Concentric coil V shallow targets

[ExpIInut]

This little item was found as is, in 2 parts about 3 feet apart - it's 30mm long and silver - now my question is this why were a lot of my shallow targets giving mixed ferrous/non ferrous signals and not locking on? anything over 2 inches was no problem, a good solid dig /don't dig signal - this was only bought to my attention after spotting a little pewter button on the surface and it wouldn't lock on - after that I had to check all mixed tones - I'm sure I never had this problem when I was running an SEF on my last MXT - any ideas?

 

[Aarong81]

I would think that pewter button would be a nasty iffy signal at any depth. Did you try testing the button at different depths from the coil to see what VDI's it gave on screen?

You didn't mention the coil your currently using or the gain setting. One problem I have noticed even with the 950 is that the center of the cone signal very close to the coil has a blind spot. Its only very close to the coil that this happens, as in touching or nearly touching the coil, with the 950 it would be in the center of a hole in the coil so obviously it wouldn't actually touch. I would imagine that this affect would be exaggerated with a larger coil such as the super 12"(300mm) coil. I really doubt this would be an issue with the 5.3 as it works great with even tiny targets right up against the coil, plus smaller coils are more accurate with target ID than larger coils.

I am currently using the D2 coil and it does not have that issue. Targets touching the coil are extremely noticed as the signal is highly concentrated in such a narrow strip along the center of the coil. Although I have noticed surface finds can show up as 3 different spots with the D2, the center loudest 'target' being the true location. I have found some targets that looked like 3 targets and once the center loudest one was removed the outer weaker targets were gone. Thats only an issue with specifically SURFACE targets.

 

[ExpIInut]

Std 950 coil - Relic - zero disc - trigger forward - tracking unlocked on this particular occasion - however I've been out again tonight in the same field and had the same problem no matter what I did, only this time the machine was registering "coke" (spent fuel) as a good signal with a high reading. When I had an MXT before this never happened this type of target ALWAYS hit at 0 on the screen, but then again I was using an SEF coil - beats me!

 

[Aarong81]

I have no idea what "coke" (spent fuel) is, Your not referring to hotrock are you? Hotrock is at the bottom most of the vdi scale and you referenced 0 VDI on your old mxt.

 

[ExpIInut]

I'm in the UK - we've got hot rocks also, they usually register 95 - "coke" is burnt coal and is a pain, some machines ignore it, some like the MXT register it with a confident 0 or 2 at the highest but with this coil it's been coming in at 20+ - am going to buy another coil to double check - just in case.

 

[Aarong81]

Is this 'coke' target just giving you that problem in a certain area or is it a widespread problem everywhere? It could be a target you have not encountered until now and only similar to the 'coke' type target.

 

[ExpIInut]

You will find "coke" in a lot of fields in the UK - the site I'm on at the moment is only available due to crop failure, and the farmer has sprayed it off to sow with grass instead - am off out again now to try, only this time I'm going to disc out a small iron nail and see if that improves the situation.

 

[Aarong81]

How can you detect with your disc at zero anyways? Even if your wanting to see some iron you can disc everything below, say, -10. I disc everything below +15 so I still dig nickels and pull-tabs, that makes for ALOT of holes to dig without seeing all the iron too.

 

[ExpIInut]

I use the tones to discriminate - I never dig any iron