The monthly log file contains a field (23, "W") which is described in the Wiki as :
I am using a WH1090 (and have ticked the correct station type in the configuration menu). It does not have a solar sensor, yet the "W" field contains a value.Current theoretical max solar radiation (only valid if solar sensor on weather station)
Typically the values start 1 at about sunrise increasing to 121 (21 December) or 886 (1 July) at noon (UDT) then reducing back to 1 at sun-set. The value is 0 overnight.
What do these values mean?