It would be nice to see this problem with the the K3IO board addressed
at some point. It may be, as Jim K9YC has hinted, related to core
saturation from low frequency components that could attenuated before
reaching the board. Or it may be that the transformers that fit in the
space are as big as they can be, and a third-party outboard audio
amplifier and isolation board is necessary, bypassing the transformers
in the K3.
But whatever the solution is, I'm looking forward to it, as using PSK
with a waterfall display on the K3 requires me to ride the AGC, LIN OUT,
and filters in a way that I didn't on the K2.
Leigh/WA5ZNU
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
Directory http://www.g4ilo.com/kcomm.html KComm for Elecraft K2
and K3
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