In-line wattmeter

  
The circuit is not frequency sensitive. Its calibration will be accurate over a wide frequency spectrum, such as the entire amateur hf spectrum, if the values of L2, the voltage divider capacitors Cl-2 and C3, and the resistances of Rl-2 are chosen properly. Rl-2 and CR1-2 should be matched for best results
In-line wattmeter - schematic

Generally, Rl-2 must be small compared to the reactance of L2 so as to avoid any significant effect on the L2 current which is induced by the transmission line current flowing through LI. The lower frequency limit of the bridge is set by the Rl-R2/Ls ratio, and the cutoff is at the point where the value of Rl-R2becomes significant with reference to the reactance of L2 at that frequency point.




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