At 11:23 AM -0700 10/21/07, Dale Kelly wrote:
John W. responded to Craig:Wireless mics are licensed, so you start off from an absurd point of view. No need to read further.In addition, each broadcast market, or geographic area, has a local frequency coordinator. This is often a Society of Broadcast Engineers (SBE) function and is sanctioned by the FCC. Licensed users of the broadcast auxiliary services (BAS), Satellite uplinks and vacant TV channel RF devices, such as wireless mics, must obtain specific frequency usage authorization thru coordination. Without this oversight it would be RF chaos, particularly in the major markets.
Thanks for the info about the frequency coordinators Dale. I was not aware that wireless Mics require licensing, although the info I am finding on the web suggests that the FCC does not enforce the licensing requirement.
As I suspected, there is no licensing requirement for medical telemetry devices that share the broadcast spectrum, however, the devices must be approved under the rules for their use, and they must be registered with the local frequency coordinator:
From http://wireless.fcc.gov/services/index.htm?job=licensing&id=wireless_medical_telemetry
LicensingWMTS operators do not have to apply for licenses from the FCC. In order to be authorized under the FCC's rules, a WMTS operator is required only to use equipment that is properly authorized under the rules and to register with the designated frequency coordinator.
This all makes sense, and given traditional practices I can understand why broadcasters are concerned about the potential for interference. It is also clear that there are many instances of unauthorized use of devices that share broadcast spectrum; wireless microphones are a frequently cited example. Many small shops use wireless mics and may use their gear in multiple markets. I can see where registration and coordination could get very bothersome and wonder what percentage of users actually work with local frequency coordinators.
For what it is worth, the rules for Medical telemetry devices are written in a manner that suggests that interference with broadcasters is not the real issue. The rules state that these devices are not protected from interference by licensed users. So I suspect that in the real world, people find a frequency that works, perhaps with the assist of a local TV guide.
There were numerous hits about problems with Medical Telemetry devices in the 1998 time frame when new DTV transmitters were being turned on; the FDA issued a warning to users about the new DTV stations in 1998.
This suggests that these devices are installed, using an available frequency that is not being used by local stations. If a new station uses that frequency it can cause problems for the telemetry devices, and indeed it did in a few markets in 1998.
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