Using WSPR and WD, we often find that sensitivity on the highest frequencies with the kiwi asks for additional preamps. We not only want to achieve some gain, but also keep IMD as high as possible while noisefigure of the frontend electronics as low as possible.
In the past it was very difficult to measure noise figure of some homebrew pre-amps precisely. We would need access to professional lab-equipment.
Today we have SDR's and digital signal analysis at our fingertips. SDRs can very easily measure the RMS Voltage of very small broadband AC-voltages in a known bandwidth...
A software who supports such measurements is offered by Dr. Thomas Baier, DG8SAQ - the auther of a very famous VNA here in Europe. He uses the soundcard for the measurements/analysis with this software called "Audiometer"
I mention it here, because noise measurements are one of the domains of WD and I personally have played a lot with WD's capability to precisely document the noise levels received by the antenna.
It is clear that I got interested to know the noise of the signal distribution system including the pre-amps at the frontend of the signal distribution.