[Elecraft] K3 related - non-linear audio transformer behavior

[Paul Christensen]

> That's why I question the applicability of a ringing test with a square 
> wave having a rise/fall time measured in nanoseconds, as the audio that 
> makes it through the K3's crystal and DSP will not remotely resemble that 
> waveform.

Agreed Jack, if the DSP and/or AF stages truly limit impulses through the 
transformer.  To Jim's point, ignore the modulation type for the moment and 
consider an impulse noise such as that created by the start of light switch 
or AC motor.  If the system received BW is wide enough (e.g., selecting the 
K3's 6 kHz, or especially the 12 kHz filter), I suspect that transient 
impulse response becomes meaningful.  I have not yet tried to sweep the K3's 
audio section beyond 4 kHz and the DSP and/or audio sections may preclude an 
audio response beyond that point.

One way of testing this is to turn on/off various types of real noise 
sources as a function of selected filter BW and while observing a scope on 
the output of the line-out transformer, record the differences in peak 
values with and without terminating resistance on the transformer 
secondary -- taking into account any level difference created by the 
addition of the terminating resistor.

Paul, W9AC