Analogue Phasing SSB direct conversion receiver: (late 1970s)

This was a very successful breadboard project for 14 MHz. I achieved around 60db unwanted sideband suppression using a the 4 phase RC audio network originated by M J Gingell and described in the ARRL Handbook. I used diode high-level DBM’s with IN914 diodes, and twisted – wire quadrature 90 degree RF phase shift networks which were described in QST some years ago. I found it was necessary to control the output of the LO with AGC to preserve accurate phase and amplitude balance. I also found matched bypass and coupling capacitors helpful to avoid small unwanted phase shifts in the 4 audio preamplifiers between the DBM’s and the RC phase shift network I experimented successfully with a simple audio AGC system using a JFET as a variable resistance element with an op-amp. Simple systems like this can work very well but care is needed in design and construction. In recent years the R2 design published in QST magazine offered some good design tips (not tried by me).