[Elecraft] K3 - FT8

[Don Wilhelm]

Alan,

How high is the input level to the K3 Line IN?  I am wondering if you 
are driving the transformers in the audio in slightly into saturation.

Try lowering the soundcard output and increasing the LINE gain.

73,
Don W3FPR

On 5/14/2018 3:05 AM, Alan Ibbetson wrote:
> Don,
> 
> I'm puzzled you when you say
> 
> "If it were a K3 problem, that aliasing would also be happening with 
> other  data modes as well. Other soundcard data modes do not have a 
> problem with a TUNE at 1000 Hz"
> 
> I can reproduce this problem with my K3 with MMVARI on other data modes. 
> I have tried it with another PC and sound card and again I can still see 
> the problem. So I suspect that feeding a pure sine wave from any source 
> into LINE IN can cause ALC bargraph artefacts at certain specific audio 
> frequencies.
> 
> This is not FT8 specific, nor is it audio harmonics or IMD. It is simply 
> an unfortunate choice of audio tone frequency interacting with the K3 
> internals. Or at least that is my best guess from the evidence I see 
> here. The only constant throughout these tests is my K3. If it is faulty 
> then OK, no big deal.
>