my DIY Surf PI 1.2 coil problem

[6666]

Shh don't tell anyone, this place has 26 gauge PTFE tinned wire...
http://www.surplussales.com/Wire-Cable/Wire4.html

Now if somebody was quick enough they could buy a bunch of that wire and sell it to US !!!!!!!

[porkluvr]

I got some. It wasn't tin. It was SILVER.

I'll sell it to you!

[gdogg]

hey guys, ive just bought some Litz wire, Minelab detector coil, from ebay

http://www.ebay.com.au/itm/251270393553

is it any good?

[Tinkerer]

Now if somebody was quick enough they could buy a bunch of that wire and sell it to US !!!!!!!

Is Teflon (PTFE) wire worth the higher cost?
If you take a PVC insulated fine strand wire with thicker insulation, like 600V instead of 300V, you get near the same result for inter-wire capacitance.

electric characteristics of twin-lead:
diamter of conductor: 0.40 mm
conductor spacing : 1.00 mm
di-electric material: TFE

capacitance 36 pF/m
inductance 0.74 uH/m (DC)
inductance 0.64 uH/m (HF)
characteristic impedance 133 Ohm (HF)
velocity rartio 0.69 (HF)
attenuation 0.011 dB/km/sqrt(frequency)




electric characteristics of twin-lead:
diamter of conductor: 0.40 mm
conductor spacing : 3.00 mm
di-electric material: PVC

capacitance 33 pF/m
inductance 1.18 uH/m (DC)
inductance 1.08 uH/m (HF)
characteristic impedance 182 Ohm (HF)
velocity rartio 0.56 (HF)
attenuation 0.008 dB/km/sqrt(frequency)



This calculator can be found at:
http://www.mogami.com/e/cad/electrical.html

Also note, with the same calculator you can find the co-ax cable capacitance values. Compare with twisted lead!

[baum7154]

Is Teflon (PTFE) wire worth the higher cost?
If you take a PVC insulated fine strand wire with thicker insulation, like 600V instead of 300V, you get near the same result for inter-wire capacitance.

electric characteristics of twin-lead:
diamter of conductor: 0.40 mm
conductor spacing : 1.00 mm
di-electric material: TFE

capacitance 36 pF/m
inductance 0.74 uH/m (DC)
inductance 0.64 uH/m (HF)
characteristic impedance 133 Ohm (HF)
velocity rartio 0.69 (HF)
attenuation 0.011 dB/km/sqrt(frequency)




electric characteristics of twin-lead:
diamter of conductor: 0.40 mm
conductor spacing : 3.00 mm
di-electric material: PVC

capacitance 33 pF/m
inductance 1.18 uH/m (DC)
inductance 1.08 uH/m (HF)
characteristic impedance 182 Ohm (HF)
velocity rartio 0.56 (HF)
attenuation 0.008 dB/km/sqrt(frequency)



This calculator can be found at:
http://www.mogami.com/e/cad/electrical.html

Also note, with the same calculator you can find the co-ax cable capacitance values. Compare with twisted lead!

------------------------------------------

After having made several of these coils and experimenting with what makes them perform I only use the 600 volt or higher insulated PTFE because thicker insulation causes a significant decrease in capacitance and I'm detecting small 1/3 gram gold. I also use the smallest practical wire diameter (typically 26AWG) because larger wire significantly increases capacitance.

However, besides lower cost, another benefit of the PVC insulated wire is that it is readily available in tinned wire that is not available in PTFE wire. The silver plating of the PTFE insulated wire is required to prevent oxidation of the wire because of the high heat necessary for the application of the PTFE insulation. That said I have not seen any evidence of the silver plating of the wire causing enough eddy currents that interfere with detector operation. Once again I keep the wire size small as practical and this minimizes the eddy effect too.

The silver plating on stranded PTFE wire comes in two types. One is manufactured with the individual wires plated before stranding and the other is plated more heavily after stranding in order to prevent strand fraying when the wire is stripped. I only use the wire that can fray out of the bundle and is lightly plated.

If I decided to use PVC insulated wire it would have greater than 600 volt insulation if at all available and if the design could accommodate the thickness. Also the PVC insulation is much softer and crushable than PTFE so care would have to be exercised to insure that wire crossover tension would not be overdone. For me the PTFE is worth the cost. It only costs a little more to go 1st class!

Regards,

Dan

[porkluvr]

I got some. It wasn't tin. It was SILVER.

I'll sell it to you!

One of these days I will learn not to make arguments that cannot possibly be proved to be true.

Here is the source of my "confusion". LOGWELL

Read the part about "Why Silver Plating?"

After I took another look at a the wire I had purchased from Surplus Sales, I had to admit that it does not look silver plated. Writing on the insulation is legible: "RUBADUE WIRE CO. INC. #1331 150C 600v... ". The RUBADUE website conveniently lists a product called #1331. spec sheet download

The insulation is not Teflon but is a similar substance listed only as "Flouropolymer". The copper wire is indeed tin plated, not silver like I incorrectly stated.

Teflon is a flouropolymer but not every flourocarbon is Teflon, (eh).

Regardless whether exactly "as advertised" or not, (and regardless whether or not I should eat some "crow") the wire being sold is VERY good quality stuff.
According to the datasheet it is indeed tin plated, with seventeen strands. The insulation is not "the" Teflon but the insulation material has a very low dc (dc = 2.03) and so I believe this wire should be very good for the purposes of making fast coils.

What else is there to say?? Good stuff. GET SOME HERE

[Tinkerer]

There is no doubt that the Teflon wire is superior, it is just much more expensive and hard to get.

Now, looking at the calculator output above, I notice one more interesting thing: the difference in inductance.

Why is it that the PVC wire gives more inductance even if separated by more space?

[gdogg]

hi guys, ive just bought this wire, from aliexpress, it is tin coated copper wire shielded,

and i can tell you its fantastic, the best wire ive bought for coils, ive made a 23cm wide with about 21 turns, and ive used tin solder to wrap it together, it is very sensitive towards gold rings,chains and small pieces, the and gives better response than all the copper ive played with yet to date.. which im using with my surf pi v.2.. dam excellent wire. and the most damdest cheapi you will find on the net..

http://www.aliexpress.com/item/Free-...891963060.html
Free Shipping 300m 0.5mm Orange inner 0.25mm Single strand Copper Wire Tin-plated PVC

[WM6]

http://www.aliexpress.com/item/Free-...891963060.html
Free Shipping 300m 0.5mm Orange inner 0.25mm Single strand Copper Wire Tin-plated PVC

It is not clear how many strands has those wire and if every single strand is isolated (by PVC?)?

[gdogg]

yes isolated, single strand.,.. tested and it works very good

[WM6]

Thanks. How many strands in this cable?

[gdogg]

with the order you should get 2 rolls, each roll is about 150 meters, single strand tin coated copper in pvc

[WM6]

with the order you should get 2 rolls, each roll is about 150 meters, single strand tin coated copper in pvc

There is poor product description and what I am asking is: whether this wire(cable) is single strand wire or multistrand wire?
If wire is multistrand (like Litz wire), then according your explanation single strand of those multistrand wire is PVC isolated?

[gdogg]

as i said, it is single strand..
0.25mm Single strand Copper Wire Tin-plated

meaning that there is only one strand of wire that is tin plated and shielded with pvc (1 wire only) where the litz wire is multi strand but not tin coated, which i have also and from personal experience it doesnt work as good as this wire. I dont know the mathematics, but im straight foward, ill test it, and i only test with gold. cheers,,, i will show a pic of it sometime soon. cheers

[WM6]

as i said, it is single strand..
0.25mm Single strand Copper Wire Tin-plated

meaning that there is only one strand of wire that is tin plated and shielded with pvc (1 wire only) where the litz wire is multi strand but not tin coated, which i have also and from personal experience it doesnt work as good as this wire. I dont know the mathematics, but im straight foward, ill test it, and i only test with gold. cheers,,, i will show a pic of it sometime soon. cheers

Oh I see, thanks. I wrong understand this as: that (every) single strand is tin coated.

Maybe diameter of 0.25mm is a little to small for PI coil, but you say it is working good.

Have you ever tried to build PI coil with speaker connection (multistrand) cable?