TD-2 MICROWAVE RADIO RELAY SYSTEM 



1045 



system having a capacity of hundreds of 4 kc message circuits. Alternately 

 each of these broad-band channels can be used to provide a 4-megacycle 

 video circuit of the kind required for present day black and white television 

 or they may be used to provide broader band television circuits if the need 

 for such circuits develops. The video or message input to a channel is fre- 

 quency modulated on a 70-megacycle carrier, translated up to the micro- 

 wave band, amplified and combined with the microwave output of other 

 channels in the same direction. The combined output is carried through a 

 single waveguide to a directive transmitting antenna^ beamed toward the 

 next station. At a repeater point the six-channel signal is received on a single 

 antenna, separated by means of channel separation networks, and each 

 channel converted to a 70-megacycle IF band for amplification. At a through 

 repeater point this 70-megacycle IF signal again modulates the 4000-mega- 



OHIO 



O RADIO AUX. STATION 

 ® RADIO MAIN STATION 

 (A) ALARM AND MAINTENANCE CENTER 

 MAINTENANCE CENTER 



PITTSBURGH 



Fig. 4— Typical TD-2 route section. 



cycle carrier, is ampHfied, added to the other channels in the same direction 

 and delivered to the transmitting antenna. These are the simplified func- 

 tions performed by the one-way radio repeater of the TD-2 System. 



In order to feed a standard video or a multi-channel carrier signal into a 

 TD-2 Radio System, an intermediate transmitter is required to frequency 

 modulate these signals around a center frequency of 70 megacycles. This 

 unit is known as the FM terminal transmitter. Likewise, at a receiving 

 point an intermediate receiver is required to convert the 70-megacycle 

 signal back to a video or carrier system signal. This unit is known as the 

 FM terminal receiver. 



A perspective of the system may be obtained from a typical route section 

 as shown in Fig. 4. A long system is broken into sections by means of main 

 repeater stations every few hundred miles. Auxiliary stations interconnect 



