[Elecraft] KX3 IM3 and IM5 measurements

[Wayne Burdick]

Hi Werner,

> we made 2 tone measurements of my KX3... one unexpected result with the KX3...The IM3 peak is lower than the IM5 peak and it is asymmetric.


This is not unusual with MOSFET power amplifiers. We've seen such effects with 10- to 100-watt amplifiers made by various manufacturers. It's likely due to multiple IMD sources, including the PA stages themselves, class-AB bias, supply voltage dynamics, exciter drive level, low-pass filter matching, and impedance match between the exciter and amp. 

Depending on phase and amplitude of the contributors, IMD products from two stages may add together or cancel each other. The amplitude of resulting products is more important than any resulting asymmetry.

73,
Wayne
N6KR