Gear Spotlight: The Bird Model 43 Wattmeter, New or Used on eBay

The Bird Model 43 is one of the best-known RF wattmeters around. Bird still sells it new, and used meters show up on eBay in large numbers, which makes it one of the most common ways an amplifier builder ends up with a professional-grade RF wattmeter on the bench.

What the Model 43 is

Bird lists the Model 43 with a frequency range of 2 MHz to 1.2 GHz, a power range of 100 mW to 5 kW and accuracy of ± 5% of full scale. It measures RF power with a passive, mechanical design built around a directional coupler and an analog meter movement. The nominal impedance is 50 ohm, and Bird's instruction book gives directivity greater than 25 dB.

The meter displays forward or reflected power depending on which way the plug-in element faces. Rotate the element and you measure power in the other direction, which is what makes it so useful for load matching and tuning. The ranges above describe the whole system: the element you install sets the band and power scale for any one reading.

Buying a used one

• Elements matter as much as the meter. A meter with no element, or only elements for the wrong band, will not read HF amplifier power. Check exactly which elements are included and what they are marked for.
• Check the connectors. Bird's datasheet lists the primary line as Bird QC, with N female normally supplied, so plan for good adapters if your station uses UHF connectors.
• Look at the meter movement. The needle should rest at zero, and Bird lists a manual zero-adjust screw for setting it. A sticking or bent needle is a repair job.
• Think about calibration. Bird recommends calibrating the Model 43 and its plug-in elements every 12 months. An older used meter may be well out of date, so treat its readings as approximate until it has been checked.

Using it safely

Bird's instruction book is direct about RF voltage: when working with RF powers of 200 watts or more, the potential of the center conductor of the line section will be over 100 volts, so do not touch the center conductor while RF power is on. Handle elements with care, because Bird warns that calibration could be disturbed if they are dropped. For low reflection measurements, Bird also cautions against rotating the reflected power element to read forward power, since damage to the element or wattmeter could result.

Know what it is built for, too. Bird says the Model 43 is intended for use with CW, AM, FM and TV modulation, but not pulse modulation, and that it is not suitable for accurately measuring digitally modulated signals such as DMR, TETRA or LTE. For amplifier tune-up, a steady carrier into a good dummy load gives the clearest readings.

Where it fits on the bench

In line between an amplifier and a dummy load, a Model 43 shows output power and reflected power at a glance, which is exactly what you need when adjusting a new build or checking a repaired one. Because it is passive, there is nothing to boot up and no batteries to replace.

And a reminder whenever amplifier power is discussed: external linear amplifiers are not legal for use on CB radio. A good wattmeter belongs in any licensed amateur station.

Educational reference only. Always verify all values independently against your specific device datasheet and build documentation. Working on RF and high-voltage equipment carries real risk.

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