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Offline AllodiumTopic starter
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« on: July 25, 2009, 06:55:41 am »
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Has anyone ever tried using silver wire to make a detector coil?

Some people think that high-end speakers that use silver wire are just over priced, because the speed of sound travels though silver at 2680 meters per second and though copper at 3810 meters per second. But your not really dealing with sound, sound is just the end result, your dealing with a magnetic field produced by electricity.

The specific electrical resistance silver is 15.87 nano-Ohms per meter at room temperature copper is 16.78 nano-Ohms per meter.

I?ve tried replacing the windings of a dual silver coil Pevey speaker (that had blown) with copper wire, it sounded horrible so I replaced it again with silver wire and it sounded like a brand new speaker. The difference was the frequency response of the winding to the magnet, the silver had a more precise response were as the copper kind of just flopped around like a fish out of water.

So I?d think that silver would make a more sensitive detector coil as well.
I'll definitely try this some day. But if someone beats me to it or if it's already been done, than let me know how it works.

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« Reply #1 on: July 26, 2009, 02:05:16 am »
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Allodium;

Hmmmm silver IS more conductive, but isnt gold even more conductive?

The speed of sound, in the wire means nada, zip, nowt, nihil, nichivo, namowiyak. The speed of the ELECTRON wave front, in both metals, remains the same: nearly the speed of light. When you rebuilt with silver, you probably recentered the voice coil more perfectly, the tolerances, within that voice coil space, are so tight, its almost impossible to get it restored to the original alignment. Also, silver MAY be a touch lighter than copper.

Question: did you use the same diameter wire, in the copper coil, as the silver? Did you use a wire guage (Im being the doubting scientist here..... Im just trying to give you a hard time.)

A speaker coil, whether 4 ohms or 8 ohms or even 16 ohms is generally the dc resistance of the coil, so a copper re-winding would be above the proper impedance and would not match correctly, and the mis-match would reflect into the PA. A speaker designed for a copper winding can be just as good as one of silver. Its all hype.

Can you get insulated silver wire?

Detector coils are not made for high current (except P.I.) so there would not be an advantage.

Its an interesting idea to apply to P.I, though.

Brian AKA goldigger (why do I always have to be a cold water tosser? Why, why, why!) Crazy

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« Last Edit: July 26, 2009, 02:11:13 am by goldigger »
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« Reply #2 on: July 26, 2009, 07:01:29 am »
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Quote:Posted by goldigger
(why do I always have to be a cold water tosser? Why, why, why!) Crazy


Don?t feel bad, I actually enjoy constructive criticism. And to answer your questions...

Silver is the most conductive metal, followed by cooper and then gold, but gold is commonly used in electrical contacts as it is resistant to corrosion.

I used a gauge, and I used the same diameter wire.
I match the impedance by sacrificing a few turns (I can?t remember how many) and that may be the reason it didn?t work right.

You can get insulated silver wire here, although over priced.

I?m still a newbie as far as detectors go, but I?ve learned something from your reply.
First, I didn?t know there was a difference in current between PI and other detectors, I hadn?t got that far.
And second, I never thought that those few turns I left off of my coil may have been the cause of the problem.

Thanks,
   Allodium



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« Reply #3 on: July 26, 2009, 07:34:19 pm »
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Allodium;

Yes, those few turns would have reduced the magnetic field a bit, I would suspect.

Some of the THers, on here would probably argue that PI is an electrical field, well, yes, but it takes a high current pulse to develop it (VERY short pulse.) If you know how an ignition coil works, its similar..... Hey! I just said similar Wink

I can imagine using a small ignition coil with the search coil hooked to the high voltage, and a high voltage cap, at the coil/HV junction, of course its too simple.

I can dream, cant I?

The fact is, an ignition coil puts out 15,000 to 50,000 volts, at VLF frequency, for a very short pulse and dwell time is already known for a given make of coil. I just know this will cause a ruckus.

I dont believe that any gain, which you might get, using silver wire, would be reasonable, in face of the expense. Aluminum wire, although higher resistance (lower Q, can be compensated with a larger capacitor, somewhat,) would be lighter! THAT could be important.

Less back and arm pain.

I wasnt exactly criticizing but, in retrospect, I can see it would look that way, I meant to point out the difference between sound waves and electron flow, in any metal. ?? If you dug into the matter, there are probably surface sound waves and internal sound waves, at different speeds, just like there is a skin effect, at ac frequencies and the effect increases with frequency, this plays hob with the idea of speed of electrons through metal... its not in a straight line. It doesent have much affect a VLF, fortunately.

Brian AKA goldigger

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« Reply #4 on: July 28, 2009, 01:23:43 am »
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This has been quite an enlightening conversation, for me anyway.  Shocked

The reason I asked the question about using silver is because I'm building my first detector now, and I thought there maybe some benefit. But high voltage ignition coils sounds so much more interesting, although I'd think you'd need to haul around one hell of a battery to implement that.

I'm actually not that familiar with circuitry, not enough to debate the application of ignition coils. My profession is structural engineering, although I've repaired and fabricated my share or electronics. I still know nothing of designing them from scratch.

regards,
        Allodium

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« Reply #5 on: July 29, 2009, 10:08:22 pm »
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Allodium;

The ignition coil started as humour.... but whatheheck! I have a small coil I use for a fence charger, to keep the deer out of the veggy patch.... they wont touch the electric fence wire and I did not re-install it, this  year. This coil is tiny, maybe off a tiny foreign car or motor bike. I picked it up, many years ago, at treasure island. (the dump)

R/C afficionados use lithium batteries, these days, small, light and lots of reserve current and most important, a fast charge rate! P.I machines have a large dose of current, in that pulse, measured in watts, mostly.  2N2222 can develope 0.3 to 0.43 watts, without burning up, a big FET might develope a 2 to 10 watt pulse.

The pulse is very short so current flow very brief, but it adds up. Basically you want a brief, high magnetic field.... sounds like an ignition coil, to me! This (previous) discussion, gave me a thought that I want to check out, in relation to these aforesaid magnetic fields..... It gave me an IDEA! Shocked

Electronic circuitry must have a certain structure, to operate correctly, in that respect, it IS like structural engineering.... if it has a fault, it will fail.

Brian AKA goldigger Detecting



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« Last Edit: July 29, 2009, 10:10:56 pm by goldigger »
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Offline Eugene52
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« Reply #6 on: July 29, 2009, 10:41:02 pm »
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Quote:Posted by Allodium
Has anyone ever tried using silver wire to make a detector coil?

Some people think that high-end speakers that use silver wire are just over priced, because the speed of sound travels though silver at 2680 meters per second and though copper at 3810 meters per second. But your not really dealing with sound, sound is just the end result, your dealing with a magnetic field produced by electricity.

The specific electrical resistance silver is 15.87 nano-Ohms per meter at room temperature copper is 16.78 nano-Ohms per meter.

I?ve tried replacing the windings of a dual silver coil Pevey speaker (that had blown) with copper wire, it sounded horrible so I replaced it again with silver wire and it sounded like a brand new speaker. The difference was the frequency response of the winding to the magnet, the silver had a more precise response were as the copper kind of just flopped around like a fish out of water.

So I?d think that silver would make a more sensitive detector coil as well.
I'll definitely try this some day. But if someone beats me to it or if it's already been done, than let me know how it works.


Hello Allodium . The answer to your question is YES and it works Great .... Minelab uses a 99.9 % pure silver wire on their Commander series of search-coils . The wire is called "Litz Wire" and it reduces eddy currents which prevents signal falsing . The efficiency is increased thus creating more Transmit Power/ Greater Magnetic field .... So Allodium , you are creative like Minelab !!! See the link I posted :
Regards.......Eugene

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« Reply #7 on: July 30, 2009, 12:24:58 am »
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Thanks Eugene,
I'll try and make my own sometime, but until I get familiar with make coils I'll stick to copper.

Thanks goldigger,
I'm still liking the sound of ignition coils. If you don't try it, I will.

        Allodium

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« Reply #8 on: July 30, 2009, 12:55:28 am »
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Eugene52;

I think somebody is yanking your chain about silver litz wire. I think somebody told you an outrageous oxymoron untruth.

Litz wire has been around since the very earliest days of radio.... it was hair fine, multistrand copper wire, with a wrapped cotton cover. Are you saying they use hair fine, multistrand silver wire, with a cotton wrap??? Its hell to work with!  Wise

Litz wire is so fine, the resistance would be so high, that the Q of the coil would suffer. You dont want more resistamce, you want less. Think about it!

Remind me not to buy one of those machines. Multistrand is fine, for very high frequencies but at VLF frequencies its pointless, advertising hype, so is the eddy current bit; being silver wont make any difference, the small diameter will lead to higher resistance, even in silver. Shocked

I dont think you mean Litz wire, just that it is multistrand... what size??

Brian AKA goldigger

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« Reply #9 on: August 15, 2009, 05:46:54 pm »
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Goldigger
See you are a man of many trades  Wink
About the litz wire I have seen this used in dc/dc converters, but each strand of wire is insulated from eachother. By using this litz wire they bypass the problem of skin effect at the switching frequencies used. Thereby obtaining more efficient area of cable at the frequencies in question. I believe the frequency in question was about 20 kHz.
By the way, no need to use silver unless you can not carry the extra weight of cooper  Funny

do not know if this helped anyone but now it is said.

olsteffe (or steff as many people like to call me)

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« Last Edit: August 15, 2009, 05:49:43 pm by olsteffe »
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