OK. . .
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90 degree hybrids with mulitoctave frequency are possible but this is the 21st century. . .
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Buy a dual channel SDR receiver with matching "IF signal handling" chains and create the 90 degree phase shift in the "digital" local oscillator.
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For that matter add a third antenna element and think about a quaternion signal detector with three LO's and three parallel if stages.
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Jim/VEZ
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James Redding WA9VEZ