The Legend Lives On -- An RF Wattmeter For Power Measurements

By Lynn Strube, Bird

The evolution in public, military and emergency communication is growing at an explosive rate. This reality necessitates the essential need for transmitting equipment to function at its full potential. Confidence in the equipment means knowing that on the operating frequency, the power specified by the transmitter manufacturer, is being achieved, delivered to the antenna and being broadcasted. A Bird THRULINE® Wattmeter was the best selection in the past for measuring RF power and is still a trusted selection today.

The Bird THRULINE® Wattmeter model 43 was created, and first produced, in the 50’s. The selfcontained instrument used microwatts of energy from the transmission it measured. Its precision reference line section made it economical and provided build-in reference accuracy that remained consistent with age.

In the 1960’s the mobile radio had the majority of its components stored in the trunk of a car and was comparable in size to a microwave oven. A Bird 43 THRULINE® Wattmeter was used to test the power output of the two-way mobile radio transmitter and to match it to the antenna most commonly mounted on the trunk. The transmission line to the antenna was very short. This provided easy access to the equipment which in turn made measuring the equipment convenient. Additionally, the same wattmeter was used to measure the RF power in the operational base station.

In the 1970’s, the mobile radio had advanced from the trunk of the car to the car’s front interior. The Bird 43 was still used in the same capacity of testing the RF output and matching the transmitter to the antenna. However, the new interior position of the mobile radio, and the existing rear antenna position required a longer transition line. This still provided easy access to test and measure the system.