[Elecraft] K3/P3 S meter calibration

[Georges Ringotte F6DFZ]

Hi to the group,

I have a question about the S meter calibration.
On HF bands, It's on spot, very impressive indeed from S1 to end of scale, tracking my HP generator nearly perfectly ; S9 at -73dBm

However, it's not the same with the internal K144XV 2 m transverter.

P3 is good, -93 dBm at S9. The K3 is very poor, S3/S4 for that same level.

Do you have any explication ?

Best regards

Georges