[Elecraft] [K3] Wetting current and CW paddles

[Rich NE1EE]

On 2020-10-15 11:51:-0400, Drew AF2Z wrote:
>I think there could be more than just clean contacts involved.

I suspect from my own undocumented tinkering that contact geometry is also involved. Back in the day when currents were higher, we'd burnish contacts to flat, parallel surfaces. The instruments and controls that I have in mind were routinely serviced. They were routinely serviced because contact were observed in DC control systems transferring metal from one contact to the other, resulting in a pit on one side and a peak on the other.

Perhaps modern key contacts can benefit from at least one of the contacts coming more to a point. This would increase contact pressure due to the reduced contact area, and would result in higher charge density near the tip, and therefore higher potentials as the contacts closed. Two factors: tip radius (smaller is better) and tip contact area (more is better).

I have found for some keys with metals that corroded more quickly that periodic light cleaning is all that is required, but for those keys with less active metals, reshaping worked well to reduce false contact closures. I still stutter on some occasions on all my keys.