This morning i made a test with 2 transformers back to back from 7-28MHz. TX : FT897 at 10 Watt FM. Output 40m : 5.5 Watt 30m : 6.0 Watt 20m : 6.5 Watt 17m : 5.75 Watt 15m : 4.8 Watt 12m : 4.8 Watt 10m : 5.5 Watt At 10 Watt the cores warm up so 10 Watt is the max. pep power for the BN43-202 More loss than i expected, about 50% at 2 cores Here is the output on 20m. This means a loss of about 25% in the transformer.