RADIO COMMUNICATIONS 



In view of the fact that 1931 marked the first assignment of the 

 General Greene to a duty such as the International Ice Patrol, it is 

 deemed desirable in this report to give a description of the radio 

 apparatus carried and its operation. The special work necessitated 

 several changes in the ship's regular radio installation. When ready 

 to depart on ice-patrol duty the receiving equipment used consisted 

 of four separate units, namely: One CGR-25A intermediate fre- 

 quency receiver capable of covering a range from 75 to 1,000 kilo- 

 cycles; a CGR-27 low-frequency receiver similar in design to the 

 CGR-25A, but WTLth the exception that the frequency range was 

 from 15 to 120 kilocycles; a CGR-30 high-frequency receiver cover- 

 ing a range from 2,315 to 2,705 kilocycles; and a fourth unit con- 

 sisting of a CGR-18 radio direction finder and receiver. The change 

 from the CGR-IA high-frequency receiver to the more sensitive 

 CGR-30 receiver was made the day prior to leaving for ice patrol. 



The entire installation of receiving equipment performed remark- 

 ably weU throughout the whole ice-patrol season, the CGR-25A being 

 used on the commercial ship and shore frequencies, and the CGR-27 

 in obtaining news and weather reports. Of special interest was the 

 performance of the new screen-grid high-frequency receiver, the 

 CGR-30. It proved itself in every way to be superior to the older 

 type CGR-lA receiver which it replaced, in selectivity, ease of oper- 

 ation, and especially in its splendid performance. For instance, when 

 in north latitude 50° and northeast of Togo Island, telephone recep- 

 tion was had from both Base 20, Fernandina, Fla., and Base 21, St. 

 Petersburg, Fla., with ample volume for a loud speaker. This instance 

 is cited primarily for the fact that with the old type CGR-1 A receiver, 

 reception of telephone signals at that distance would have been 

 impossible. 



The transmitting apparatus installed on the General Greene con- 

 sisted of two units: The T-5 200 watt CW-ICW tube transmitter, 

 w^th a frequency range from 500 to 250 Idiocy cles, and the new T-6 

 transmitter covering a range from 2,307 to 3,333 kilocycles. The 

 T-5, used for ship-to-ship and ship-to-shore communication on com- 

 mercial frequencies, had been installed for some time, while the T-6 

 Coast Guard high-frequency transmitter was installed a few weeks 

 prior to leaving for ice patrol. This latter transmitter replaced the 

 T-lA installation, and was of the crystal-controlled master oscillator 

 power- amplifier type, with provisions made for the use of CW, ICW, 

 or telephone transmission. This particular transmitter performed 

 remarkably well, allowing the General Greene to keep in communication 



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