UHF television interference associated with cellular mobile telephone systems

Abstract

An investigation is made into two types of interference which may occur between UHF television and 850 MHz cellular mobile telephone systems: 1) ITV--interference to the cellular mobile telephone receivers, created by a UHF TV transmitter; 2) TVI--interference to the UHF TV receiver, created by the cellular system mobile transmitters. In the case of ITV it has been determined that TV transmitters operating on TV channels 65 through 69 may produce third-order intermodulation, within a radius of about 0.5 mi, to certain telephone channels assigned to mobiles operating in a cellular system fringe area. A judicious choice of telephone channel assignments would mitigate this type of degradation. Alternatively, in the case of TVI, it is shown that within a minimum grade B television service area, it is possible for cellular mobile telephones to at times produce image interference to present-day UHF TV receivers tuned to channels 58 through 61. However, because of cellular telephone subscriber density and channel position (and loading) the probability of interference is expected to be low. An increase of TV receiver image rejection by 20 dB would essentially eliminate all likelihood of this interference.