MDAR ANTENNAS 



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2). Current oscillating in the dipole generates electromagnetic waves 

 which travel out with the velocity of light. A single dipole is fairly 

 non-directive and consecjuently produces a relatively weak, field at 

 a distance. When the wave-length is short the field of a dipole in a 



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o o 

 Fig. 2 — A Microwave Dipole. 



Fig. 3 — x\ Dipole Fed Paraboloid. 



chosen direction can be increased many times by introducing a re- 

 flector which directs or 'focusses' the energy. 



In communication antennas the focussing reflector is most com- 

 monly a reflecting wire array. Even at an early date in radar the wave- 

 length was so short that 'optical' reflectors could be used. These were 



