coil shielding

[Luuk]

I built a coil for my bara. 9" circular bundle wound. .55 multistrand hook up wire. 440uH normally I use graphite powder for the shields but decided to try something different this time round. I unwound 6 turns from the coil and turned the wire in a long spiral around the coil bundle and completed 4 spiral turns. the spirals turned out to be approx 8 - 10mm apart. Taped up the entire coil bundle and fitted it into the coil housing and completed the coil. I took it down to the beach today to test on the wet sand, black sand and in the water and lo and behold, no falsing at all, and the depth of detection is excellent. my electronics knowledge is pretty limited so I don't know if this is 'normal' or if i am just lucky

[Qiaozhi]

What is your sample delay set to?

[Luuk]

I do not have an oscilloscope so I have no idea what the sample delay is

[6666]

but decided to try something different this time round

Interesting , that experiment is on my list of things to try, when you made the 4 wraps did you over lap them ?

[Luuk]

the 4 wraps did not over lap each other

[6666]

How did you wind it if they dont over lap, ? thanks

[jladre]

Can you post some photos of it so that we could have an idea what you did?

[Luuk]

I am away this week, will post photo when I get back

[Luuk]

coil shielding

this is a photo of a similar coil but not the original coil which was enclosed without a photo being taken

[jladre]

Good idea Luuk.. i will try this one soon.. ..

[6666]

Thanks for the photo Luuk, does this coil have 4 wraps ?

[Luuk]

Yes, there are 4 wraps spiraled around the coil. it will be interesting to see if you get the same results

[Koala]

Slightly different but Eric Foster use to use this method. Hard to tell the effectiveness of the shield on the Baracuda as it runs pretty quite without a shield at all.

[dfbowers]

I have seen something similar as well in Charles D. Rakes publications a long time ago. Apparently, a simple Faraday cage can be somewhat effective in some applications.
Is the "end" of your spiral wrap connected to ground?

[Luuk]

I have seen something similar as well in Charles D. Rakes publications a long time ago. Apparently, a simple Faraday cage can be somewhat effective in some applications.
Is the "end" of your spiral wrap connected to ground?

that is correct. the end of the spiral is connected to ground