and maintain the equipment. During its yard availability period (31 October - 14 November 1953) the USS ESTES underwent a thorough communications and electronics check to determine the causes of the severe interference experienced during Operation IVY. As a result of this check, repairs were made and the equipment tested to deter= mine state of readiness, Although few HF facilities could be test- ed, all of the Combat Information Center (CIC) - Very High Frequency (VHF) equipment was checked and found to be operating satisfactcrily with substantial improvement in efficiency and reduced interference, In order that the communications personnel aboard the ESTES would be adequately prepared to assume their duties, one officer and ten enlisted men were placed on temporary additional duty (TAD) with the Army Task Group on Eniwetok. These men received approx- amately four weeks of on-the-job training in the Eniwetok communi~ cation, relay, ard crypto centers. Also, a number of the sommuni-+ cations personne. from the ESTES attended various electronics spe-— cialists schools to increase their technical proficiency. In addition to those deficiencies pointed up by Operation IVY, other factors had to be taken into account in CASTLE ccmmunication planning, One such factor arose when tre AEC announced the PPG would be extended to include Bikini Atoll for this expansion creat- ed a need for voice encoding equipment eiphory). The ciphony requirement was given to the NSA in February 1953 and in April 1953, NSA replied that HF ciphony was mot available at the time, but that experimental bread band VHF ciphony could possibly be made available.