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Author Topic: SOLID SILVER KEY CONTACTS - WHY?  (Read 4058 times)
K7NSW
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Posts: 87




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« on: May 17, 2015, 08:57:24 AM »

I look at various key manufacturers web pages and see that solid silver key contacts are always used in the more expensive keys. Why is solid silver important in key contacts? Why not silver plated? What is wrong with other less expensive metals? Rust? Well, silver oxidizes and needs burnishing too. Why not stainless steel?
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KA6TPR
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« Reply #1 on: May 17, 2015, 10:08:12 AM »

Silver nickel or silver platinum or silver copper alloys are harder; less wear than many low resistance metals, still has low contact resistance, and high resistance to arc erosion.  Doesn't easily oxidize, but will form sulphide films.  Coin silver is about 90% silver and 10% copper.
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K8AXW
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« Reply #2 on: May 17, 2015, 10:22:20 AM »

Silver plating disappears after long usage and multiple cleanings.  Solid silver lasts forever.
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A Pessimist is Never Disappointed!
N3QE
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« Reply #3 on: May 24, 2015, 12:49:03 PM »

Well, silver oxidizes and needs burnishing too.

For "classic" rig keying voltages and currents, the little spark at make/break on silver contacts blows them clean of oxide/sulfide films automatically.

The "spark blows the oxide film away" effect is probably not as useful with modern 5V low-current keying circuits. Punch-thru voltage for the sulfide film can be 10V-12V. (and I note that many modern rigs make an effort to put 12V at reasonable current through key contacts to help take advantage of this effect). Nice writeup at http://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=13C3236_AppNote&DocType=CS&DocLang=EN
« Last Edit: May 24, 2015, 12:54:34 PM by N3QE » Logged
K0BT
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« Reply #4 on: May 24, 2015, 04:37:47 PM »

Silver plating disappears after long usage and multiple cleanings.  Solid silver lasts forever.

I cringe every time I read a classified ad for a nice key where the seller has, "freshly burnished the contacts".  I imagine someone using 600 grit sandpaper...
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W9OY
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« Reply #5 on: May 26, 2015, 08:12:25 AM »

Silver Oxide is conductive and silver is the best conductor.  Keys typically do not give square waves with closure but a train of pulses called switch bounce.  The bounce tends to modulate what ever stage is connected to the Key so you want to minimize the bounce and try to get something as close to a square wave as possible

73  W9OY
« Last Edit: May 26, 2015, 08:31:12 AM by W9OY » Logged
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