[Elecraft] K3 Harmonic Distortion

[Joe Subich, W4TV]

Jim is entirely correct although we will disagree a bit about 
the need to keep the line out as low as he suggests.  My own 
measurements say the harmonic distortion is insignificant as 
long as the Line Out levels stay below .5V RMS.  

The headphone outputs are exceptionally clean as long as the 
audio amplifier level is kept below 2V peak (1.4V RMS) and 
the output impedance is not too low.  In fact, noise in the 
audio amplifier (headphones) is 70 dB below the desired (CW 
at 500 Hz) signal +/- 250 Hz and 80 dB below the desired 
signal above that.  All harmonics are down more than 60 dB 
as long as the headphone level is not at levels that could 
damage hearing (> 1.4V RMS).  

The headphone output in the K3 is cleaner than any amateur 
receiver I have seen and certainly better than the current 
crop from Ikensu or Yaecomwood. 




> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net 
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Jim Brown
> Sent: Monday, September 01, 2008 12:06 PM
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] K3 Harmonic Distortion
> 
> 
> 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
>