More experimenting with Magnetic Hot Rock.:smile:

[BarnacleBill]

From time to time when I get a couple new detectors I test them against the Magnetic Hot Rock which I use as my own personal piece of bad ground. The procedure is pretty simple, find a piece of clean ground, put the Hot Rock down & GB to it, then place a coin under the rock to see if a detector will give a positive indication. Tonite I used a clad quarter which is a pretty easy target.


The Rock:

[attachment 123571 Hrock1.jpg]


Machines tested:

1. Fisher Edge w/ 8 inch concentric. This is the control machine as I've tested it before.
2. Fisher F70 w/ stock concentric coil.
3. X-Terra X705 w/ HF concentric, LF concentric, HF 6 inch DD.

1A. The Fisher Edge, Sens=7, Disc=0. ID'd coin under rock as -36, big iron. Muted audio.

2A. Fisher F70, Sens=70, Disc=15, DE mode, GB'd @ 88, Fe Scale=Full Meter No ID, muted audio.

3A. X-Terra X705 C&T mode, Sens=22, Auto N/C, Auto GB, Pattern 1 & All Metal tested.
a. HF Concentric GB=9, ID=(-)8.
b. LF concentric GB=5, ID=(-)8
c. 6 inch HF DD GB=11, ID=(-)8

Tested the mineralisation level with the X705, Hot Rock came in @ 260,000 Therefore the F70 Fe Scale Full reads 260,000 or less on the X705. There are places I hunt that are in the 400,000 range.

I also noted that the Edge & F70 could never quite get a precise GB. Therefore there was some slight reaction still to the Hot Rock, whereas the X705 could achieve a very precise GB.

So once again the Coin mode detectors cannot see the quarter under this ~3 inch thick rock as a good target. But put the X705 in Prospecting mode and it's a whole different ball game. Even with Iron Mask at 20 the quarter is loud and clear.

HH
BarnacleBill

 

[steve herschbach]

Hi Bill,

It is always disappointing the difference I see between a disc mode and an all metal mode in high mineral ground. The X-Terra is a prime example. OK in Coin Mode, knock your socks off in Prospecting Mode. It just shows how many good targets are still waiting out there. If only we could get good target id to all metal depths it would be a brand new game.

Steve Herschbach

 

[BarnacleBill]

I do wonder if an Expanded range of the Iron Mask might be of some use. I saw one of the Software types on the V forum talking about the two frequency subtraction method for Saltwater which is conductive. Thinking about that, I also wonder if the same technique could be applied to the magnetic portion of the scale. In this case I would GB over the rock and the response be subtracted out using two frequencies. Somebody should send me a V for extensive testing on my rock.

Or the old Naughty trick could be helpful, AM in one ear & Disc in the other. In the case of the Terra line, Prospecting AM in one ear, Disc in the other. Because it does appear that since the rock is canceled out via GB, then the -8 iron response is in reality a composite signal of silver ~44 mixed with the iron in the rock, which pulls the ID down to -8.

I wish the metal detector designers would quite goofing off and get to work.

HH
BarnacleBill

 

[Steve in Idaho]

In areas that are not high trash areas, I hunt in prospect mode and switch back to coin mode to get an ID. I can ID targets that are deep (12" plus on a silver $) with this method and would not work with the big W detector that I was using before the X-70.

 

[Keith Southern]

n/t

 

[OzarkTom]

We have some bad ground here in my home town. Throw a coin on top of the ground, and it is lost to all detectors.

 

[BarnacleBill]

Tom,

Have you tried the Prospecting mode over that bad ground? As long as it is not causing the detector to go into overload, you might be able to pull out some items that have been missed.

HH
BarnacleBill