The ARRL handbook reports that the load seen by a modulation transformer is
simply the ratio between the final RF stage voltage and its current.

Somewhere else I read that the calculation result should be reduced by a factor
that varies with the RF stage operating class, i.e. 1.3 (class A), or 1.7 (class
B) or 2 (class C).

Even though, in practice, the load value is not critical, I wonder whether
anyone has got more information on the issue.

73

Tony I0JX