Video: QMX+ receiver sensitivity comparison with KX2, FT-891

Receiver sensitivity of the QRP Labs QMX+ is currently being discussed on the QRP Labs forum with at least one member of the group is disappointed that the MDS value of the QMX+ isn't published.

With the QMX+ being a kit, any published value of MDS would have to be a range of fluid values since receiver characteristics will depend, not only on component tolerance deviations, but of builder's methods in soldering and the winding of toroids & transformers.

I decided to compare my QMX+ receiver sensitivity with the KX2 and FT-891, using a TinySA Ultra and appropriate attenuation.

As can be seen in the video below, the QMX+ does quite well.

After the video, I "measured" (by ear) the point at which a signal becomes too weak to copy on the other bands. The CP1 directional coupler does not cover 6 meters but I measured -113 dBm on that band, which is probably inaccurate. I will sweep the coupler on 6m with my VNA and post a corrected value soon.

Directly on YouTube

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