[Elecraft] Re: K3 Audio

[Alexandr Kobranov]

Hello,

last test to test possible AGC influence on ghost signals is here

http://www.ok1kei.org/K3_audio/line_out_agc_off_500Hz.JPG

K3 has AGC OFF and signals are shortly invoked on/off by RF GAIN knob.
Line out is on 4, BW 400Hz (as roofing filter)
Spectrum is wider to see 500Hz original and then signals around 1.5, 
2.5 etc kHz.

Without changing of soundcard input gain the same performed with TS-850

http://www.ok1kei.org/K3_audio/ts850_agc_off.JPG

Also AGC OFF and af signal invoked by RF GAIN knob.
There are no ghosts visible.

(please ignore some permanent birdies on both pictures, look for 
signal on/off and ghosts on the right from original signals)

So as AGC was completely OFF, signal generator was used and in both 
cases the same soundcard setting was used and the same SW, there is 
probably some source of K3´s ghost signals in DSP demodulator itself.

Using so wide specrum (up to 5kHz) is only to illustrate how many and 
where all ghosts are...
Hope somebody with less "amateur" approach can comment/explain.

73!
Lexa, ok1dst
K3/10 #727
K3 GhostBusters Club


n4lq napsal(a):
> I see the same extra stripe using mixw  and an RF generator. I had to 
> turn down the line out of the K3 to 001 and crank up the sound card to 
> max inorder to eliminate it. The level is a bit weak now and needs more 
> gain. There is something not quiet right here.
> Steve Ellington
> N4LQ at insightbb.com
> ----- Original Message ----- From: "Jim Brown" <jim at audiosystemsgroup.com>
> To: <elecraft at mailman.qth.net>
> Sent: Friday, August 08, 2008 1:19 PM
> Subject: Re: [Elecraft] Re: K3 Audio
> 
> 
>> On Fri, 08 Aug 2008 09:30:55 +0100, Andrew Forrest wrote:
>>
>>> It appears that this effect is nothing to do with clipping or
>>> transformer saturation but some kind of mixing.
>>
>> I'm also not convinced that this particular screen shot is non-
>> linear distortion. It could be aliasing in the FFT software that's
>> part of the decoder.
>>
>> On the other hand, the pdf below DOES show both harmonic distortion
>> and IM distortion on the Line Output when the Line Out level is set
>> too high (driving the transformer being driven beyond it's ratings).
>>
>> http://audiosystemsgroup.com/K3FilterStudy.pdf
>>
>> 73,
>>
>> Jim Brown K9YC
>>
>>
>>
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> 
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