Abstract:
The desirable characteristics of the APO system are the high value of look and capture ran6e together with low value of noise bandtidth. These three are not compatable with each other i.e. the increase of the look and capture range of the system is accompanied with an increase rf noise bandwidth of the system. However, after the system is locked the noise bandwidth can be reduced without
affecting the other desirable characteristics. A two pos-ition servomechanism has been developed which incorporates this idea. Initially, the system starts with a broad band loop and after it has synchronised it automatically switc-hes over to a narrow band condition thereby, reducing the noise bandwidth. It has been shown theoritically and exE-erimentally that this switching action does not.introd-uce any instability.
