Coil Expert Advice

[jvanostrand]

Hi All,

I'm looking for lost blocks of lead underwater in deep silt and I'd like to know what coil characteristics would be best for that.

The block are expected to be between fist sized (3 lbs/1.5 kg) and brick sized (8 lbs/4 kg) and are expected to be 8 to 16 inches deep in silt and weed. The coil will be attached to a Surf Pi from Silverdog. I tried 24awg speaker wire (7" ID, 29 turns) and I'm only able to get about 8 inches at best.

Would a larger diameter coil be better? One will less resistance? More winds? Is a higher voltage something worth trying?

[ivconic]

Hi All,

I'm looking for lost blocks of lead underwater in deep silt and I'd like to know what coil characteristics would be best for that.

The block are expected to be between fist sized (3 lbs/1.5 kg) and brick sized (8 lbs/4 kg) and are expected to be 8 to 16 inches deep in silt and weed. The coil will be attached to a Surf Pi from Silverdog. I tried 24awg speaker wire (7" ID, 29 turns) and I'm only able to get about 8 inches at best.

Would a larger diameter coil be better? One will less resistance? More winds? Is a higher voltage something worth trying?

Toss damn SurfPI and use something more serious!
SurfPi is not capable enough.
...or try with some large diameter coil...

[Davor]

I think Surf would do just fine even with a modest coil against such big targets. A bigger coil should do better.
I often find larger chunks of lead at beaches, and it always gives massive signal. It is not alloyed, and hence its conductivity is very good.

[Monolith]

Hi All,

I'm looking for lost blocks of lead underwater in deep silt and I'd like to know what coil characteristics would be best for that.

The block are expected to be between fist sized (3 lbs/1.5 kg) and brick sized (8 lbs/4 kg) and are expected to be 8 to 16 inches deep in silt and weed. The coil will be attached to a Surf Pi from Silverdog. I tried 24awg speaker wire (7" ID, 29 turns) and I'm only able to get about 8 inches at best.

Would a larger diameter coil be better? One will less resistance? More winds? Is a higher voltage something worth trying?

Make a coil of 16" diameter and 17 turns. This will find your lead.

[Koala]

and I'm only able to get about 8 inches at best.

I haven't built the SurfPI but built the Barracuda and would have expected twice that even with a 8" coil on such a large target. Are you sure its working properly. Having said that I have never tested under salt water.

[Ferric Toes]

I have a 4lb divers lead weight and using an 11in diameter coil, I can get 22in for a repeatable signal using a Vallon mine detector.

[Sean_Goddard]

I tried 24awg speaker wire (7" ID, 29 turns) and I'm only able to get about 8 inches at best.

on WHAT target???

Use 10.5" former with 22 turns of 16AWG. I get 12" in air on a UK 10p and about the same in ground. You MUST tune the sample delay to your coil to get best sensitivity.

Nothing wrong with the Silverdog Surf PI kit. Mine worked first time and gave excellent performance (much better than than the CS 4PI). Tweaking the second pulse to about 162us instead of 150us makes a big difference too.

Hi Eric BTW, good to see you active again, I was beginning to worry that the rumours of your demise were true. Thank God they are not. Peace!

[Koala]

If I read it right its 8" on a 1lb of lead ???