I've made a number of measurements on the K3's audio output a few days
ago in CW mode and again today, this time with two close spaced signals
inside the SSB filter as well as a single tone.
Yes, there are 3rd and other odd-order harmonics and, to a lesser
degree, even order harmonics.
However, these harmonics are down between 45 and 50 dB from the desired
signal in most instances. That's quite a bit of odd order harmonic
suppression, well under 1% THD.
I can see intermodulation products and in-band artifacts with the AGC on
and quite strong signal levels. These are also quite a bit down from the
two tones, but certainly differ from the same signal levels applied to a
receiver with analog detection stages.
I cannot hear an objectionable beat note or rough audio, but I'm afraid
that I fall into the category of being old enough to not have great high
frequency hearing.
I'll put some of the audio spectrum analyzer captures up on my web site
later today or tomorrow.
Jack K8ZOA
Berni G0IDA wrote:
Thanks everyone for the replies.
I just would like to put this thread back onto its tracks..... The
problem is with CW (although SSB does suffer too) and the main problem
is that I can hear the 3rd harmonic which when mixed with the
fundamental makes a rough note on CW especially when tuning away going
up in frequency.
I only used the waterfall program to confirm and to see at which
harmonic it occurred and line levels, AGC, PC cards etc...etc... have
no baring on this as I'm not measuring anything, just confirming that
it is there.
I compared 2 K3s and both had the same effect.
I'm using a Hiel headset to listen to CW it is also noticeable on the
main speaker but less so due to its design.
When confirming on the waterfall and indeed with my ears the rig is at
default setting & no amount of tweaking helps. Even with 1KHz of
filtering a 3rd harmonic is present.
K9YC:
1) Yes
2) Line level is irrelevant as I'm just confirming that it is there
and at which harmonic so as to give feedback to the reflector.
3) as above.
N4LQ:
I agree with you, nothing seems to help and I've never had this with
the FT1000MP or my recent Mk v.
W4TV:
I envy the K3 you have.... as there is 3rd product distortion and
never had this on any other rig... could there be a "bad batch" or K3s?
Just like to re-iterate that the thread is not about how to set up
your PC/LINE OUT or IN not to get distortion, it is about 3rd harmonic
distortion present on the headphone socket and speaker with or without
default settings!
Jim:
PSK + RTTY might have its own problems & its not part of my
discussion, I'm trying to concentrate this thread on just one mode CW
where this problem is significant as at times it is unpleasant to
listen to. SSB also has this unpleasant distortion.
There is one option a friend suggested.... wait until I get older and
the hearing drops off in frequency.... at the moment it seems the only
option..hi..hi..hi..
73s
Berni
G0IDA
Jim Brown wrote:
On Mon, 01 Sep 2008 14:30:45 +0100, Berni G0IDA wrote:
I hope there is a cure for this as it's frustrating listening to CW
with this sort of distortion.
There are three things you should do.
1) Make sure that the AGC is on, and that the CONFIG AGC settings are
at the defaults.
2) Reduce the LINEOUT GAIN (on the CONFIG menu) to a value less than
about 4. This prevents distortion that could occur in the output
transformer.
3) Adjust the input gain of your computer so that you have enough
signal for the decoder to function, but not enough to cause distortion.
This should correct any problems.
73,
Jim K9YC
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