frequencies with other services rmde the use of higher frequencies mandatory. Despite attempts to improve the system, it was found impr ossible to maintain a consistently high grade of service on the teletype channels although the voice channels were generally usable. The primary cause of the trouble was determined to be the large number of transmitters in operation aboard the USS ESTES, These, particularly when operating CWj introduced high-level pulses into the SSB receiver and caused intolerable garbling of the teletype channelso The same interference caused the back-up multiplex teletype to be completely unusable. Both of these systems operated successfully from the ship to ENIWETOK, despite relatively inefficient shipboard transmitting antennas, largely due to superior receiving”conditions at JAl?TAN. The conventional AM voice circuits planned as back-ups for the voice channels of the SSB system were not usable in either directim} both bemuse of the shipboard noise and interference and because the ship did not bve transmitters of adequate power; however, since the voice channels of the SSB system were generally usable, the back-up facilities were not required. (2) Multiplex radioteletype system to KWAJALEIN. In the past, this system had been oparated on sky-wave propagation using a variety of high frequencies with horizontal doublet antennas; results had been medicore. Installation of a ground-wave antenna system using two vertical radiating towers excited in phase on a fraquency in the 2 to 3 negacycle range, backed up by a two-wire terminated sloping dipole normally operated in the 3 to ~ negacycle range, raised the efficiency of this system to an acceptable levolo 75 — - — ~- — -- - - --- --- ----- ---