Our own measurements
Relative noise measurements are not as difficult as absolute measurements done by PA0KDF. Absolute measurements need calibrated antennas and equipment. We use the active broadband small loop antenna and the SDRplay RSP1a receiver with the SDRuno software. The SDRuno supports a RMS noise measurement! Advantage of the loop is that it is well balanced and does not need a ground plane. That makes measurements reproducible. When using the same equipment on different locations the noise levels can be compared. PA0KDF has done measurements in Maasbree PH4RTM and in Kronenberg PA3ARM. We had these results as a reference for our own measurement set-up.