[Elecraft] K3 RX spurs

[Ramiro Aceves]

Hi Julian

I am very glad to see that someone has replyied to my email.

I have LINE_OUT= "nor 019"

If I go down to 002 I need to rise gain at the sound card, and the 
intermods are the same.

http://ea1abz.ure.es/spurs.jpeg

This spurs seem to produce only if both test signals are close, closer 
than 50 Hz and in DATA/CW mode, not USB/LSB.

Do not think that this spurs will cause a problem in real life 
operation. Just curious about the DATA/CW vs LSB/USB diferences found. 
Perhaps a "pile up blur" will occur when many CW stations are very 
close, who knows ( do not know how to say it in english)

Thanks for your suggestions!

73, Ramiro, EA1ABZ.



Julian, G4ILO escribió:
> 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
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>