| Chicago Burlington & Quincy Railroad SW1200 9273 at Chicago, Illinois on February 24, 1968, photograph by The Garys, print by J. M. Gruber, Chuck Zeiler collection. Number 9273 was built September 1955 ( c/n 20545 ), became BN 231, and later BNSF 3503. This shows what was known as a wagon wheel radio antenna, specifically, a Bendix Type MS-101A pre-tuned ground plane antenna connected to the MRT-1A communication unit powered by a MP-44A dynamotor power supply ( located behind the rear exhaust stack ). The dynamotor converted the locomotive's DC power to regulated power ( 13 volts DC tube filament and 325 volts DC plate voltage ) for the MRT-1A. |