[Elecraft] K3 Harmonic Distortion

[Jack Smith]

I've found that the LIN OUT port has typical third harmonic levels 
around -45 dB from the fundamental, with the LIN OUT level set at 10, 
the factory default. The headphone port, under the same conditions, will 
show the third harmonic down about 70 dB or so at levels appropriate for 
my Sony high sensitivity headphones. Cranking the audio level up will 
cause higher distortion on the headphone port, but only at levels that 
are impossible to listen to as they are so loud as to  be unbearable.

I've also seen some non-harmonic artifacts, particularly when very 
strong signals are pumped into the K3's antenna port.

Jack K8ZOA

Julian, G4ILO wrote:
> I think it was me who used the term "ghost" signals when referring to the
> harmonically related CW traces I could see on the CW Skimmer display. I
> probably would have been completely unaware of it if I had never tried this
> program. It was only obvious as I was listening to CW with a narrow filter
> and the "ghost" traces were appearing in the part of the waterfall that you
> would be expect to be dark because it was outside of the passband. I would
> agree with the suggestion that the harmonics are at a low level relative to
> the main signal because they are masked by band noise when you open the
> filter up. I don't think there is much risk of calling someone on the third
> harmonic by mistake. I don't know what the voltage level of the line output
> is but the traces disappear if you turn the level down to 2, which
> unfortunately is too low for most sound card programs.
>
> I don't know if those same harmonics are present on the speaker or headphone
> outputs, as distinct from the computer audio feed. I can only say that I
> find the K3 audio exceptionally pleasant to listen to. I much prefer it to
> the K2, or the FT-817, which are the only other radios I have. The only
> other radio I have had that sounded as clean and low-distortion as the K3
> was an IC-756PRO that I had many years ago.
>
> If the harmonics are down by the kind of amounts that others have measured
> then the distortion figure is still within the specification for what after
> all is not meant to be an audiophile quality hi-fi output stage.
>
> -----
> Julian, G4ILO. K2 #392  K3 #222.
> http://www.g4ilo.com/ G4ILO's Shack   http://www.ham-directory.com/ Ham
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>