50, 150, and 450 MHz system performance in a Colorado rocky mountain county

This paper presents the technical approach and results obtained in attempting to resolve the land mobile communications problems for a 1000 square mile mountainous county of Boulder in Colorado. The project was broken into three phases: (1) Planning and Prediction, (2) Measurements, and (3) Recommendations. In the planning and prediction phase a map study of Boulder county was made to determine the terrain characteristics and to identify potential base, repeater, and relay station sites. Line of sight path loss calculations were made of the extent of coverage of these sites assuming operation on 40, 160, and 420/MHz bands. The measurement phase was conducted by establishing at each of the four selected sites a receiver and strip chart recorder combination on each of the three bands considered in the planning stage. A transmitter vehicle, simultaneously transmitting on 41 MHz at 100 watts, 162 MHz at 60 watts, and 416 MHz at 30 watts with a 1 KHz tone at 4 KHz deviation, was then driven over 130 miles of both flat land and steep canyon road. The strip chart recorder recorded both signal level and audio received. Throughout the measurements, unity gain antennas and high sensitivity, less than 0.2 µv for 12 dB SINAD receivers were used.