[Elecraft] Re: K3 Audio

[Joe Subich, W4TV]

Do you have AFX "on" and are you looking at I/Q (left/right) from 
the K3?  The capture - including the small "spike" directly between 
the "real" and "ghost" signals looks like you are trying to process 
an unbalanced I/Q signal with the resulting improperly nulled image. 

73, 

   ... Joe, W4TV 
 



> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net 
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of 
> Alexandr Kobranov
> Sent: Wednesday, August 06, 2008 5:53 PM
> Cc: 'elecraft Reflector'
> Subject: Re: [Elecraft] Re: K3 Audio
> 
> 
> I just made two basic samples using K3 and TS-850 using Firebox 
> external soundcard and Winrad SW.
> 
> You can see screenshot from K3 line-out audio on
> 
> http://www.ok1kei.org/K3_audio/line_out_firebox_winrad.jpg
> 
> This is K3 with 400Hz roofing filter on some stable carrier. 
> LINE OUT setting on level 9.
> 
> Then the same signal with the same af level (no change in Firebox 
> input mixer settings) with TS-850
> 
> http://www.ok1kei.org/K3_audio/ts850_af_firebox_winrad.jpg
> 
> This is my TS-850 with 400Hz inrad filter and output from 
> phones jack. There are also some "ghosts" in af spectrum, 
> generaly more noisy, but 
> no "image" of passband af signal visible.
> 
> As I do not believe in overloding of the Firebox soundcard (the same 
> conditions for both RIGs so if overloded so in both cases...), there 
> is something to explain.
> 
> Comments?
> 
> Thanks for your attention,
> 73!
> Lexa, OK1DST
> K3/10 #727
> 
> 
> 
> 
> Alexandr Kobranov napsal(a):
> > I can confirm cca 20dB lower level of 3rd harmonics on front panel
> > phones output against rear panel line out. Main versus 3rd 
> harmonics is 
> > 50dB resp. 7OdB on line-out resp. phones output here.
> > Just tried with on-board sound card od my Dell workstation.
> > (using Spectran SW and output level adjusted for the same 
> peak out level 
> > on Spectran screen).
> > Maybe later will try with Firebox sound card which has 
> better parameters.
> > Lexa, ok1dst
> > 
> > Joe Subich, W4TV napsal(a):
> >>
> >>> There is still a bit of a problem on receive audio.  This has been
> >>> there for some time and exists in the form of harmonics.  The 3rd 
> >>> harmonic is quite easy to see and repeatable.  I used HRD to show 
> >>> this on the waterfall after a conversation with a friend. You can 
> >>> clearly see the harmonic at..
> >>
> >> You are overdriving your sound card or the line out transformer in 
> >> the
> >> K3. 
> >> I have measured the third harmonic using an audio spectrum analyzer
> >> at both the line out and headphone jacks of my K3.  Until 
> the level 
> >> becomes excessive (> .7V RMS on the Line Out) the third 
> harmonic is 
> >> more than 50 dB down (Line Out) and more than 70 dB down 
> (headphones). 
> >> 73,
> >>    ... Joe, W4TV  
> >>