Making a Mono Coil on the fly

[bklein]

I read a guy express an idea somewhere amongst these threads about making a mono coil by trial and error.
He suggested making the coil somewhat under the calculator-suggested number of turns and leaving enough extra wire so that he could wind a turn and check performance - wind a turn, check performance - etc. Has anyone done this for a coil for a Minelab (I have a GP Extreme). I bought a bunch of Litz wire sometime back and wonder if I should give this a try - but what should I look for? Better range - smaller target detection? Or does this process add so much capacitance that it is a bad way to go? When I tested an original Minelab coax, it had the most capacitance per foot against USB 3.0 cable/Esata cable/and a coax cable I had. So I'm thinking perhaps it may be worth a shot.
I'm planning on trying to make an 18" first, then maybe 6". My Litz is pretty thick stuff - 100 strands I think.

[IBGold]

Hi I often wind this way I work out roughly what turns I should need wind one less check then check each turn until I get what I want the trick is no metal in the coil winder and the inductance will rise slightly when you lace the coil or put spiral wrap on it is easy with tinned wire as you can make a lead for the LCR meter with a pin as its connection and push it through the insulation to get the reading but with Litz you have to prepare the ends and what is not wound on the winder has to be laid out with no loops to get the inductance reading with your wire for Minelab PI coils you need roughly 17AWG wire for an 18" mono I would use 36/.2mm Litz or equivalent this will at 300uh give you a finished coil with .4 ohms resistance which is ultimately what you are looking for.

Regards, Ian.

[bklein]

Thanks for the help.
Any recommended sources for this wire in the US?

[bklein]

To confirm, .2mm = 32AWG correct? Some charts list mm's in area too which is a different AWG equivalent.
Do you use served wire (silk covering)?
Here is one I'm considering: http://www.ebay.com/sch/i.html?_trks...at=0&_from=R40

[IBGold]

Correct and yes to the second when hand making the 36/.2 Stefan uses a yellow tape that I think he obtains from R.S.Components which seems to work well as far as sources in the US you could try Razorback coils he had some 34/.2 with Teflon serving will have slightly more resistance that I would like, I usually look on EBay the 660/46 is OK for small coils but not enough area for an 18' coil keep your eye out something will turn up most of the Litz I have used has come from the US.

As for coax I use Soundlink audio coax the red/purple one 7mm diam it is low capacitance and works for me have fun.

Regards, Ian.

[bklein]

The wire in the ebay link may only come in 50' spools. Is it noticeable when you splice two lengths? Calculations seem to indicate 89.5' necessary.
The Soundlink stuff seems difficult to find (so far) here in the states. (searched on Soundlink 7mm audio coax). Mainly AU hits.

[IBGold]

Hi the coax is made in the US I will try and find out a bit more for you as for the Litz I usually buy more than 50 feet at a time buy two spools and ask them to supply it in a continuous 100 foot length I have never had a problem with sellers doing that it saves them a spool.

Regards, Ian.

[bklein]

Here are his specs on his 32/33 Litz wire:
Top quality Litz Type 1 stranded wire
18AWG Size
Sold by 50 foot section for your application more available by the foot at .75 cents per foot
32/33 equals total of 32 strands of 33 AWG wire
The strands are individually coated (Litz patent)
Circ Mil 1613
Nominal OD .054
5.24 lbs to 1000 feet
6.72 ohms in 1000 feet
32 strands
This seems to work out to around .6 ohms for 90 feet. Too high, huh.
He sells 660/46 as well (I'll ask for specs) - at what coil diameter do you switch over to using this wire? I'd like to make a 6" eliptical too. I bought an 8" housing but later bought an 8" mono coil that works fine so what's the point there... I mainly want to start with the 18", then 6" eliptical, and maybe an 11" later on.

[IBGold]

Here are his specs on his 32/33 Litz wire:
Top quality Litz Type 1 stranded wire
18AWG Size
Sold by 50 foot section for your application more available by the foot at .75 cents per foot
32/33 equals total of 32 strands of 33 AWG wire
The strands are individually coated (Litz patent)
Circ Mil 1613
Nominal OD .054
5.24 lbs to 1000 feet
6.72 ohms in 1000 feet
32 strands
This seems to work out to around .6 ohms for 90 feet. Too high, huh.
He sells 660/46 as well (I'll ask for specs) - at what coil diameter do you switch over to using this wire? I'd like to make a 6" eliptical too. I bought an 8" housing but later bought an 8" mono coil that works fine so what's the point there... I mainly want to start with the 18", then 6" eliptical, and maybe an 11" later on.

It has not enough strands for an 18" coil you need 36/.2 or equivalent =17AWG, for the smaller coils and maybe the 11" the 660/46 should do fine with the 6" if the resistance is too low you can cut a strand at a time on the shield end of the coil until you achieve the correct resistance.

Regards, Ian.

[bklein]

It has not enough strands for an 18" coil you need 36/.2 or equivalent =17AWG, for the smaller coils and maybe the 11" the 660/46 should do fine with the 6" if the resistance is too low you can cut a strand at a time on the shield end of the coil until you achieve the correct resistance.

Regards, Ian.

Obvious solution but I wouldn't have thought of it until you suggested it.
Soundlink is a mysterious manufacturer/brand. I can't find anything on it for a manufacturing headquarters. Seems the brand is common in Australia but nowhere else.

[g.s]

Hello from G.S Someone IS BUILT HERE coil for sd2000 minelab.I read about wires litz and teflon wire can explain please what wire is suitable for 300mm coil 300uh self-induction 0.4 ohm resistance.I want to buy from ebay but there are too many,is the proper code
to build mono coil THANK beforehand..