This is the final report on the APMP bilateral supplementary comparison in RF power measurement P1-APMP.EM.RF-S4. The purpose of the comparison is to determine the level of consistency of calibration results given by two national standards laboratories.This is a comparison of one of the high-frequency key quantities. The comparisonprotocol was based on that used in the key comparison CCEM.RF-K8; however,the frequency points differ. One of the participants, the National MeasurementLaboratory, also took part in CCEM.RF-K8.The travelling standard is a Hewlett-Packard 8478B thermistor mount, with a type-Nmale RF connector. The calibration factor is determined at a number of frequenciesbetween 30 MHz and 3000 MHz, together with an appropriate statement of uncertainty. Measurements have been made at a nominal power level of 1 mW. The valueof the reflection coefficient is also determined, as it is needed for the uncertaintycalculation.The pilot laboratory was the National Measurement Laboratory, in Australia, andthe comparison coordinator was the Measurement Standards Laboratory of New Zealand.This report contains a brief description of the measurement set-ups at each laboratoryand a summary of the associated uncertainty budgets. The actual measurementsfrom each laboratory are presented as they appear in calibration certificates fromthe respective laboratories.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the APMP, according to the provisions of the Mutual Recognition Arrangement (MRA).