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    SDRPlay RSPduo SDR

    Recently, I had an opportunity to use this SDR in diversity reception mode on the NOAA Weather channels. I posted some comments about it in the `Your Weather Radio and 30-50 MHz Utility DX` forum.

    Interesting experience and a whole new world of DXing.

    73, Mark, N2MH

    I also have the Duo and the phasing on FM stations with diversity is just amazing. I've never tried it for weatheradio but I should since just about every frequency has something strong on it plus I have a local 4 miles from my house on Soapstone Mtn in Somers. The past two days I've been playing with SDRConnect. Diversity mode is stunning with that new software also.
    Enfield, CT USA
    Visit Mike's DX at or go here.

    On the web since 1999! (that's 23 years!)
    See what else I have over there


      I made a comparison of diversity reception with my RSPduo and my Mini-Circuits SCPHS-180 phase shifter.
      Click image for larger version  Name:	MFC SCPHS-180 Phase Delay.jpg Views:	0 Size:	58.4 KB ID:	1435

      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.
      Last edited by WHJ; 12-10-2023, 03:41 PM.