[Elecraft] [K3] K3 Receiver Noise Level -- Evaluation andAdjustment

[Sverre Holm (LA3ZA)]

It appears that there are several sources for lines in the spectrum of the
output on the LINE OUT jack.
What I measured earlier today was at a LINE level of 015, at some value
above that one can see that indeed the harmonics of the signal spectrum
starts to appear -maybe due to some transformer effects as mentioned on the
list, but at my settings and at this line out level this is not the case.
Besides, I can measure something similar from the headphone output jack.

My original measurement with signal + unrelated line noise is here:
http://www.qslnet.de/member/la3za/bilder/K3-CW-spectran.jpg

Then I measured with the RF gain set to minimum, i.e. not signal:
http://www.qslnet.de/member/la3za/bilder/K3-no-spectran.jpg

But, I cannot say for sure that the K3 is the source of the line noise
(1,2,3, ... kHz) as it appears even if I unplug the minijack cable (even
with the K3 turned off), however at about 15 dB lower level:
http://www.qslnet.de/member/la3za/bilder/K3-noConnect-spectran.jpg

The only way to get rid of the lines is to unplug the cable at the PC-end:
http://www.qslnet.de/member/la3za/bilder/K3-noCable-spectran.jpg

So, for sure I cannot blame these lines on the K3 now, I need to understand
better their source before making any conclusions. Sorry if I have made
confusion on the list with these measurements.


-----
Sverre, LA3ZA

K2 #2198, K3 #3391
http://www.qslnet.de/member/la3za/K2/mod.html LA3ZA Unofficial Guide to K2
modifications 
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