8" BasketWeave Litz Coil.

[ericwd9]

Here are pix of an 8" Basket Weave Coil.
30 turns of 1.5mm Litz (have no Idea of its configuration)
Inductance 190uH
Self resonance 790KHz
Set up with Stuart PI II Revisited.
Close wound magnet wire 30T 1g gold 50mm
This coil 1g gold 80mm
Pulse width 30uS
Delay 8uS
Sample width 10uS
Damping 470 OHMS (not optomised.)



Eric

[baum7154]

Here are pix of an 8" Basket Weave Coil.
30 turns of 1.5mm Litz (have no Idea of its configuration)
Inductance 190uH
Self resonance 790KHz
Set up with Stuart PI II Revisited.
Close wound magnet wire 30T 1g gold 50mm
This coil 1g gold 80mm
Pulse width 30uS
Delay 8uS
Sample width 10uS
Damping 470 OHMS (not optomised.)

[ATTACH]33096[/ATTACH][ATTACH]33097[/ATTACH]

Eric

----------
Did you wind this coil Eric? Nice work.

30 turns on a coil like this should yield more than 300 uh so I am surprised it is only 190 uh!

1.5 mm (0.060") is very large wire for a coil. Is that measurement including the insulation?

How many ohms does the coil measure?

Does this coil see your hand when you grasp it? If so, reverse the coil leads at the detector to get the self shielding right and see if it detects your hand grasp. With the outermost winding end at system ground it should not detect your hand.

If you have not already done so take a look at the Chance PI Coil thread in this same forum for other coils of this type.

Regards,

Dan

[ericwd9]

Yes I wound it today.
Inductance was measured with a Chinese LRC hand held meter.
Measurement includes wrapped coating.
A 30 turn magnet wire loose wrapped 8in coil measures 360uH on same meter.
Ohms = 1.2
Self shielding is in evidence.
I am confused as to why the inductance is so much lower than the magnet wire???
Field collapses rapidly with this coil and delay can be set sooner for receive sample.
I live in South Australia and I have reported this here as my intellectual property given to the public domain.
This may prevent future patenting of a similar design and facilitate others to contribute.
I am an elderly man. I used coils of this design for MF reception in my childhood.
The high "Q" enabled good reception without gain.
The tubular construction should enable coating with polyester glass after sealing to retain air.
I would entertain suggestions for the seal?
I contemplate wrapping with glass tape and then PVC tape???
Best regards to all who experiment with the true scientific principals.
Chance threads were the genesis of this coil along with my childhood memories and their scientific explanation.
Eric

[baum7154]

Running the math on your damping resistor value PI x SRF (MHz) x inductance (uh) gives 471.55 ohms so you are right in the ball park with your 470 ohm damping. I don't know the true SRF with feed line and detector capacitances in place so it could be a bit lower damping value I suppose.

Dan

[baum7154]

The tubular construction should enable coating with polyester glass after sealing to retain air.
I would entertain suggestions for the seal?
I contemplate wrapping with glass tape and then PVC tape???
Best regards to all who experiment with the true scientific principals.
Chance threads were the genesis of this coil along with my childhood memories and their scientific explanation.
Eric[/QUOTE]
----------

Eric, I am in the process of documenting the fiberglass coating of my latest spider wound 4x12.5" coil of this type in the Chance PI Coil thread. At this point the coil is over wrapped with self adhesive cloth hospital tape and I am now patterning the first of two polyester fiberglass layers. I have done this several times in the past 4 years and some of my pictures of 8" round coils are posted I believe on pages 2 or 3 of that thread. Will finish the documentation with photos of the 4 x 12.5" very soon. Please take a look at the profiling pictures of the coil using PE foam.

Regards,

Dan

[ericwd9]

I am not too shure of the reason the inductance of the Litz coil is less than that of the magnet wire one, yet the self resonant frequency is lower??? The bulk of the litz wire makes for a larger overall cross section of wire and coil. I have coated the coil with two dry layers of fine glass tape then one of PVC to seal in air. This has been polyester glassed over. No further testing at this stage. Litz wire was well known in my early years for use at VLF. There has been a lot of missinformation disseminated concerning this wire. Its primary use is to reduce loss and increase Q (efficiency) at low frequencies. In terms of actual magnetic flux, inductance of the coil is irrevelant but in terms of speed of the collapse of that field then the higher the resonant frequency the faster the colapse and recovery. However a higher inductance will provide greater sensitivity as a reciever. It has been said by many that the recieve coil (where separate should be the same in characteristics to the transmitt coil. I contest this and say that the recieve coil can be more turns but needs to be better shielded. Also so called litz wire?
True Litz wire has conductors in numbers that are powers of 3, so you have 3, 9, 27, 81, 243 etc strands. Each strand makes its way from the centre of the bunch to the outside and back again over a certain length of wire, and this repeats. Which is why true Litz wire is expensive.

Bunched conductors are just that - a number of fine insulated conductors served originally with single or double cotton or single or double silk. These days, self fluxing conductors and an artificial serving (acetal?) so you just solder to the stuff.

This area needs more reasearch. A target responce is that of a colapsing magnetic field induced by the eddy currents in the target. The slope of the colapse is frequency related and is relative to the size and internal resistance of the target material. The resonant frequency of the recieve coil could well provide some discrimination of the material type.
Eric