Bird Wattmeter Thruline Model 43 with 3 Slug Elements - 10C, 10E, 100D

Bird’s Model 43 Thruline wattmeter is a portable, insertion‑type directional RF wattmeter that uses plug‑in elements (“slugs”) to set frequency band and full‑scale power, and your 10C, 10E, and 100D combination gives a well‑curated HF–VHF coverage at low to medium power levels for service and bench work.testequipmenthq+1​

Model 43 key points

• General‑purpose 50 Ω RF wattmeter covering roughly 450 kHz to 2.7 GHz when used with appropriate elements, with typical full‑scale accuracy of about ±5% for CW power.testequipmenthq​

• Measures forward or reflected power depending on slug orientation (arrow toward load for forward, toward source for reflected), using an internal 50 Ω air‑line section and a rectifying element.birdrf+1​

• Rugged die‑cast metal housing with rubber bumpers, carrying strap, and “QC” (quick‑change) RF connectors; many units are fitted with N‑type or UHF connectors, which is worth stating explicitly in your listing.birdrf+1​

About the plug‑in elements

Bird’s plug‑in elements are band‑ and range‑specific, and buyers care a lot about exact code and condition.birdrf​

• 10C element

  • Nominal full‑scale power: 10 W.

  • “C” family typically sits in a VHF band block (e.g., tens of MHz to low hundreds, check the exact stamping and list it verbatim), so this slug is attractive for low‑power VHF service, exciter testing, and driver stages.birdrf​

• 10E element

  • Nominal full‑scale power: 10 W.

  • “E” family elements are a higher‑frequency band than “C” (again, the exact MHz range is stamped on the face, and you should quote that directly in your product copy), making it useful for higher‑VHF/UHF low‑power measurements.repeater-builder+1​

• 100D element

  • Nominal full‑scale power: 100 W.

  • “D” family is a mid‑band slug range; a 100D is commonly used for 50–100 W class HF/VHF transmitters and repeaters, making your bundle practical for typical ham and LMR service work.repeater-builder+1​

Because Bird has produced many element families and revisions over decades, and because region and age affect the exact MHz mapping of C/D/E codes, anyone selling a specific set should:

• Read and quote the full face marking for each element (e.g., “10W, 2–30 MHz, Element 10A” pattern) in the listing, rather than relying only on the shorthand codes.birdrf​

• Include clear photos of the front of each slug so buyers can verify the exact band and range against their own charts.repeater-builder​

E‑E‑A‑T‑style notes for your listing

To present this with strong expertise and trust:

• State the instrument’s role: “Directional 50 Ω RF wattmeter for forward/reflected power measurement using Bird plug‑in elements, widely regarded as an industry standard in RF service and field work.”youtube​testequipmenthq​

• Specify: connector type (N vs UHF), cosmetic condition, meter movement behavior (smooth, returns to zero, no sticking), and whether it has been recently checked against a known reference.file.yizimg+1​

• For each element, list: exact markings, nominal power rating, and printed frequency range, and note if the elements seat firmly and index correctly in both forward and reverse positions.birdrf​

For authoritativeness and trustworthiness, it helps to:

• Reference that Model 43 accuracy is specified as about ±5% of full scale when used with the correct element and a good 50 Ω system, and that it is intended for CW or average‑reading power, not true peak‑envelope power unless upgraded with a peak kit.testequipmenthq+1​

• Acknowledge limits: the wattmeter assumes a 50 Ω system; significant mismatch increases uncertainty, and absolute accuracy at the very bottom of the scale is inherently poorer than near full scale.file.yizimg+1​

Clear limits and caveats

• The Model 43 by itself does not define frequency or power range; these are entirely determined by the installed element. Your three slugs give specific coverage “windows,” not continuous 0.45–2700 MHz coverage.testequipmenthq+1​

• Accuracy claims rely on properly calibrated meter movement and elements; surplus units should be described as “not recently calibrated / sold as‑is” unless they have documented calibration.file.yizimg​

• This style of wattmeter is designed for 50 Ω coaxial systems; use on 75 Ω or other impedances is possible but introduces systematic error that the buyer must understand and accept.file.yizimg​

If you want, a next step is to draft a compact, product‑page‑ready description that quotes the exact text from each element’s face and your meter’s connector type and condition.