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
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