Chapter 7 — COMMUNICATIONS EQUIPMENT AND OPERATIONAL PROCEDURES 



FREOUENCY SHIFT CONVERTER 

 CV-483/URA-I7 



unit is not required. The physical size of the 

 AN/URA-17( ) is further reduced by using 

 transistors and printed circuit boards. The com- 

 plete equipment is less than half the size of the 

 older AN/URA-8( ). 



Proper tuning of the receivers feeding these 

 converters is important. Good communications 

 are often the result of a properly tuned receiver. 

 Each converter has a small oscilloscope mounted 

 in the front which supplies the operator with 

 a visual presentation of the input signal into 

 the converter. Refer to figure 7-16 for ex- 

 amples of how the correct scope presentation 

 should appear when the receiver has been properly 

 tuned. 



50.76 

 Figure 7-15. — Converter-Comparator Group AN/ 

 URA-17 ( ). 



station use. In frequency diversity operation, 

 the two receivers are tuned to different carrier 

 frequencies carrying identical intelligence. 



In diversity reception, the audio output of 

 each receiver is connected to its associated 

 frequency shift converter, which converts the 

 frequency shift characters into d.c. pulses. The 

 d.c. (or mark-space) pulses from each con- 

 verter are fed to the comparator. In the com- 

 parator, an automatic circuit compares the pulses 

 and selects the stronger mark and the stronger 

 space pulse for each character. The output of 

 the comparator is patched to the teletypewriter. 

 The converter units can also be used individually 

 with separate teletypewriters to copy two dif- j 

 ferent FSK signals. 



The newest converter-comparator group, the 

 AN/URA-17( ), is a completely transistorized 

 equipment designed to perform the same func- 

 tions as the AN/URA-8( ). Since present pro- 

 curement of frequency shift converters is confined 

 to the AN/URA-17( ), there are relatively few 

 installations having AN/URA-8( ) converters. 



The AN/URA-17( ) consists of two identical 

 converter units; each converter has its own com- 

 parator circuitry. Hence, a separate comparator 



CONUS METEOROLOGICAL 

 DATA SYSTEM 



(COM EDS) CIRCUITS 



The modern high performance aircraft used 

 in naval operations requires a myriad of nation- 

 wide and worldwide weather data to ensure 

 safety and mission completion. To meet these 

 requirements, circuits were being saturated with 

 data. In most cases the data routinely received 

 was only useful to a few weather offices. The 

 COMEDS System, a USAF managed component 

 of the Defense Communications System (DCS), 

 was designed to alleviate overloading of cir- 

 cuits and provide weather offices with the data 

 routinely required for the completion of their 

 mission and assigned tasks. 



COMEDS consists of nineteen area circuits 

 with 20 to 25 pieces of terminal equipment on 

 each circuit (fig. 7-17). It is a duplex system 

 (receive on one side and transmit on the other 

 side of the circuit) consisting of a 1200 wpm 

 loop circuit. The system is completely con- 

 trolled by a Univac 1108 computer at the Car swell 

 ADWS. It contains an error detection capability 

 advising you when an error occurs; you re- 

 ceive only that data specifically addressed to 

 you. Transmissions from various stations are 

 controlled by a polling sequence comparable to 

 the old COMET system. 



The system is engineered in a way that 

 most data delivered will be individually tailored 



137 



