I am trying to calculate Tsys for my 1.2m dish with Norsat 9000LDF LNB at 22GHz for water masers. Using SDR Sharp Signal Diagnostics I have obtained power level (amplitude really of 1.72 dB). I understand cold sky temp at 22 dB is 40K. Have I put the 1.72dB in right place and are results reasonable?

Yes, your spreadsheet is set up in the right way provided that the 1.72 dB is a power Y-factor. where (Y) must be a power ratio, not an amplitude (voltage)…