[Elecraft] K3 Harmonic Distortion

Mon Sep 1 18:23:21 EDT 2008

> 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!

My point is that my K3 - s/n 622 (factory assembled) has absolutely 
no measurable harmonics on the headphone output unless I force the 
gain to a painful level.  I use external speakers (two) but have 
made my measurements from the headphone jack (left) - I have checked 
with both SPKRS=2 and SPKRS=1 as well as SPKR+PH in both Yes and No. 
I have also checked with all AFX options and see no difference. 

Two sample Audio Spectrum plots are attached or may be downloaded 
at: www.microHAM-USA.com/Downloads/K3_Headphone_No_Signal.jpg 
and: www.microHAM-USA.com/Downloads/K3_Headphone_out.jpg.  The 
"Headphone Out" capture is of an S-9 signal (1KHz audio) in 
DATA_A mode with AGC On, 2.8 KHz 1st IF filter and 2.8 KHz DSP 
bandwidth.  This shows signal at 70 dB above the noise floor, 
second harmonic at -73 dB and third harmonic at -81 dB with no 
intermodulation.  

I made similar measurements at 500 Hz in data mode and again all 
harmonic and distortion products are down more than 60 dB.  To 
confirm that the issue was not one that was present only in CW 
mode, I also made measurements at 500 Hz and 800 Hz in CW - again. 
2nd, 3rd, 4th, 6th, 8th and 10th harmonics were visible in the 

I will make similar measurements with a second K3 (s/n 1450) and 
KRX3 when I finish assembly.  

73, 

   ... Joe, W4TV 

> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net 
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Berni G0IDA
> Sent: Monday, September 01, 2008 3:20 PM
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] K3 Harmonic Distortion
> 
> 
> 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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