Here are the results:
- SMA with only one ADF4350/ADF4350 is not recommended in this context due to lack of TG functionality. It does not allow to create an error map with the built-in signal generator and results using a cheap noise generator are poor.
- LTDZ has even worse peformance than the D6. I know the price is very tempting, but it is not very sensitive and has a noise floor of around -70dBm. You cannot use it on signals with less than -40dBm.
- The really good device is the NWT4000 by BG7TBL.
- The NWT and D6 can, in some cases, be a much cheaper alternative to a professional spectrum analyzer.