The AN/MRN-1 was an instrument approach localizer used by the Army Air Force during and after World War II. It was standardized on 3 July 1942 replacing the SCR-241, and was a component of SCS-51. In accordance with the Joint Electronics Type Designation System (JETDS), the "AN/MRN-1" designation represents the first design of an Army-Navy electronic device for ground mobile radio navigational aid. The JETDS system also now is used to name all Department of Defense electronic systems.
Use The transmitter provided a signal to guide the RC-103 equipped aircraft to the centerline of a runway. The set radiates two intersecting field patterns, one of which is modulated at an audio frequency of 90 cycles per second, and the other at an audio frequency of 150 cycles per second. The shape of the radiated patterns were such that they intersected in a vertical plane called the "course", which could be oriented (by positioning the truck) to intersect the ground in a line which coincides with the center-line of a landing runway. The range of the equipment was a function of the elevation of the receiving antenna: approximately 40 mi (64 km) at an elevation of 2,500 ft (760 m), 70 mi (110 km) at 6,000 ft (1,800 m), and 100 mi (160 km) at 10,000 ft (3,000 m). The transmitter, BC-751-A had a frequency range from 108.3 to 110.3 MHz (277 to 272 cm) with a power output of 25 Watts.
AN/CRN-3 was the same equipment except without the K-53 truck, thereby making it air transportable, components were housed in a tent.
Components The AN/MRN-1 was mounted in a K-53 truck and was made up of the following components.
BC-915 control box BC-751 radio transmitter BC-752 modulator and bridge BC-753 course detector fixed BC-754 course detector portable BC-755 field intensity meter BC-777 indicator (alarm) RC-109 antenna (5 alford loops in a horizontal plane) An SCR-610 was provided for ground communications Electrical power was provided by a PE-141 generator (115 volts)
Aircraft components The RC-103-A was an airborne localizer receiver used to indicate a landing course in conjunction with the AAF instrument approach system. Signals received from a transmitter, located at one end of the runway to be used, are fed into the cross-pointer indicator indicating "on course", "fly right" or "fly left". Audio indication was also provided.
Antenna system AS-27/ARN-5 was used with the dual installation of the localizer and glide path receivers. Antenna type AN-100 was used when only the localizer receiver was also installed in the aircraft. RC-103 components included: Indicator I-101-C BC-732 control box BC-733 receiver with DM-53 dynamotor AN-100 antenna (localizer only) AS-27/ARN-5 antenna system (combination)
See also
AN/MRN-3 Instrument landing system List of military electronics of the United States List of U.S. Signal Corps vehicles LORAN Radio navigation SCR-277 SHORAN Signal Corps Radio
References TM 11-227 Signal Communication Directory. Dated 10 April 1944. TM 11-487 Electrical Communication systems Equipment. Dated 2 October 1944. Graphic Survey of Radio and Radar Equipment Used by the Army Airforce. Section 3, Radio Navigation Equipment. Dated May 1945. TO 30-100F-1. Dated 1943.
Further reading Erik M. Conway (2006). Blind Landings: Low-Visibility Operations in American Aviation, 1918–1958. JHU Press. p. 108. ISBN 978-0-8018-8449-8.
External links Exterior image T.O. 30-100F-1 1943 Designation-Systems.net - JETDS SCS-51 NASM antenna systems JProc.ca - Argus BC-733