[Elecraft] K3 RX spurs

[Julian, G4ILO]

What output are you taking the audio from to plot these results? The line
output signal goes through an isolating transformer. I think this saturates
at quite a low audio level introducing non-linearity. You need to turn LIN
OUT down to 2 or as low as you can get.

I haven't done the test you did, but if I look at a CW signal with a narrow
filter selected I can see a ghost image of the signal on the waterfall at
twice the audio frequency, well outside the IF passband. So I think the
problem (if indeed it is a problem - nothing is perfect) is within the audio
stages and particularly the line output.


Ramiro Aceves wrote:
> 
> Hello K3 fans
> 
> I am a bit stranged and frustrated cause nobody has answered a single 
> word to my email "K3 RX spurs" posted on november the 20th. No comments, 
> no ideas....
> After some tests I have concluded that the spurs are 3rd order 
> intermodulation products. They only occur in DATA or CW.
> ¿Can anyone please, try to reproduce those products in your K3/P3 or 
> K3/computer combination?.
> 
> "DATA A" mode: Cristal filter= 2.7KHz, SHIFT=1.5 KHz, WIDTH= 2.7 kHz
> Tune some steady carrier in shortwave. Tune the signal to place a 
> beautiful 1000 Hz on the waterfall
> Tune your signal generator 10 Hz more than the broadcast carrier 
> frequency to get an audio  signal 10 Hz over the 1000 Hz signal. Adjust 
> generator strenght to be similar to the broadcast carrier.
> 
> You will see strong beautiful 3rd order products on 1020 and 990 Hz. 
> Swith to USB--> much more weaker 3rd order products or inexistent.
> 
> http://ea1abz.ure.es/3erd-order.jpeg
> 
> That is my K3 behaviour. Just want to know if my K3 is ok or not.
> 
> Many thanks. I appreciate your effort in doing this test for me.
> 
> 73, Ramiro, EA4NZ.
> 
> PD: Volume at the speaker is zero to avoid vibrations inside the K3 
> case.
> 
> 


-----
Julian, G4ILO. K2 #392  K3 #222.
* G4ILO's Shack - http://www.g4ilo.com
* KComm - http://www.g4ilo.com/kcomm.html
* KTune - http://www.g4ilo.com/ktune.html

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