[Elecraft] K2, distorted audio signal

[W3FPR]

I can only guess, but the loose standoffs plus the bottom cover were 
likely providing a path for the VCO and the BFO to couple together - the 
frequencies are close together on 40 meters.

73,
Don W3FPR

On 7/31/2025 8:38 AM, Michael Carter via Elecraft wrote:
> Thanks, Don, for clarifying the board structure on the K2.  You noted that the top and bottom covers need not be installed for the radio to still work properly, and that is my recollection from repeated forays into my K2 for module additions, etc.
>
> So, going back to the original poster's (Wolfgang) observation that the two loose standoffs, after tightening and addition of the top-side lockwashers under the screw heads, appeared to be the cause of the transient distorted audio he experienced,  what might be the cause of the distortion?  Depending on the relative return current path impedances, there will be different amounts of current flowing in the return traces and broad area copper on the board itself if the board 'ground plane' is not electrically attached to the case metal directly under the standoffs.  Yet since the radio works perfectly fine without the covers attached, this suggests that the portion of the return currents flowing in the case metal is not at issue?
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