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A portable general purpose radio frequency absorption type wattmeter used to measure output power and to facilitate tuning of transmitters. It may be used as a dummy load of 51.5 ohms up to 60 watts, as a modulation monitor, as an accurate radio frequency resistance, and for loss measurements on transmission lines. Power indications are read directly on a double scale dc microammeter in rf watts.

AN URM-43.png

Technical Description

Circuit Information
The circuit consists of a 50-ohm coaxial load resistor and a dual range crystal rectifier type voltmeter capacitively coupled to the load resistor. The dummy load-voltmeter housing is oil filled and surrounded by a finned radiator structure. A neoprene expansion -diaphragm, which prevents pressure rise with temperature, is mounted on the front of the housing.
Power Supply
Frequency Range
Wattmeter, 30 to 600 mc. Dummy load, 0 to above 900 mc. Power Range: 2 to 60 w in two ranges, 0 to 15 and 0 to 60 w
Type of Reception
CW, AM, FM, or TV type signals
Voltage Standing Wave Ratio
Less than 1:1
Output Impedance
51.5 ohms
±2% of full scale reading
Temperature Range
-40° C (-40° F) to +55° C (+131° F)
Major Unit
1 - AN/URM-43A 7" x 5" x 9"; 9 lbs

Tubes, Crystals, Transistors

  • 1 - JAN-1N82 (Crystal Rectifier)

Reference Data and Literature

NAVSHIPS 91842 (Instruction Book)
TO 33A1-7-9-11 (Instruction Book)