The RADIO page of EA5FY

These are the measurements made on a KL300 amp driven with 5W of an FT817 in PKT mode at all different HAM frequencies. I see that the input impedances "goes bananas" as the SWR rises and therefore the rig reduces the driving power. The amp is intended for CB and I am trying to refurbish it into an HAM amp.

I have been looking at the application notes of Motorola and they claim that input impedance of MRF455 is quite stable along frequency. Only the gain has to be reduced at lower frequencies. Another site describes also the problem of saturation of the output trafo and proposes a new design, but nobody speaks about the input trafo. Any suggestion?

The following oscilograms show at different frequencies the input and output signal of the amp with the proper V_be polarization circuit (added already to the amp; originally it was a class C amp). Input power was 5W which corresponds to 22.4V_pk at 50 ohm load. I detect a severe distortion on the input signal (also the output, but if the input isn't clean...)