802.11b Part 15 devices in and around the Amateur 2304 Band
There are thousands and thousands of FCC allocated Part 15 unlicensed devices operating within Amateur UHF and above bands. Do these cause problems now, will they in the future? Possibly you have already had experience with interference from these devices Most of them are Internet related and used to provide wireless broadband network connections with homes, businesses and even within an entire business or university campus.
Generally the technology is referred to as WAN or LAN. These are acronyms for wide area network and local area network. The names themselves are pretty descriptive aren't they? The chart below shows the various frequency "channels" used by these networks. Of course, these are only part of the problem since we also share spectrum in our 903 MHz and 5760 MHz bands. More on those bands as time permits me to put it together.
| Channel | Low Freq. | Center Freq. | High Freq. |
| 1 | 2401 | 2412 | 2423 |
| 2 | 2406 | 2417 | 2428 |
| 3 | 2411 | 2422 | 2433 |
| 4 | 2416 | 2427 | 2438 |
| 5 | 2421 | 2432 | 2443 |
| 6 | 2426 | 2437 | 2448 |
| 7 | 2431 | 2442 | 2453 |
| 8 | 2436 | 2447 | 2458 |
| 9 | 2441 | 2452 | 2463 |
| 10 | 2446 | 2457 | 2468 |
| 11 | 2451 | 2462 | 2473 |
All of these systems use spread spectrum, hence the very wide bands of operation. Now these signals generally do not travel that far, at least in residential applications, but none-the-less, they can cause extensive interference to Amateur Radio operation. Now FCC rules allow Part 15 unlicensed devices to use fixed sections of spectrum (and it always seems to be a Ham Band) but their rules spell out the conditions. Simply stated, it is up to the Part 15 user to solve any interference with a licensed service including shutting the system down if they are unable to solve interference issues. This gives us as Hams some baby teeth should we encounter interference from these devices. The problem we face, if harmful interference is experienced, is getting that done. A manufacturer designs and builds the product and sells it to a consumer (for example) who sets it up. Now this consumer knows nothing at all about part 15 rules and regulations. The manufacturer is now out of the loop so the user becomes our target if their equipment interferes with Amateur Radio. So how do you get your next door neighbor, or the local Starbucks, to turn off their (WAN or LAN) network so that you can make that satellite contact? In short, you don't. Short of a lengthy and painful lawsuit before a judge who may know nothing about FCC rules, you are sort of stuck. Figuring out the source of the interference may in itself be a problem.
So where do we go from here? I wish I had an answer! But as more and more of these devices populate our spectrum, there are going to be more and more problems. So if you hear what sounds like popping noise, you may have part 15 devices interfering with your equipment.