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Tube-Era Radios and Radio-Related Equipment

Clough Brengle Model ZM-11/U


The ZM-11/U was the U.S. Navy version of the model 712 capacitance/resistance and turns-ratio bridge by Clough Brengle. A very compact unit designed for aircraft and shipboard use, the ZM-11 was nevertheless quite accurate. While most service grade bridges of the late 1950's only sported accuracies in the plus/minus 20% range, the ZM-11 was designed to achieve accuracies of around 5 to 10% or better. Given that the laboratory grade General Radio model 650-A impedance bridge would hold around 2 to 5%, the ZM-11 was a very respectable performer.

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