What techniques are used for diversity reception with CW or SSB? I am
familiar with AM diversity, where the agc's of the receivers are tied
together and the audio outputs are combined and fed into one audio amplifier
and speaker/phones. The receiver with the stronger signal generates the
agc, which reduces gain in both receivers, so that the one with the least
signal is partly muted and therefore noise output is reduced. With AM using
a diode detector, the phase of the audio is unrelated to the phase of the rf
signal, so the audio can be successfully combined without much difficulty.
With SSB and CW, which use a heterodyne detector that mixes the signal with
a local oscillator, the phase of the audio output at the detector is a
direct function of the phase of the rf signal at the antenna. If you try to
combine the audio from the two receivers, there will be phase cancellations,
so that adjustment of rf phase becomes extremely critical, much like
adjusting the phases of the noise and signal antennas on the MFJ or similar
noise canceller. Has anyone figured out a way around this difficulty?
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