RF Phase Shifters for Phasingtype SSB Rigs

Here are four popular methods to achieve quadrature (90°) phasing: X/4 transmission line, pi network, tee network and quadrature hybrid. Learn about their strengths and weaknesses— how and where to apply them.

By Byron E. Blanchard, N1EKV

Introduction

There has been a resurgence of interest in the phasing method of single sideband generation and reception as evidenced by recent articles and papers.1- 2'3 The portion of such SSB rigs that seems to be least well understood is the RF phase shifter connected between the local oscillator and the doubly balanced mixers. Various RF phase-shift networks are described in articles, but each seems to have shortcomings. Calculated component values must be modified in real circuits, and both phase and gain are sensitive to local oscillator level. 1 decided to try

1 Notes appear on page 39.

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