New type of magnetic modulator using a single toroidal core

ELIMINATION of zero drift in magnetic modulators has taken two courses. The first involves using the second-harmonic flux components in two equally rated saturable-reactor elements which secure decoupling between a-c excitation windings and d-c signal windings.
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Since, in these twin-core modulators, the second-harmonic component of output voltage is generally selected by filtering and used for controlling a tuned a-c amplifier, the relatively high residual noise-output voltage, caused by slight core mismatch, places stringent requirements on both filter and amplifier circuits.