Controlled coverage by co-channel transmission

Laboratory measurements are presented which indicate the following conditions should be met when operating co-channel base stations: 1. Carriers should be held to an off-set frequency that does not vary more than approximately 100 cps. 2. Carrier offset should be either held as close to zero as is practical, or to some mid-audio frequency value so that the beat frequency and its harmonics can be attenuated with notch filters. 3. The signal level in the interference zone should be above a critical value that depends on limiter design. 4. Modulation levels should be equalized. 5. The distance between base stations should be kept less than 25 miles.