I had a conversation with Hans about this, and it was our feeling that it was probably not worth the extra overhead and additions to the hardware, since the K9HZ amp is running in a much more linear mode than other MOSFET amps. As proof of this, look at the attached Two-Tone test with that amp. We are getting 36 dBC of separation of the 3rd order IM products compared to the carrier. That is generally considered "Very Good". This is about what Hans reported for his amp with the Polar Modulation. Better than -40dBC is usually considered "Excellent".
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To accomplish the amplitude portion of the Polar modulation would require some hardware changes, if I understand the process correctly. The power supply voltage is varied to accomplish the amplitude modulation in Han's scheme.
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However, the predistortion process would probably be beneficial and does not require more hardware - just some careful measurements.
Regards,
Al
AC8GY
