MICROWAVE REPEATER RESEARCH 



211 



to lump transmitting frequencies in one group and receiving frequencies in 

 another. When separate microwave shielded lens antennas are employed 

 for transmitting and receiving in each direction it becomes practical to use 

 a frequency plan in which transmitting and receiving frequencies are in- 

 terleaved. Such a plan eases filter requirements considerably and has 



ANTENNAS 



— e> 



1 RADIO-- ! 



j FREQUENCY 

 FILTERS ^■ 



4150 



4110 



4070 



} GUARD 

 4030 I) ACTIVE 



3910 |iaMC 

 20, MC 



3870 



3830 

 MC 



I —I 80 MC 



40'mC I 



LONG 

 -•-WAVEGUIDE 

 LINES 



<R 



FREQUENCY 

 PLAN 



REPEATER GAIN 



FILTERS MUST; 



SEPARATE OR COMBINE CHANNELS 

 WITH MINIMUM POWER LOSS. 



PROVIDE EXCELLENT IMPEDANCE 

 MATCH TO ANTENNA LINES 



DISCRIMINATION REQUIREMENTS: 



LESS IMPORTANT AT PRESENT 

 BECAUSE OF: 



ANTENNA DIRECTIVITY, 



l.F. DISCRIMINATION 



Fig. IV- 1. — Schematic diagram of a possible five channel radio repeater station. 



certain other advantages to be discussed in Section V. A possible re- 

 peater employing such a frequency scheme is illustrated schematically in 

 Fig. IV-1. 



If a radio frequency branching filter is to fit properly into a repeater it 

 must separate or combine channels without excessive loss of signal. In 

 addition it must provide an excellent match to the long line which leads 

 to the antenna, otherwise troublesome echoes in this line may be caused. 



