Off and on for a year, I've had a scratchy noise with the volume turned down on my K2. There is a scritch-scratch with the onset of each CW element. It happens when the volume control is set between nearly off and 9:00, which is where I usually operate. The volume never goes completely off with the control set completely CCW. When I turn the RF gain control down and turn up the AF gain to make the signal as loud as it originally was, there is no extraneous noise. The AGC setting doesn't effect the presence or absence of the noise. The noise makes its appearance more often when the K2 is located in the Caribbean, working pile ups than when it is at home. The ambient temperature in the Caribbean is 30C, while it's usually 23C in my Milwaukee basement, and a lot less humid.
My K2 is serial number 2651. I performed the volume control mod a couple years ago, and this problem did not exist before or after I did it. I have recently double checked the audio circuits around the pot, and although all the solder joints looked good, I redid them anyway. I have the DSP unit installed. Interestingly, when the DSP unit is switched in to any level of noise reduction, the scratching goes away. So one would think something is awry earlier in the receiver. The noise seems complex. It's not very loud and doesn't keep me off the air, but it's irritating, especially when listening to weak signals. When there is no signal, and I'm listening to atmospheric noise at any volume level, there is never any noise. Whatever it is, it is triggered by the CW coming in. It seems it could still be "south" of the DSP unit as the signal coming out of that module seems to have its hard edges filed off.
The noise is "fine" in its texture and doesn't appear in the loudspeaker. I can hear it in different kinds of headsets plugged either into the front panel jack or the speaker jack on the back of the KPA100.
Ultimately, it's hard to figure this problem out at home as it's intermittent.
Any ideas? (Please respond to me direct as well as on the list as I receive it in digest form. Thanks!)
73,
Andy W9NJY
K2 2651
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