Farewell to the SunSDR2Pro; the Anan-10e returneth

After a week of using the SunSDR2Pro I began to realize that it wasn't the radio for me and I sent it back for a refund.The refund was issued quickly and with no fuss - I thank the vendor for that.

The radio itself seems to be a fine performer and does well pulling weak signals out of the air despite their being adjacent to stronger ones. That was the case during the All Asia DX Contest last weekend and the SunSDR2Pro did quite well on CW.

So why return it?

Elecraft KX2 spectrum measurements

I brought my KX2 in to work today and had a look at it on all bands.

I had measured it before on 80 meters but made the mistake of short-pressing the XMIT/TUNE button. A long press is required to cause the KX2 to transmit a carrier.

Rather than testing the rig with a 100mW output, I used 5 watts with attenuation on the input of the HP 8563A. Theoretically, any output should provide the same results (and probably do) but I wanted to test the rig at an output level more likely to be used for actual communications.

Comparing SDRPlay's spectrum analyzer function with calibrated HP8563A

With identical attenuators on each analyzer's input - and with the KX2 set for a 5-watt output, I re-ran the test comparing SDRplay's spectrum analyzer program with an HP 8563A. That program, intended for SDRplay' sline of receivers, can be downloaded here.

A previous comparison was made using the KX2's minimal output of 100 mW and with the rig being incorrectly keyed (misinterpretation of the XMIT/TUNE button) to produce a steady carrier.

The results below are an accurate portrayal of how each device responds to the KX2 on 3.5 MHz. The HP is calibrated annually and was last calibrated in Feb 2018 (four months ago) and it, of course, is displaying accurate results.

(For those interested, I also looked at the KX2's other bands and posted those plots here. Given the 10 MHz span of the SDRplay's Spectrum analyzer program, it is not possible to look at bands higher than 40 meters).
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HP8563A spectrum analyzer, 80m: second harmonic is 52.63 dB below carrier

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SDRplay's spec-an function, 80m: second harmonic is indicated (falsely) as being 41.9 dB below carrier

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Video: Flex 6300 vs. RSPduo

In this corner...weighing in at $265 - the (insert dramatic reverb) RSPduo from SDR Play (end reverb!).

With all the ingredients on hand I couldn't resist pitting David against Goliath. For the few weeks I've had the RSPduo, I've used it mostly to copy FT8 on various HF bands and 6 meters.

I had more in mind for it when I bought it but its performance is such that it's just too cool to let it run overnight or while I'm at work as it scoops signals from the ether. I look online periodically at the relevant websites - or the next morning - and am amazed anew.

At some point I started wondering how the Big Rig would have done in a similar time period on a given band.

A/B testing of receivers in a digital age

Over my many years in this hobby, I've frequently read reports, reviews and opinions on various radio's comparative performance derived by A/B comparisons with another rig.

Typically, the two rigs would be connected to an A/B switch so that each could be alternately connected to an antenna. The op would then listen and look at the S-meters as the receivers were tuned to specific stations. The result, minus QSB and QRM, would then be made obvious(?) and a write-up would inform us readers of which radio handled weak signals or near-by QRM better than the other.