sent that letter certified mail as well and I received a very polite letter back thanking me for my cooperation and telling me that the matter was closed. Whew!
So for me the worst part was turning off my transmitter - it does hurt a bit to silence something we hobbyists tend to fall in love with. I think the message here is try to stay compliant no matter how frustrated you might be by the limited range because a silent transmitter has far less range than a compliant one!
That, and try AM whenever possible - more range, less enforcement - win/win!