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The United States Lines' 15 690-ton commercial-container ship, "American Alliance," was selected as lead ship for an onboard EMI survey prior to installation of 1535-1645-MHz (L-Band) shipboard terminals for communication via a maritime satellite. Three maritime communications satellites are currently in orbit: Marisat-1, over the Atlantic Ocean at 15Â° W. longitude, Marisat-B, over the Pacific Ocean at 176.5 E. longitude, and Marisat-C, over the Indian Ocean at 73Â° E. longitude. In general, the EMI survery revealed tolerable interference levels onboard ship: radiometer measurements indicate antenna-noise temperatures less than 70 K, at elevation angles of 5Â° and greater, at 1559 MHz, at the output terminals of the 1.2-m diametci, parabolic-dish antenna for the L-band shipboard terminal. Other EMI measurements include field intensity from 3-cm and 10-cm wavelength pulse radars, and conducted-emission tests of primary power lines to both onboard radars. This information should be helpful to designers of maritune L-band shipboard terminals.