  The high frequency primary power standard is univocally realized by means of
a coaxial microcalorimeter, at least up to 40 GHz. The coaxial microcalorimeter
is a broadband measurement system adjusted for effec-tive efficiency
measurement of power sensors both of bolometric and thermoelectric type. The
critical point in the power standard realization is in the determination of the
calibration constant g of the microcalorimeter, a frequency dependent parameter
that has huge impact on the accuracy as-sessment of the standard. The paper
proposes a simple but powerful way for improving this accuracy by using the
reference values provided by in-ternational key-comparisons which the
microcalorimeter was involved in.
