The FCC prohibits unlicensed uses of the airwaves, partly to enforce a small group’s version of morality but largely to make sure the airwaves don’t degenerate into random noise and Clear Channel broadcasts. They do this by slicing up the full spectrum into bands, and allocating those bands to specific uses. It is illegal to use a band for anything other than its allocated purpose. This makes sense in dense regions, where pretty much every available frequency is in use by someone. Out here, on the other hand, most of the dial is completely empty (AM, FM, analog TV, and so on are all mostly quiet) and could be used for anything at all if you didn’t fear the FCC party-vanning you and your gear.
How come the FCC doesn’t allow non-interfering uses of bands that would otherwise go unused in a given area? This is (technically) orthogonal to the concept of licensing: The license could cover the mere usage of a broadcast rig on any frequency and allow such usage as long as the Prime Directive (the principle of non-interference) was strictly adhered to.
They do.
There’s a band called ISM (industrial, scientific, medical) which is unlicensed and allows pretty much any type of operation (within the power restrictions). The hitch is that you must accept interference from any other device. There are all sorts of wireless devices operating in this band.
Derleth asks why other bands can’t be used by non-interfering transmitters, not why there isn’t a band like ISM, right?
I would guess the reason is that it would be impractical to announce that non-interfering use is allowed, and then spend lots of resources settling arguments about what constitutes interference and who has to stop doing what.
Interference can take a lot of resources to track down. People driving around making measurements, almost finding the source but then it turns off, etc etc.
Also, HAMs will no doubt agree that it is possible to transmit properly in an allowed band, and still get complaints from neighbors, for example because the neighbor’s television set is too sensitive to what it should be seeing as out-of-(TV)band noninterference.
The more transmitters there are, the more work this all entails.
There’s another practical side. If it’s legal to use, say, a wireless thermometer in Montana that transmits within the FM Broadcast band, when a consumer in Montana moves to New Jersey and hangs their thermometer up, trouble ensues. So, no doubt the FCC would cringe at the idea of mass-produced products whose proper use requires the user make a judgement about the potential for interference.
I’ll add that some portions of the Ham radio allocations are shared. Particularly the 70CM band where the Hams are secondary users in some areas of the USA. In the HF section, ITU Region 1 SW broadcasters populate the lower parts of some bands. But since they use AM and we use sideband it’s not a problem.
Your cite is somewhat lacking: very few of those complaints were upheld. Just because they complain a lot doesn’t mean that the complaints are given any credence. For instace, this site says
The WSJ article requires a subscription.
For instance, the FCC obscenity site says they only took action in 12 cases in 2004, despite 1.4M complaints.
And in 2005, none of the 233K complaints were upheld.
From my experience with the ISM band, not only do you have to accept any interference but have to register the range (modulation?) when you apply for the liscense. Violations come with considerable fines. Even so, with the frequency and range set within limitations on the radios at our parent plant, we still get signal on our maintenance crew’s radios when they come to my warehouse 1.7 miles away (dense inner city and industrial environment with a major interstate running through the middle).
Perhaps the FCC limits use of non-specified bands in rural areas because, no matter how tight the regulations or how dedicated the effort to conform to these regulations, sometimes signals pass through and could wind up in an area where that band is assigned.
Just a theory based on limited experience though, I could be quite wrong.
Just because you think that you aren’t interfering with anyone, doesn’t make it so. Not hearing anything on a specific frequency with a particular receiver and antenna does not guarantee that you can transmit on that frequency without causing interference.
Bingo. The harmonics of your signal could interfere with transmitters on certain other frequencies; your signal and someone else’s might combine in a third party’s receiver (intermodulation) and make that frequency unusable. Problems like this are why UHV TV channel assignments were so scattered - in any given area just a handful of channels could be used without causing interference on other channels.