CJTF 7 upon the request of CTG 7.1. This silence consisted of 5 min, from H-3 to H+2 min; and was enforced for the protection of scientific equipment and data during all events. In addition, a daily radio silence period was established at 100M and 1500M for the scheduled daily dry runs. The dry rua schedule was not always consistent with the above mentioned plan; therefore, the requirement for daily radio silence was deleted during the middle of the operation. The greatest’problem that developed during the entire operation was that of interference to the diagnostic telemetering projects sponsored by UCRL and Project 34.1 (Sandia). Project 34.1 experienced serious interfer- ence by local radar radiation originating primarily from the U.S. Naval ves- sels present. JTF 7 directed TG 7.3 to observe complete radar silence on all vessels while at anchor in port. Close coordination between the respective TG communications officers was required in order to eliminate the electronic interference. The installation of a 600 automatic dial telephone system by CTG 7.5 on Elmer with integration of the Fred system provided excellent telephone service at Eniwetok Atoil. The Eniwetok-Hawaii-Conus Radio Phone Circuit was considered satisfactory and a great improvement over the Redwing operation. The installation of the TROPO system by CTG 7.5 between Eniwetok and Bikini was a great improvement. This system provided adequate voice telephone lines, hot lines, ciphony, and count-down requirements to this Task Group. CJTF SEVEN provided CTG 7.1 one ciphony channel, which was maintained and operated by NSA trained enlisted personnel assigned to CTG 7.5. The KY-5 equipment selected was cleared for Secret RD. It provided excellent service and is recommended for future operations. Approximately 135 frequencies were assigned to TG 7.1 for scientific use. Early assignments of the frequencies is highly desirable in order that participating activities can advise their respective contractors to purchase the required equipment. Task Unit 5 (EG&G) provided the voice count~down broadcasts over 153.89 and 243.0 Mc for all elements of the Task Force. The voice countdown broadcast was capable of patching into the major nets, thereby reducing the requirement for additional voice count-down receivers. This proved to be very beneficial to all the Task Units and projects concerned. The CJTF 7 originally ruled that additional amateur radio stations would not be authorized because of the five stations permanently operating in the EPG. However, during the middle of the operation this order was rescinded, thereby opening the door to all task units. Four additional stations were finally authorized by CJTF 7. The procedures for obtaining call signs and licenses from the High Commissioner of the Trust Territory conflicted on several occasions and created a large volume of unnecessary correspondence. The additional amateur radio stations were of great morale value and did not cause any interference problems. The success of communications provided during operation Hardtack can in part be attributed to the frequent communications conferences between Task Force Communications Officers during the interim and build-up period. These conferences are deemed necessary in order to obtain close coordination and a working agreement between the respective Task Groups. Communications at Johnston Island. 104 Radio communications during News-