The Public Safety Communications Council (PSCC) has advised the PSHSB that, effective February 6, 2912 and for a period of no longer than 90 calendar days, the four public safety coordinators that constitute the PSCC will not coordinate TDMA (7K60) fixed facilities in the VHF band at more than 10 watts ERP. This action is in response to reports of harmful interference to existing systems from TDMA VHF stations.
The letter says that the PSCC is working with a predominant manufacturer(think Motorola) of these systems to identify the problem, but that testing has not been conclusive. The PSCC now has asked TIA to test “all currently available TDMA hardware operating in the VHF band to assess their impact on existing equipment. A copy of the PSCC letter is available by clicking here.
For what it's worth, no such problems have been reported with analog, NXDN (think ICOM and Kenwood), or P25. If you are unfamiliar with the term "ERP", it is the total Effective Radiated Power that can be transmitted from the antenna of a mobile, base station, or repeater. This is calculated by taking the output power of the radio transmitter, deducting line loss and duplexer (if applicable) loss, and adding the gain of the station antenna. Typical ERP for VHF stations ranges from 150 to 300 watts.
