Intermittent broadband noise, possibly from high voltage lines, periodically pests the MW band here. In fact it covers most part of the SW band up to 8 MHz as well. Unwelcome as the noise is, it still gave me the opportunity to test the noise blankers issued with ExpertSDR2. They are also available in the dll for HDSDR.
Short version: The RF noise blanker works, and works well! It is possible to adjust the effect of the noise blanker. Easily available in HDSDR, a bit convoluted in ExpertSDR2. This turned out to be quite important in order to find the best balance between noise level and audio quality.
The two jpgs below show the MW band with (above) and without the NB algorithm activated.
Admittedly there is a range of a 100 kHz or so with no noise, where the NB is not very efficient, but the overall impression is very good. An audio example from 999 kHz is quite convincing.