The Bird Model 43 THRULINE® directional wattmeter is a portable insertion-type instrument for measuring forward and reflected power in coaxial transmission lines. It will accurately measure RF power under any load condition. Plug-in elements are available to fit your frequency and power needs. The more common ones are listed below.
The Bird Model 43 N is shown right with optional elements (sometimes called slugs). This model features N connectors for input and output.
The plug-in elements (slugs) determine the power rating and frequency range of the Bird 43 wattmeter. A few of the more common ones are listed below.
| Model: | Range: | Power: |
| 50H | 2- 30 MHz. | 50 Watts |
| 100H | 2- 30 MHz. | 100 Watts |
| 250H | 2- 30 MHz. | 250 Watts |
| 500H | 2- 30 MHz. | 500 Watts |
| 1000H | 2- 30 MHz. | 1000H |
| 5000H | 2- 30 MHz. | 5000 Watts |
| 10000H | 2- 30 MHz. | 10000 Watts |
| 500B | 50-125 MHz. | 500 Watts |
| 25C | 100-250 MHz. | 25 Watts |
| 50C | 100-250 MHz. | 50 Watts |
| 100C | 100-250 MHz. | 100 Watts |
| 5D | 200-500 MHz. | 5 Watts |
| 50D | 200-500 MHz. | 50 Watts |
| 50E | 400-1000 MHz | 50 Watts |
| 1000E | 400-1000 MHz. | 1000 Watts |
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