Operation of close-spaced antennas in radio relay systems

The required attenuation between transmitter output and receiver input for any given pair of equipments may be measured by a method that takes into account both receiver desensitization caused by front end overloading and the interference effects of transmitter noise side bands. These are the two principal causes of degradation in receiver performance where simultaneous transmission and reception is to be accomplished from antennas to be placed in close proximity. With the required isolation known, curves may be consulted to determine the necessary antenna physical spacing, either colinear or in the same plane. The actual attenuation between two antennas including their associated transmission lines may be measured and, lastly, the presence of any receiver desensitization may be determined under practical operating conditions. A method for increasing the isolation between close-spaced vertical antennas for a given transmitter operating frequency is described.