KX3 IM3 and IM5 measurements

[oe9fwv]

hi all,

we made 2 tone measurements of my KX3 and compared it with my FT-817.
There was one unexpected result with the KX3, and I would like to ask the group if this is
already known or looks like a problem with my KX3.

The IM3 peak is lower than the IM5 peak and it is asymmetric.

The first picture shows the KX3 alone with no PA:
http//oe9fwv.dyndns.org/oe9fwv/KX3/kx3_alone.gif

The second picture shows the KX3 connected to the Hardrock50 PA:
http://oe9fwv.dyndns.org/oe9fwv/KX3/kx3_HR50.gif

any comments on this phenomenon would be appreciated.

73! de Werner OE9FWV


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[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


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[Ignacy]

There are IMD graphs of KX3 at different power and voltage levels in FILES on KX3 group at yahoo. IMD3 levels sharply increase with higher power and lower voltage.

The IMD is are important only IMHO if KX3 is used at very high power level on a crowded band. It is irrelevant for QRP operation.

Ignacy

[wayne burdick]

Also, when the KX3 is used to drive a KXPA100, the rig is typically operating at well below maximum power, reducing IMD levels.

Wayne
N6KR


On Jul 14, 2014, at 7:47 AM, Ignacy <[hidden email]> wrote:

> There are IMD graphs of KX3 at different power and voltage levels in FILES on
> KX3 group at yahoo. IMD3 levels sharply increase with higher power and lower
> voltage.
>
> The IMD is are important only IMHO if KX3 is used at very high power level
> on a crowded band. It is irrelevant for QRP operation.
>
> Ignacy



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