[Elecraft] K3S IMD Questions

[Jim Brown]

On Tue,9/1/2015 10:44 AM, Ian White wrote:
> Today, anyone can make 2-tone IMD measurements using a modern SDR and a
> little care in setting up the input levels. The K3 itself provides the
> 2-tone test signal (CONFIG:2TONE On).

Yes and no. Let's not forget that the response of any measurement is the 
combined response of both the measurement system and the device under 
test (DUT).

An important test of any spectrum measurement system is its frequency 
resolution, which can be tested by its response to a steady unmodulated, 
unkeyed carrier. Like slide #8 in

http://k9yc.com/P3_Spectrum_Measurements.pdf

Likewise, we must qualify the dynamic range of the measurement system -- 
when does it begin to contribute distortion due to its own 
non-linearity. This is what K2XT ran into in his tests.


On Tue,9/1/2015 10:54 AM, Don Wilhelm wrote:
> Anyone who does such testing should also include in the report(s) the 
> power supply voltage as seen by the K3S alternate VFO B display.
> Lower power supply voltages will have worse IMD than voltages that are 
> higher.
> Running the K3 or K3S with a power supply voltage above 14.3 volts 
> will improve the IMD substantially.

Yes, the K3 and K3S are a bit cleaner with higher power supply voltage. 
K6XX showed this in a presentation to NCCC a few years ago. It's on my 
website.

All of my testing has been done with power supply in the range of 12.3 - 
12.6V.

73, Jim K9YC