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Re: inductor problem
On Fri, 06 Apr 2018 16:49:17 -0700, Jim Thompson

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Polystyrene would melt. If I use any form, it will be ceramic,
preferably AlN.




--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: inductor problem
They publish models for those things. You didn't SPICE it?

Tim

--  
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
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Re: inductor problem

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Silver plate the wire. Or just try winding it with silver wire.




Re: inductor problem
On Saturday, April 7, 2018 at 10:21:48 AM UTC+10, tom wrote:
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Winding with silver wire might work. Silver-plating was popular early on, until somebody measured the conductivity of electroplated silver, which is less than that of solid copper.

Laser annealing of plated silver might work.

--  
Bill Sloman, Sydney


Re: inductor problem
On Friday, April 6, 2018 at 8:47:49 PM UTC-4, snipped-for-privacy@ieee.org wrote:
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Huh, that's weird.  You figure the first guy to try silver plating  
copper would measure the resistance.  

George H.  
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Re: inductor problem
On 04/07/18 12:32, George Herold wrote:
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Silver oxide is a conductor, so if you keep sulphur out of the box, the  
conductivity holds up better over time.  Silver-plated connections also  
exhibit lower transient intermodulation at high powers.  (Nickel plating  
is a disaster for that.)

Cheers

Phil Hobbs


--  
Dr Philip C D Hobbs
Principal Consultant
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Re: inductor problem
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Why do people keep saying that, anyway?

I'd rather have insulating corrosion -- it doesn't have any effect on the  
fields!

Either one is bad for _connectors_, with one being worse than the other.  
But plated parts?  Conductive oxide is like nickel plating on top!

Given that the silver plating is thick enough not to corrode through, of  
course.

Tim

--  
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
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Re: inductor problem
On 04/08/18 11:38, Tim Williams wrote:
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But it isn't insulating.  Copper oxide is a semiconductor.  Silver oxide  
is very thin, because silver is a noble metal.  Corrosion roughens the  
surface and degrades the conductivity of the first few monolayers of  
metal, both of which increase loss.

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Nickel is bad because nickel oxide forms tunnel junctions so easily.  (I  
used to make Ni-NiO-Ni tunnel junctions for a living.)


Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: inductor problem
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Now, roughness is a real argument.  I recall reading the AC resistance of  
PCB traces can be 2x or more, due to the surface treatment (oxide or just  
roughness) normally needed for peel strength.

But then, is a smooth patina okay?  Verdigris?  I suppose the metal-salt  
surface is always going to be rough, but it can be smooth at the wavelength  
in question, whatever that wavelength might be.  It might be a problem at  
30GHz, but at the 30MHz in this thread?  The poor thing would have to be  
hot-rolled for that to be a problem...

So aside from roughness -- /so what/ about insulators?  Everyone parrots  
that statement, but it doesn't check out!

Even semiconductors aren't a problem, as long as their resistivity is that  
many times the bulk metal's, so that a tiny fraction of signal current flows  
in them.

Seriously, I've done this before, on a much grander* scale -- I designed an  
induction heater that runs at two frequencies, for stirring (at low  
frequencies: magnetic field penetrates the graphite crucible) and gentle  
heating (at high frequency).

(*Grand, in the literal sense that the frequencies in question are >= 3  
orders of magnitude lower.  Power level is also higher, by a few decades I  
guess, but the system is linear enough not to care, so that doesn't matter.)


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That too.  But just on the matter of Q and power handling, it's awful  
because of its permeability.  You don't use nickel underplating in  
waveguides (at least, not without an unusually generous thickness of silver  
on top of it).

Tim

--  
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
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Re: inductor problem
Am 08.04.2018 um 21:09 schrieb Tim Williams:



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Also for uwave boards, Au over Ni is not an option.

Cheers,
Gerhard

Re: inductor problem
On Sunday, April 8, 2018 at 2:32:24 AM UTC+10, George Herold wrote:
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It's a rather small difference, and remarkably hard to measure.

That kind of precision resistance measurement is the sort of thing that national bureaus of standards do with ratio transformers.

--  
Bill Sloman, Sydney


Re: inductor problem
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So, wait, you're pulsing >200V across this poor thing?  More than 600VAR?  
And you're worried that it's getting "very hot"?

If it's not glowing red hot in ten seconds, I'm not disappointed, I'm  
impressed!

Tim

--  
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
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Re: inductor problem
On Friday, 6 April 2018 23:44:05 UTC+1, John Larkin  wrote:

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The resistivity & tempco of copper & silver are so close as to make no significant difference afaic tell. Parallel thinner wires give more surface area per xsa.


NT

Re: inductor problem
On 7.4.18 01:43, John Larkin wrote:
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Litz loses its efficiency above the MF range.

Get an ARRL handbook and have a look at the HF final amplifier
coils. They are usually made from copper tubing and maybe silver-
plated.

--  

-TV


inductor problem
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Getting rid of the tin plating would help. I'd add my vote for some nice fat magnet wire.  

How are you handling the EMC issues?

Cheers

Phil Hobbs

Re: inductor problem
On Sat, 7 Apr 2018 01:35:04 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

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Yes, but I may just need cubic inches to work in, which means a board
spin. Well, we sort of expected that. I could maybe use a forest of
old-fashioned axial-lead RF inductors.

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I'm not! That's the customer's problem; I'm just furnishing a PC
board.  

I tried to measure the top temperature of one fet; it felt pretty hot
but my Omega thermocouple meter insisted it was 3 degrees C.

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Easy for you to say.


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--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: inductor problem
On 04/07/18 11:44, John Larkin wrote:
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The tin is far lossier than the copper, and it's in exactly the wrong  
spot.  Even #22 magnet wire might be good enough.  Bare copper would be  
fine at first, but get worse as it tarnished.

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And repeat!

Cheers

Phil Hobbs


--  
Dr Philip C D Hobbs
Principal Consultant
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Re: inductor problem
On 2018-04-07 11:21, Phil Hobbs wrote:
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In this application even at low frequencies only as a space heater or  
for defrosting purposes :-)

https://www.engineeringtoolbox.com/wire-gauges-d_419.html


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I remember when we built our big fat shortwave power amplifiers for ham  
radio one of the most important items on the shopping list was metal  
polishing paste. For that reason. If you let the coil in the Pi-filter  
or the matchbox become too dirty someone might comment "Where does that  
amperage smell come from?".

Still using it and this is IMHO the best stuff for the job:

https://www.excitingcabinet.top/red-wenol-metal-polish-brass-copper-silver-stainless-steel-chrome-50ml-tube-p-15711.html

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Skol!

Currently enjoying a homebrew Autumns Amber Ale. Yes, I know it's only  
lunch time but it's Saturday and only half a stein.

--  
Regards, Joerg

http://www.analogconsultants.com/

Re: inductor problem
On 04/07/18 14:44, Joerg wrote:
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If your liver starts to suffer you'll have to go back to full-time  
engineering, though. ;)

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: inductor problem
On 2018-04-07 11:50, Phil Hobbs wrote:
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[...]

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No kidding, that was my concern when my ALT values kept being too high.  
However, months of total abstinence and diet changes did absolutely  
nothing. What the heck? Then I started bicycling again just to stay in  
shape. Bingo ... ALT value in the middle of the normal range. So ... I  
could happily brew now.

--  
Regards, Joerg

http://www.analogconsultants.com/

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