WSPR performance disappointment
I just began testing a new KIwiSDR for WSPR decoding, and have been disappointed by the low WSPR spot counts versus other SDRs, when attached to the same antenna. In comparison to an Airspy HF+ the spot counts are roughly 30% lower with the Kiwi. Wondering if the Kiwi is simply less sensitive than other common SDRs, in which case I'll need to consider an LNA. The antenna is a random length dipole (138 foot total length), with a Cat 7 ethernet feedline, and a video balun (used for ethernet to video cable installations) at the antenna input. It works beautifully with my Airpsy, SDRPlay, and RTL SDRs. In addition, subjectively when listening to weak signals the KiwiSDR sounds significantly noisier than other SDRs.
On the other hand, I am not helping things by using a switching power supply to power the Kiwi. But with the antenna input terminated with a 50 ohm SMA load the noise floor is nice and quiet and flat, generally below -110 dBm. I would have expected that switching noise would be manifested as assorted noise spikes or blobs in the spectrum.
I have a lot more testing to do, but just wanted to post some early thoughts to tap into the community wisdom here.