The Model 43 THRULINE® Directional Wattmeter accurately measures forward or reflected power in coaxial transmission lines under any load condition. Each Model 43 consists of a line section, ”QC“ (Quick Change) connectors and an indication meter housed in a rugged, corrosion-resistant aluminum case. The line section is a high-precision 50-ohm coaxial air line that inserts between the transmitter and the antenna or load. A socket is provided in each line section for a plug-in element with the desired power rating and frequency range. Line section ends are equipped with ”QC“-type connectors. The Model 43 is supplied with two female ”N“-type ”QC“ connectors. These con- nectors can be interchanged in the field without affecting instrument calibration. The instrument’s indicating meter is a shock-mounted 30-microampere meter with scales of 25, 50, and 100; permitting full-scale direct-power reading from 100 milli- watts to 10,000 watts. Plug-in elements determine the power rating and the frequency range, and these values are marked on each element. The elements rotate to read both forward and reflected power. There is no need for calibration charts or instrument adjustments. Elements can be purchased at any time and replaced in the field. For added conve- nience, Model 43 connectors and elements are interchangeable with many other Bird wattmeters. Remote installation can easily be achieved by removing the Model 43‘s RF line section and inserting it at any desired point in the line. For best visibility, the meter itself can be relocated using the 32-inch meter cable supplied in the instrument housing. Additional meter cable lengths can be ordered separately.