We have 4 pair of channels (8 channels total) that are banned at our field due to outside interference. In our case, all of them are due to pager systems.

The FCC licenses pagers to operate between our RC channels. Most of the time, they aren't a problem, but if their transmitter is close by your field, or they have a really powerful transmitter, you'll get hits when they transmit.

And the fun thing about pager systems is that they are "off" most of the time, so you can fly and fly and fly and then suddenly get blasted with no warning.

The FCC does provide an on-line search system here:
http://wireless2.fcc.gov/UlsApp/UlsS...Geographic.jsp

Just pop in your field's location and a frequency range you're interested in. Remember to not look directly on your RC frequency, you won't find anything. Instead, look for a range around it. So if I'm looking for interfernece on channel 12, that's 72.030mhz. I'll put in a range of 72.010 through 72.050. That will pick up anyone licensed near channel 12.