Another PI coil shield method.

[6666]

the target used was a uk pound coin, the coil shells used are dons(idx dd type), so i assume 9" round, the barracuda tested was the original anchor spec 9v, my other barracuda(silverdog spec) with the fet and running at 11us(from the pre amp out) running on 12v can detect the pound at 10.5" with the shielded coil, with the unshielded one 11" but the unshielded one is terribly unstable.
though to be fair the two were tested on different days, and the anchor barracuda is non motion, where as the silverdog one is motion, this may effect the results, either way i'd be happy with 10 inches on my favourite beach, as it has remains of a crude oil spill in the hard pack at about those depths and deeper.

Thanks for the info with the pound coin, I now have 2 in my collection will try them next time at the beach.

[6666]

Cut the Scotch 24 mesh 1.18 inches wide. Wrap around the coil but make sure that the wire mesh does not touch and form a cross section shorted section that will cause eddy currents to form.

I wonder if the cross section shorted section is what is causing so many people to have trouble with foil shielding ?

I am thinking maybe a thin copper tape spiral wind around coil but winds not touching ?
http://www.ebay.com.au/itm/New-Arriv...item2333329955

[bbsailor]

I wonder if the cross section shorted section is what is causing so many people to have trouble with foil shielding ?

I am thinking maybe a thin copper tape spiral wind around coil but winds not touching ?
http://www.ebay.com.au/itm/New-Arriv...item2333329955

The ultimate shield test is to make a small, unshielded, fast, test coil to see if various length samples of the shield are detected. Cut a piece 5mm, 10mm, 20mm, 50mm and 100mm long and mount on a piece of cardboard and wave under the coil. The cardboard prevents your hand from being detected on an unshielded coil. Typically, when you want to use delays below about 10us you will need to use a thin coil solid wire or very thin stranded coil wire (about AWG32 stranding). Tinned stranded wire is better than silver coated wire as silver is too conductive between strands and looks more like a small target.

I hope this helps?

Joseph Rogowski

[6666]

Cut a piece 5mm, 10mm, 20mm, 50mm and 100mm long and mount on a piece of cardboard and wave under the coil.

Hi Joseph, I have ordered some of that copper tape and when it arrives will test using your method thanks.

[6666]

I wonder if the cross section shorted section is what is causing so many people to have trouble with foil shielding ?

I am thinking maybe a thin copper tape spiral wind around coil but winds not touching ?
http://www.ebay.com.au/itm/New-Arriv...item2333329955

Just tested a 2 inch or 50mm strip with PI, and not detected, however the WHOLE roll could be.
more to come.

[johnandles]

Just tested a 2 inch or 50mm strip with PI, and not detected, however the WHOLE roll could be.
more to come.

Did you test the amount you you would need to wind around your coil?
I wonder if that would be detected.
Cheers
John

[6666]

Hi John
no have not tested the amount needed to wrap around coil yet, only the 50 mm strip, and whole coil.
this stuff is very thin.

[punagold]

6666,
Have you have success with the copper tape as a shield on your pi coil? I was going to order some when I came across this thread.

[6666]

Hi, no I have not tested the copper foil on a coil yet, maybe in next few weeks, but give it a try your self.