DESIGN OF SYSTEM — NORTH ATLANTIC LINK 



63 



20 



40 60 80 100 120 140 



LINE FREQUENCY IN KILOCYCLES PER SECOND 



160 



180 



Fig. 16 — System noise. 



completion of laying. The noise is lower than on the No. 1 cable. This is 

 because results of experience on the No. 1 cable were utilized in better 

 choice of cable repeater section lengths and in better equalization while 

 laying the 1956 cable. 



Modulation Tests 



Two-tone modulation tests of second and third order products were 

 made, using a large number of successive frequency combinations. The 

 highest level modulation products were at least 60 db below the 1 -milli- 

 watt test tones, at zero transmission level. This is approximately the 

 value computed before the system was laid. Most of the modulation 

 products were down substantially more than 60 db. Probably various 

 causes contributed to the good performance, including the effect of mis- 

 alignment in lowering repeater levels, and small propagation-time dif- 

 ferences which minimize in-phase addition of third-order products from 

 successive repeaters. 



Telegraph Transmission Tests 



At present writing, telegraph tests have been made only on the printer 

 (telegraph order wire) channels, and without a system multi-channel 



