Bird 43 Thruline RF Directional Wattmeter 50 Ohm w/ 5W 10W 2500W Elements N-Type

Bird 43 Thruline RF Directional Wattmeter 50 Ohm w/ 5W 10W 2500W Elements N-Type

The Bird Electronic Model 43 Thruline is one of the most recognized RF directional wattmeters ever made — a rugged, portable instrument used to measure forward and reflected RF power in transmission lines. It operates on the directional coupler principle: a plug-in element (slug) inserted into the meter body samples the RF field passing through, producing a reading on the large analog meter face. Swapping elements changes both the power range and the usable frequency range, making the Model 43 an extremely versatile instrument across a wide span of RF applications. This unit includes three plug-in elements as described by the seller (5W, 10W, and 2500W); please see the condition notes and photos for element details.

Specifications & What's Included

• Manufacturer: Bird Electronic Corporation, Cleveland, Ohio USA
• Model: 43 (Thruline RF Directional Wattmeter)
• Impedance: 50 Ohms
• Connector type: N-Type (female, both ports)
• Measurement: Forward and reflected RF power (directional)
• Power range: Determined by installed plug-in element
• Frequency range: Determined by installed plug-in element
• Included Element 1: 5W, 25–60 MHz (visible in left side slot in photos)
• Included Element 2: 10W (per seller listing — confirm element set upon receipt)
• Included Element 3: 2500W, 100–250 MHz, Peak Power (P2500C, visible in front slot in photos)
• Note: Photos also show a 100W 50–125 MHz element in the right side slot — buyers should verify exact element set; see condition notes
• Meter face: Dual-scale analog (part number 2060-002, per label)
• Form factor: Portable handheld/bench instrument with carry handle
• Housing: Gray cast metal, rugged field-use construction
• Calibration sticker: Certified Calibration Laboratories Inc., Philadelphia PA — dated 11-27-78 (repaired and calibrated); calibration not current

Applications

The Bird Model 43 Thruline has been in continuous production since the early 1950s and remains the de facto standard directional wattmeter in amateur radio, commercial broadcasting, land mobile radio, military communications, and RF laboratory work. Its plug-in element system lets a single meter body cover power levels from milliwatts to tens of kilowatts and frequencies from below 1 MHz into the UHF range, simply by swapping the appropriate slug. In commercial and government settings, the Model 43 is routinely used to tune transmitters, verify power output at antenna feedpoints, measure VSWR indirectly through forward/reflected power ratios, and commission new RF installations. It is equally at home on a ham radio operator's bench, at a broadcast transmitter site, or in a military communications van. The instrument's all-passive, no-battery-required design means it reads whenever RF power is flowing through the line — there is nothing to power up or calibrate beyond the elements themselves. The 2500W element included here covers the 100–250 MHz range, making it well suited for VHF FM broadcast, land mobile, and related high-power applications. The 5W element covers the 25–60 MHz range, useful for low-power HF/VHF work. The Bird 43 remains a highly sought piece of test equipment on the used market, and examples in good working order with quality elements command strong resale value.