The termination rating on isolators

    The termination rating on isolators must be sufficient to safely dissipate the reverse power that is expected to occur under normal or anticipated fault conditions. The reverse power will be determined by the power applied to the input port of the isolator and the mismatch on the output port. This reverse power will be dissipated by the internal termination. All units, except the drop-in and surface mount isolators have terminations rates at 100 watts peak and 2 watts average power. If frequency, bandwidth and size permit, higher peak and average power values can be specified. Average power ratings of less than 50 watts for the lower frequency standard isolators usually do not require cooling other than mounting to a heat sink. Higher power levels may require the termination be mounted directly to a heat sink or the use of other forms of cooling.

Allowances must be made for some degradation in isolation for the higher power rated terminations.