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Using the SDRPlay RSPduo SDR on NOAA Weather Radio

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    Using the SDRPlay RSPduo SDR on NOAA Weather Radio

    A couple of months ago, I picked up an RSPduo sdr from HRO. The RSPduo is made by SDRPlay. One of the things that sets the RSPduo apart from other SDR's is that it has two identical SDR receivers in the one box. Not only are there two receivers, but they are clocked from the same source and are phase coherent.

    A neat feature in the associated software, SDRuno, is the ability to phase one receiver against the other receiver to provide diversity reception. Diversity reception is the ability to have two (sometimes more) receivers at one location, tuned to the same frequency, be able to pick up various portions of a transmission due to some difference in their antennas. This difference in antennas could be two antennas separated by some physical distance or two antennas with different polarities (vertical and horizontal).

    During the past several days here on the North Carolina shore, we have had some coastal ducting. As coastal ducting goes, it wasn't very much. Stations about 100~150 miles away were being heard. But, this presented an excellent opportunity to test out the diversity reception on the RSPduo. On several channels, multiple stations were being heard and causing hetrodynes between themselves. Using the phasing control in SDRuno, I was able to peak up on station over the other to the point where the other station was simply not heard. Rotating the phasing control dropped the one station and peaked up the other station. In addition, the waterfall clearly showed the number of stations that were coming through on any one frequency. Most of the time, it was only two stations. One channel showed about 5 different carriers. You can imagine what the jumble sounded like.

    The most impressive thing was that this ability to hear stations actually worked on my local NWR frequency, 162.550. I live about 15 miles from KHB31 in Wilmington, NC. At that distance, they are a flame thrower. In spite of that, the phasing control was able to peak up KHB29 in Charleston, SC, some 113 miles away. At another time, I was able to hear WXJ22 in Florence, SC just as clearly. WXJ22 is about 92 miles away.

    For antennas, I have two gain verticals separated by abut 16 feet at a height of around 40 feet above ground, about 1 mile from the Atlantic Ocean.

    Bottom line: this phasing stuff rocks!

    73, Mark, N2MH

    I have an RSPDuo that I use for phasing on FM and often it is magic. Especially during tropo openings. Currently, I have a 4 element AIS Yagi cut for 162 MHz, but plan to swap it for a six-element AIS version from Arrow Antennas. The 4 element will then be located about 50 feet away, both on small TV rotors. Can't wait to try phasing them against each other using the Duo. Great tool!