6" 18.75kHz DD coil question :shrug:

[Treasure Nut]

Last week I managed to add a new 6" high frequency coil for my X-Terra 50. I got some use out of it. Got a question though.

I was under the assumption that the DD coil makes a thin blade like signal in the centre of the coil, from the front of the coil to the back. Like Nero's pic shows.

Had a lot of trouble using it in a trashy area, so I took it home and air tested it with a couple dimes, an earing, and a small piece of aluminum also about the size of a dime. Swinging the coil about 1 to 2 inches over the targets I get 2 beeps (one on each side of the coil) in one pass on the outer edges of the coil. I'm finding it difficult to pinpoint targets in the 1 to 2 inch range. I purchased this coil to help me separate targets, not make double beeps on them in shallow depths.

Is this normal? Any help would be appreciated.

 

[BarnacleBill]

Normal for many coils on shallow targets, simply lift the coil, while shortening your swing down to a wiggle.

HH
BarnacleBill

 

[Treasure Nut]

OK, but I didn't think I would get this with a smaller coil.

Thanks

 

[nero_design]

It should be very sharp on surface targets and a bit softer with those targets found at depth.
I spent a while experimenting with the coils on my X-Terra 70 before rendering that image... the "blade" region is quite sharply defined on the
6" HF DD coil although it gets a little more tricky with targets closer to the surface:

See the green glow in the illustration? That's what I refer to as a 'secondary field' because it's very sensitive too. If a target it close to the surface, it may be
close enough to trigger the coil by being in the secondary field or the primary emission blade. Pinpointing should still work well though.
This is a particularly sensitive coil. Instead of a large bleeeeeeeep (like the elliptical coil gives), the smaller 6" coil gives a fairly assertive BLIP! when the target passes under the main detection field. The fields actually have more of a 'layered' look to them but I haven't quite figured a way to show this beyond the illustrations I did earlier.

Cheers,

Marco

 

[khouse]

I get double beeps on surface targets with my 4.5 inch coil. (Yellow machine) Like it has been said. If you get a double beep raise the coil. If you still get a double beep then there may be two targets there. Today I was hunting a sand VB court with my 10.5 inch ddhf coil. I got a double beep. I didn't raise my coil being on the sand. I simply scooped in the center of the beeps. 2 scoops and out pops a 2007 Washington dollar coin. I love the sand!