Re: : K3 receiver noise - my test results (long)

Posted by ab2tc on Dec 20, 2009; 8:03pm
URL: http://elecraft.85.s1.nabble.com/Re-K3-receiver-noise-questionable-test-results-tp4192141p4195779.html

Hi,

Is it just me that have two fairly strong audio spurs at 3.9 and 7.8kHz? By "strong" I mean about 70dB below an AGC saturated CW tone. This is on the line out. The level of these tones are independent on RF gain setting and also independent of the CONFIG:LINE OUT setting. My line out is set at "nor 016" which is low enough that transformer distortion is fairly minimal. I do not hear these tones on the front headphone output which is where I do all my listening, but I have made no attempt to perform any measurements on this output. The tones are definitely from the K3 as they disappear when I turn it off.

Look here for a spectral display of my line out with an XG1 generating 50uV:
http://ab2tc:82/pictures/k3_line_out_50uv_lev016.png

Don't get me wrong. This is fairly clean and I am not of those who perceive the K3 RX audio as "harsh" or "noisy". But I would like the ability set the AGC threshold higher. Even the 008 setting is a little too lively for me on 20m and below (Preamp off of course). BTW 15m is starting to come back to life, but there is disappointingly little ham activity on it.

Knut - AB2TC

Joe Subich, W4TV-4 wrote

That's fairly clear but since 1600 Hz to the top edge of the
passband is less than one octave it is difficult to determine
if the roll-off is "pink" (-3dB/octave) or "brown" (-6db/octave).
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