Question on masking with 3x18 coil

[tvr]

I have been thinking about getting a 3 x18. I was wondering if anyone has tried to see if there is masking by discriminated out iron when over a coin in the same part of the swing path? Like the diagram ... and how about at 90 degrees?
Any experience with uMax or HOT in this scenario is appreciated!
tvr

 

[jabbo]

TVR, just tested my 3x18 with a bent small nail ( U shaped) and a silver dime. Spaced 3 inches apart and with nail raised 1.5 inches higher on a wood block. Everything was on top of a cardboard box. Had to drop coil to about 4 inches above the dime. Got a single short beep before the coil tip reached the nail, then no signal. I turned 90 degrees and got a one way signal with each sweep. In both stances there was a reduced detectable depth because of the nail. Best way seems to be when the side of the coil approaches the coin first, then there is a short beep, but only a one way beep.

 

[nad]

OK,Dave now you tell me.. Have to go back and see what those ignored single beeps were..right now, trying to get the artifacts identified I found at the Battle Of Killdeer in No Dak...If my hunch is right, Lee Franzen and I stumbled across the site where the two trooper were killed.on picket duty.Am going to finish a write up and send it off to one of the magazines..I had a guy in Georgia that said he would take a stab at the items identity, but lost him..Got turned down at two interesting spots, Getting the big cheese in a museum to go in and ask for me.That fails, we'll hope the old "outlive em" ploy works a second time.Thanks TVR ,and you, for bringing up masking, with this coil,, was something I had not thought about.Nad

 

[jabbo]

Larry, in the test, I noticed that when the coil gets close to the iron nail it interferes with the coin signal, just as with any other coil. In my test the nail was about 1.5 inches higher (closer to the coil) than the silver dime. If they were at the same level then the coin would have come through better. Dave

 

[tvr]

Jabbo,
Thanks for taking the time to set up the tests! Really appreciate it!!! 4 inches deep will still find a lot of things given the larger sweep coverage of the 3 x 18. At 4 inches down, the 9 x 8 concentric is probably covering between 5 and 6 inches front to back in good conditions.

I wasn't sure what would happen with them inline with the length of the coil but kind of expected the coin would beep if hit first at the 90 degree way. Sounds better than encouraging with the results you got.

I think I will put one of these coils (in HOT version) on the birthday list if I don't just pick one up before then.

Nad,
Hope you get permission on those two interesting spots and please give us some hints on the magazine when you reach print. I'm interested in reading about it!
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