Magnet wire coil

[green]

I'm still trying to use my spool of 28awg magnet wire I purchased probably 40 years ago. I tried a coil today. Don't know what the winding is called. I think I've seen it on the site somewhere. Mostly I've seen spiral, basket and bundled winding. Are there negatives to winding this way? The coil inductance is lower than I was trying for. Including some test data. I had to redo the shield and need to test for shielded resonance and do a little more testing. So far I think it looks alright.

[baum7154]

Very pretty and reminiscent of the old shortwave coils.

Regards,

Dan

[Silver Dollar]

That design doesn't have a name yet. It is a type of basket coil maybe wicker coil?
Or how about vertical zig zag (VZZ for short)?

There is less inductance because of the spacing between windings. Though I made a
basket with the same wire I had made a loose wound coil and it came out to ~ the same
inductance;

[bbsailor]

I'm still trying to use my spool of 28awg magnet wire I purchased probably 40 years ago. I tried a coil today. Don't know what the winding is called. I think I've seen it on the site somewhere. Mostly I've seen spiral, basket and bundled winding. Are there negatives to winding this way? The coil inductance is lower than I was trying for. Including some test data. I had to redo the shield and need to test for shielded resonance and do a little more testing. So far I think it looks alright.

Green,

The ultimate test is to measure the self resonant frequency at the end of the coax you plan to use to incorporate cable capacitance in the resonance reading. Then shield the same coil using the same coax. What I think happens is that the unshielded coil will have a higher resonance than the shielded coil. But, because the area of the coil is spread out to minimize coil turn-to-turn capacitance, and benefit you obtain will be lost when the coil-to-shield capacitance is added. Overall, I find that a 10.5" coil OD inside an 11" housing works well with between 19 and 20 turns. If the wire is thinner with thinner insulation the bundle will be tighter and be at or near 300 uH with 19 turns but if you use a thicker 600V insulation, you will need an additional turn of two to reach 300uH.

bbsailor

[green]

Green,

The ultimate test is to measure the self resonant frequency at the end of the coax you plan to use to incorporate cable capacitance in the resonance reading. Then shield the same coil using the same coax. What I think happens is that the unshielded coil will have a higher resonance than the shielded coil. But, because the area of the coil is spread out to minimize coil turn-to-turn capacitance, and benefit you obtain will be lost when the coil-to-shield capacitance is added. Overall, I find that a 10.5" coil OD inside an 11" housing works well with between 19 and 20 turns. If the wire is thinner with thinner insulation the bundle will be tighter and be at or near 300 uH with 19 turns but if you use a thicker 600V insulation, you will need an additional turn of two to reach 300uH.

bbsailor

Thanks for the reply. As you can see from the photo I have enough wire if I can make the magnet wire work. The shielded coil resonance for the test coil is 2.14 Mhz. Reading "Making a Fast Coil" a 300 uh, 10.5 inch diameter coil made with Teflon coated wire would have a resonance near 1.25 Mhz not shielded and 1 Mhz shielded, coax not connected. Are those good numbers or should the resonances be higher? Think I need to try a 10.5 inch diameter, 300 uh coil and would like resonance numbers to try for.

[bbsailor]

Thanks for the reply. As you can see from the photo I have enough wire if I can make the magnet wire work. The shielded coil resonance for the test coil is 2.14 Mhz. Reading "Making a Fast Coil" a 300 uh, 10.5 inch diameter coil made with Teflon coated wire would have a resonance near 1.25 Mhz not shielded and 1 Mhz shielded, coax not connected. Are those good numbers or should the resonances be higher? Think I need to try a 10.5 inch diameter, 300 uh coil and would like resonance numbers to try for.

Green,

The point I was trying to make is that a total coil capacitance, including shielding, coax MOSFET COSS and other circuit capacitance determines the optimum value of the damping resistor. A higher value of damping resistor means that the total coil circuit is seeing less capacitance and thus has the potential to be faster if the PI circuit can allow for a lower delay setting.

The challenge of your coil design is that while it has a very high self resonant frequency (SRF) unshielded, what is the self resonance with the shield and spacer in place while being measured? The real challenge is to shield your new coil design and try to keep the self resonant frequency (SRF) as high as possible. A wide coil, like you made, will tend to offer more coil area to any shield to your add to your coil and have more coil-to-shield capacitance offsetting the advantage of a high SRF wide coil design . The only way to tell what design is better is to measure the total self resonant frequency and the higher SRF wins as having a potentially lower delay.

Keep on experimenting and post your results and include the coil SRF, damping resistor value and response to lowTime Constant (TC) targets like US nickels, gold rings or gold nuggets. Sampling earlier is mostly beneficial only for low Time Constant (TC) targets

bbsailor

[homefire]

Basket Coil is the name I know them by. Let us know how it does on Small gold. Less then a Gram?

[green]

I did a round and 3-1 coil comparison with a single layer vertical coil, same circumference a while back. Want to try the comparison with the ZZ winding with 3 different shapes with the same circumference. Want to try the 3-1 and DD shape with a Tx and Rx coil for IB. Any guesses or suggestions if it would work?

[green]

20 cm round coil. I'm thinking maybe radial ZZ coil.

[green]

A couple years ago, when I joined the site there was a lot on spiral coils. The coil I'm playing with looks like a spiral coil wound in a zig zag pattern instead of flat. Was the idea for the spiral coil to minimize capacitance, have smaller and larger diameter coils or something else? Maybe it should be a spiral ZZ

[Chet]

Hi Green, your coil is similar to a spiderweb coil which was normally wound on a 9, 11, or 13 slot form which gave it a flat coil appearance. I wound a few of these in my crystal radio days. You wound yours on a 31 pin form then removed the pins. This was then referred to as a diamond weave coil as viewed from the edge it shows the diamond shaped openings. The idea is to reduce the self capacitance by having less paralleled wire surfaces and no form material supporting the winding. Here is an interesting website on old radio coil types;
http://www.pa2mrx.nl/UK/PA2MRX-UK.ht...brewing_uk.htm

[green]

Thanks for the website. Spiderweb coil it is.

[green]

scope picture of 20 cm spiderweb round coil. R damping 1000 ohms

[walkman]

That design doesn't have a name yet. It is a type of basket coil maybe wicker coil?
Or how about vertical zig zag (VZZ for short)?

There is less inductance because of the spacing between windings. Though I made a
basket with the same wire I had made a loose wound coil and it came out to ~ the same
inductance;
[ATTACH]31153[/ATTACH]

Silver Dollar, how to make basketweave coil?

[Silver Dollar]

I followed this guide but used two rows of holes. It should have been enough room but I had to
add some more in a third row to finish the wind;