Coil Question - difference in depth between 11" & 17"

[metaldiggr]

I'm a little over a one year owner of the CTX. I moved from the AT Pro to the CTX last year and love it.

I've been noticing that I typically find things at 6" or less. I've been hunting really old parks and know that there's a good bit of stuff way down. If I pick an area and move really slow hitting it from different directions and using the pinpointer to draw on the screen I can find deeper stuff. I decided to redo my back yard and bury various silver dimes and quarters at different depths. Over the last month since burying the coins I've learned a lot of finding deep stuff. I've noticed that I don't get a solid lock on my 8" & 9" quarters. I get a bunch of random info that ranges from 12.25'ish to 12:45'ish, what I typically wouldn't dig. This is all using the 11" coil. I bought the 17" last year thinking that it would give me a little more depth but using it in the yard shows no difference. I get exactly the same response as if I had the 11" on. I've seen a bunch of videos of guys hitting deep silver and question my lack of hitting an 8" silver quarter. The 17 not making any difference has me thinking I could of saved the $400. Or, is there something in my machine that's not right. I know there's a lot of variable that could make the difference in depth, should the 17" coil make a difference?

 

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[Terry Soloman]

You need to learn your set ups better. You can open that machine up and it's deeper than the E-trac. Find a dealer or user and get some advice on your programming

https://www.google.com/search?rlz=1...1CmGFjQSmDUfGgAcAJ4AIABhwGIAZAHkgEEMTEuMZgBAK

 

[SD51]

Agree with Terry, also, what sensitivity are you running at in your test garden? Auto or manual?

 

[metaldiggr]

You need to learn your set ups better. You can open that machine up and it's deeper than the E-trac. Find a dealer or user and get some advice on your programming

https://www.google.com/search?rlz=1...1CmGFjQSmDUfGgAcAJ4AIABhwGIAZAHkgEEMTEuMZgBAK

I think 8" should be hitable but I'm not new to the hobby. I've tried a lot of setting changes and don't see much difference in any, this is why I'm posting here... I'm out of ideas and thinking it's hardware related.

Agree with Terry, also, what sensitivity are you running at in your test garden? Auto or manual?

I've run every setting option on both coils, from "auto" 0 to +3 & manual from 15 to 30. My AT Pro hits the 8" quarter better. I've run ML's stock programs and my silver and coins as well.

 

[signal_line]

The thing with big coils is in mineralized ground they see more ground and that means you probably need to turn down the sensitivity. So now you haven't gained much. In clean ground you can get some added depth but not much on small targets. Big coils are hard to swing and to get into tight spots. Minelab coils are heavy to start with.

 

[metaldiggr]

The thing with big coils is in mineralized ground they see more ground and that means you probably need to turn down the sensitivity. So now you haven't gained much. In clean ground you can get some added depth but not much on small targets. Big coils are hard to swing and to get into tight spots. Minelab coils are heavy to start with.

I haven't had many issues with mineralization using the big coil. I spend a lot of time in the woods away from interference and the soil here's not too bad. It is heavy! I didn't detect for about 5 months, took it out once with the 11" coil then swapped the 17" on for the second time out... my arm was spent after an hour. Fortunately, it built up pretty fast and I can use it now without any problems.

I've been detecting for a little over 12 years. I did well with the AT Pro, did my due-diligence with learning the ins and outs. This one's got me stumped, there's no difference in coils and my 8" silver quarter hits on the ATP.

 

[MidMoTreasure]

What are your settings? Fast on or off? Deep on or off? What target separation are you using? What is your dirt like? I have no problem hitting 8"-9" silver dimes here in my Mid-Missouri dirt. I have best results running Fast Off, Deep On, and Low Trash separation (14" deep Civil War bullets). Fast On tends to decrease depth as does High Trash separation. I don't notice much depth loss with Ferrous-Coin. I haven't had much experience with Ground-Coin because the places I use it (Southern Missouri) have shallow targets.

I agree with you that the 17" coil is no deeper than the 11" coil. I have experienced the same results in my 8+ years with the machine. I like the 17" for the extra ground coverage.

 

[PowerDubs]

I’ve found silver quarters way deeper with my At Pro than either my CTX or my equinox. Go figure.

 

[Gold Maven]

keep in mind too, that your detection area under a round coil comes to a point, so you must overlap your swings to thoroughly search at maximum depth.

 

[gunsil]

keep in mind too, that your detection area under a round coil comes to a point, so you must overlap your swings to thoroughly search at maximum depth.

This is not true. It is only true for concentric coils which are not used much anymore. The coils on the OP's CTX are DD coils and the detection area does not come to a point like an inverted cone as with concentric coils. One does need a little overlap with DD coils, but nowhere near as much as with a concentric coil. It also doesn't matter if a coil is round or elliptical, if it is a DD coil the detection depth is the same the full width of the coil except at the very outer edges. Your Tesoro likely has a concentric coil but it is a detector with ancient design. Not that it isn't a good detector, it is, but the modern DD coils are better in most situations.

 

[cudamark]

When you get jumping I.D. numbers, I always look at the depth meter. If it's deep, I dig, if it's shallow, it's probably junk. I.D. numbers on most machines get very sketchy after 7-8 inches or so of depth. At old sites, I don't pay much attention to what number the target is, but, instead I go by the depth.

 

[metaldiggr]

I emailed Minelab and described the issue, a day or so later they sent a RMA number and address to send it. On the 1-month day that I sent it in I got an email stating that they can't get my ctx to ground balance. They swapped the coils with their test unit first and both of my coils balanced fine. They swapped the Interface PCB and the issue followed to the test unit. They installed a new Interface PCB and shipped it back. I found 2 V-nickels, 1 buffalo and a Merc yesterday.

It had nothing to do with "my setups".