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Author Topic: Silver Pated Coils  (Read 3339 times)
AA5WG
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Posts: 496




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« on: April 29, 2013, 05:27:06 AM »

Hi to all,

How thick is the silver plating for "typical" ham radio HF amplifier coils?

Thank you,

Chuck
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KA4POL
Member

Posts: 1982




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« Reply #1 on: April 29, 2013, 07:24:51 AM »

About 0.4┬Ám.
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AA5WG
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Posts: 496




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« Reply #2 on: April 29, 2013, 07:36:34 AM »

KA4POL,

Hi KA4POL,

I did a conversion of .4um and it came to 1.575 inches.

Did you mean .001575 inches thick?  Is there a reference for
silver plating these coils?

Thank you for your help.

Chuck
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KB9VGE
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Posts: 24




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« Reply #3 on: April 29, 2013, 07:41:11 AM »

I did a conversion of .4um and it came to 1.575 inches.

Yup; Thats about right. 
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WB6BYU
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Posts: 13250




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« Reply #4 on: April 29, 2013, 08:09:04 AM »

Quote from: AA5WG

I did a conversion of .4um and it came to 1.575 inches.



I think you slipped a decimal point somewhere...

1.575 inches is 4cm.  From cm to um is a shift of 4 decimal places, then add
one more because the original was 0.4 rather than 4.  So your answer is off
by 5 decimal places.
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GW3OQK
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Posts: 145




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« Reply #5 on: April 29, 2013, 10:26:34 AM »

How best to clean such coils on a roller coaster especially the sides between the turns, without removing the 0.4 micrometer? I have one that looks tarnished.
Andrew
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KA4POL
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Posts: 1982




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« Reply #6 on: April 29, 2013, 10:28:02 AM »

1 micrometer = 3.9370079 x 10^-5 inch

Sorry for not saying more in my first posting. One thing is obvious, it is a real thin layer. Copper on PCB material is usually 35 micrometer, about 0.0014 inch.
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KE3WD
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Posts: 5689




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« Reply #7 on: April 29, 2013, 03:16:30 PM »

How best to clean such coils on a roller coaster especially the sides between the turns, without removing the 0.4 micrometer? I have one that looks tarnished.
Andrew

The tarnish of silver does not affect its conductivity. 

It just looks "dirty" to we humans. 

You can leave it as is and not worry about such. 

If you absolutely have to clean it, use a product called, "Tarnex" and just put some of this marvelous liquid on the end of a cotton swab and wipe the tarnished areas.  This does not remove any silver, it just chemically reverses that tarnishing corrosion back to shiny silver. 

Be sure to RINSE the silver wiped areas thoroughly with distilled water and cotton swabs as well. 

If you are experiencing electrical dropouts, it is very unlikely due to black silver tarnish, but may just be dirt.  Cleaning with 91% isopropyl alcohol, again on a cotton swab, followed by greasing the roller contacts usually clears that right up. 


73
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G3RZP
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Posts: 4589




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« Reply #8 on: April 30, 2013, 01:06:34 AM »

More available in the UK is Goddard's Silver Dip for a liquid - apply with a Q tip, or Goddard's silver polish. I think they do an impregnated cloth as well.
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K1ZJH
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Posts: 984




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« Reply #9 on: April 30, 2013, 07:23:19 AM »

Silver tarnish caused by sulfur dioxide in the air isn't conductive. It depends what caused the patina.

Pete 
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W6RMK
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Posts: 651




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« Reply #10 on: April 30, 2013, 07:21:12 PM »

Skin depth in Silver at 30 MHz is about 11.6 microns (0.4 mil).  At 3 MHz, 3 times that (*sqrt(10)).
http://www.microwaves101.com/encyclopedia/calsdepth.cfm

So if the plating is 0.4 micron, as given by KA4POL, you might as well not plate, because that's not even 5% of the skin depth.  Most of the current is flowing in the copper.  And if you had a nickle plate on the copper before the silver, it's even worse. A nickel "flash" is often done to help the adhesion, if it's going to get at all hot.  (and if you're plating aluminum, for instance in waveguides or chassis, they almost always do a nickel flash, because the copper diffuses into the aluminum)


Start getting up into UHF and it might be more worthwhile.. 300 MHz has a skin depth of 3-4 micron, so a really heavy plating would help.  At microwave frequencies (say, 7 GHz and up), silver plating is definitely worthwhile (at 30GHz, 1mm wavelength, skin depth is 0.4 micron)

The real advantage of silver (or gold) plating is that it is easier to solder to, because either it doesn't corrode/oxidise as much and if it does, the flux cleans it up much easier than copper oxide, sulfide or carbonate, all of which are very tough.

you might also look at:
http://www.w0qe.com/Technical_Topics/inductor_Q_tests.html

Silver does look pretty though..
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AA5WG
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Posts: 496




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« Reply #11 on: May 07, 2013, 06:48:01 PM »

Thank you to all for your input on silver plating.

Chuck
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