Diversity reception with the RSPduo is just a matter of activating one of that SDR's features.
I made the pictured module to house the SCPHS-180 surface mount component with its added parts. Either an adjustable gain amplifier or attenuator is needed to match signal levels from two different antennas. I used a 0 - 18 dB Kitz Technologies KT-501 amplifier along with a 9 dB fixed attenuator to provide +/- 9 dB of level balancing. A Blonder Tongue DGS-2 combiner combined the two signals. That can be used with any receiver.
My primary concern was in combining the two antennas to provide an attenuation notch on a strong signal. The RSPduo can automatically match phases and amplitudes to provide the best reception of the strongest signal. A 180-degree shift after that will be where the null of that same signal will be. For best performance either way, it is best to roughly match the signal level of the two antennas before beginning. That is more important when using the SCPHS-180 phase shifter. With that done first, a phase adjust alone will provide a good null. Then fine adjustment of the amplitude and phase controls perfects the null.
What I was expecting occurred--the performance of the two methods closely matched. That was most easily seen in trying to receive a weak signal under a strong local. Both methods had that weak signal cycling in and out of reception. A moderate strength wind was moving the driven element (around 15 feet away from the mast) enough to have a phase sift sufficient to change the level of the deep null on the strong local.
So, either way works well. It is obviously a simpler matter if you have a RSPduo.
My tests of the Kitz KT-501 amplifier showed it looking good. It has good sensitivity, a maximum measured gain of 17.2 dB, and an excellent
93.5 dB dynamic range making it hard to overload.
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