RADIO COMMUNICATIONS 



In addition to being sister ships structurally the Modoc and the 

 Mojave were equipped with identical radio apparatus for the ice- 

 patrol work. Each vessel had one T-2 2-kilowatt tube transmitter, 

 using either CW, ICW, or phone transmission; one T-4 200-watt tube 

 transmitter using either CW or ICW, which replaced the 2-kilowatt 

 spark set used during 1927; and a 500-watt XA crystal control high- 

 frequency transmitter. The latter was similar to the one used during 

 1927 with some improvements and redesigning of the circuits used. 

 The alterations were made by the United States Naval Research 

 Laboratory for the Coast Guard, and served to make the set more 

 efficient and consistent than before. 



Direct communication with NAA, the United States naval radio 

 station near Washington, D. C, was more successful than in any pre- 

 vious year. This traffic was all handled on high frequencies and the 

 average distance between the ship and the shore station was approxi- 

 mately 1,350 sea miles. 



The receiving apparatus on each ship consisted of a CGR-5 low- 

 frequency receiver used for ship traffic and for communication with 

 shore stations on intermicdiate and low frequencies. An RG receiver 

 was used for high-frequency work, covering from 1,000 to 20,000 

 kilocycles. No real trouble was experienced with any of the radio 

 apparatus. Kolster radio com.passes were used to assist the vessels 

 to find each other at relieving times. They would have been invalu- 

 able, also, had any assistance work been necessary during the season. 



A splendid spirit of cooperation was noted on the part of the ship 

 and shore stations in the vicinity of the patrol regions. There was 

 an increase of over 17 per cent in the number of water-temperature 

 and weather reports received from passing vessels over the 1927 

 season. A regular annual increase in all traffic seems to be the rule. 

 An idea of the present volume can be gained by reading the tabulation 

 on page 38 at the end of the summary report of the commander, 

 international ice patrol. 



The following schedule shows the times when regular routine traffic 

 was handled. The times given are all Greenwich mean civil times 

 and show the conditions at the beginning of the season. A few 

 minor changes were made in the schedules with NBD, Bar Harbor, 

 Me., during the progress of the patrol: 



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