each Responder station as a digital readout at the Interrogator. In this manner 

 positional ambiguities are eliminated when the position is initially known to with- 

 in 10, 000 meters. 



a. Modes of Operation 



Two basic modes of ranging operation are available. In the Automatic 

 trigger mode, the Autotape Interrogator utilizes a built-in program to measure 

 the range to each Responder and display it automatically. A nonambiguous range 

 is displayed on each of two digital readouts once each second. In the Fine, Inter- 

 mediate, or Coarse method of operation, the ranges will be measured and dis- 

 played at a rate of three times each second. At this high rate of operation, only 

 the last three digits of each range measured are presented: 



(1) Fine =^ to 100 meters with 10-cm resolution. 



(2) Intermediate = to 1000 meters with 1 meter resolution. 



(3) Coarse = to 10, 000 meters with 10 meter resolution. 



In the External mode of operation cycling times of less than one per 

 second are under the control of the operator. A Hold position is also available 

 where the display is locked to its last reading. Each of these modes has specific 

 applications dependent upon the conditions of operation. 



b. Antenna Requirements 



To provide flexibility of operation in the selection of range and area of 

 coverage both an omnidirectional antenna and a 60° beam horizontal horn have 

 been designed for use with the Autotape equipment. Operational ranges of 25 - 

 100 km are predicted when these antennae are used in proper combination at the 

 Interrogator and Responder stations . 



An rf unit is mounted integral with the antenna, making it possible to 

 position the antenna assembly away from the Interrogator or Responder by in- 

 creasing the length of the connecting cables. Equipment calibration does not 

 change with this arrangement. 



c . Operation 



All range measurements are initiated from the Interrogator unit after 

 the Interrogator and Responder close the radio link using the Talk Mode of oper- 

 ation. The operator at the Responder then tunes to receive the Interrogator 



145 



arthur ai.lLittlcilnr. 



