A bridged-T impedance bridge for the v.h.f. waveband

The paper describes three simple impedance bridges for frequencies of the order 50¿100 Mc/s. These bridges measure the unknown impedance direct in the form R + jX, where R is its resistance, and X its reactance. The use of a bridged-T network has enabled the stray admittances to be treated readily. This treatment has been further facilitated in the design by the fact that the impedance standards are all connected in parallel. Two of the bridges described are suitable for the measurement of the ¿direct¿ impedance between the two live terminals of a 3-terminal network. They possess the additional advantage that no input or output transformers are required in their construction. The third bridge is suitable for the measurement of impedances which are balanced to earth.