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Year in Review 2020 Diversity Reception

2020 diversity reception

I have been playing with dual channel SDR for a few years. But in 2020 diversity reception took a major leap forwards with RSPduo and phased array.

What a wonderful year. In August, I obtained use of an SDRplay RSPduo dual channel receiver. Its companion software enables the use to phase two channels, each with its own antenna, against each other. My first experiments proved that the RSPduo can be used to null local RFI as well as the ANC-4.

But my real leap forwards came in October with adding a second wideband loop to form a phased array along a 30 meter baseline. My wideband loop array provides excellent beamforming and noise nulling on medium and high frequencies.

To compliment the empirical results, I explain the math behind phasing two spaced antennas, and used an Excel spreadsheet to calculate array factor and antenna patterns.

So for me, 2020 diversity reception really ended the year on a high note. Several years of imagining came together with a working system that’s probably as good as you can build on a small city lot. The RSPduo is everything I could ask for on HF, while the Afedri dual channel really shines on medium wave, including Trans-Pacific DX from Japan and Korea.

My dual loop array is oriented for east-west endfire patterns, but also provides some north-south directivity in broadside mode. I also find it really neat to change antenna patterns in software by manipulating I/Q data on the computer screen.

Year in Review 2020 Diversity Reception – End of the Road

Unfortunately, having achieved these milestones, I can’t think of any more experiments or improvements in this area of my radio hobbies. Other than just using and enjoying the system, of course.

I would encourage hams and shortwave listeners to build and experiment with wideband active loops, dual channel receivers and phased antennas. You will find these to be good low-cost investments with a high return.

You can also use an active loop array for ham radio receiving, especially on lower HF. But that will require some stringent transmit-receive switching, possibly including powering off the active antenna amplifier while transmitting with anything more than QRP.

One comment

  1. Davie Aichelman says:

    Hi John, I have been using an Afedri 822X SDR for about 6 years also. Because of local RF here in Grants Pass, Oregon I mostly use a pair of 50′ spaced Wellbrook 1530LN loops with either traditional phasers (Wellbrook-Mizek), coax or LC delay modules or the Afedri 822X. As you have noted they all seem to work about as well, except traditional phasers do introduce more attenuation than either the coax delay or Afedri with digital phasing.

    I tried SDRdx and PowerSDR but didn’t like the busyness of either, but do use HDSDR. I don’t have an RSPduo or SDRuno software and was curious about both, although I don’t like what I have seen of the SDRuno software.

    Did you know that the Afedri utility that comes with the 822X SDR has phasing built in? For me it works as well as the other software I have tried, with an average of 30db nulls. I mostly use phasing for MW DX. As I understand it from Alex of Afedri, the 822X in dual diversity mode can’t control the gain of individual channels and only uses the built-in AGC, which seems to work well for matched loops at least. I think I remember that the channel gain can be controlled in single channel mode. I wondered if the RSPduo had more control and was worth getting because of that.

    I noted the you like the RSPduo for SW listening and the Afedri for MW DX. Why is that, I ask? For me the thing missing with the Afedri is full band coverage, which is why I wondered about the RSPduo. I think the Duo has full MW coverage in Diversity mode. Any comments on that would be interesting.


    Dave Aichelman N7NZH Grants Pass, Oregon

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