17" vs 11" coil - 11" better??

[bklein]

I tried air tests of the 11" vs 17" and found the 11" did better - had a little better depth on US coins and various rings. Neither did very well with gold nuggets (aluminum nuggets hit better).
The 17" was too sensitive to EMI in my front yard - I had to move to the back yard and test both there. So do you think something is wrong with my 17" coil? I bought it used - but it looked like new. Does Minelab have a QA test for coils that would catch the loss in detection depth? I've read others say the 17" is the better coil if you can handle the extra weight.

 

[sprchng]

FBS machines are notoriously crappy at air testing which is why the competitors like to do them so much.
The proof's in the real world.

 

[Overvoltage]

I have all three ML coils for the CTX. I did not get the 17" until about a year after I got the CTX. It has become my primary coil to the point that I have not found a situation where the 6" or the 11" does any better. I even use the 17" in trashy areas and it works great. It did take a while to learn how to pinpoint with it but now I don't even use the pinpoint except for target trace for target identification. I use the wiggle back method for pinpointing.

 

[jerseyjim]

To each his own.I feel the sàme about the 6" coil.It is much easier to swing,and is great in water.I use it more than the 11".

 

[KinTN]

I'm pretty much with Overvoltage. I use my 17 as my primary even in trashy parks. 2 downsides that I see:
1) sucker is Heavy for extended use; pretty much requires a harness for >2 hrs
2) pinpointing on shallower targets (<3") can be tricky- I swear I feel like I am playing whackamole on shallow targets somedays.

The speed at which I can now hunt due to the areal coverage is outstanding.

 

[bklein]

I did some testing and stupidly put the results in another thread - please see the other thread (or i could copy/paste here...)

 

[bklein]

I went back and tried again. I found that the cause may be due to the gain setting. The default originally was Auto +3. Looked like this was resulting in a 23.
If I install the 17" and then bump the Sensitivity to 28 or so the performance is equivalent the 11" at 23. Is this what you guys see?

 

[Drjohn71a]

In my soil, when wet, Auto plus 3 is too sensitive ( on the ground, not from emi), so dropped back to straight Auto. The 17 is the most sens of the CoilTek 10x5, the 11" . At Auto +3, held flat to the ground, it'll pick up my pickup 3 feet away, and a small shovel held 3 1/2 feet overhead, and a sand scoop 2-3 feet from the side.

Pinpointing is off to approaching side right to left, more in shallow. Pinpointing on front edge is "on" right to left, and a bit forward front to back. While the large size seems intimidating, it's such a smooth, controlled,, broad sweeping motion that fits in by giving the computer time to function better than erratic, more rapid sweeping with smaller coils.

It's a bear to handle in thickets, Johnson Grass, heavy brush, so the 11" and 10x5 are great for that. The 10x 5 is fun when crowded because the target location is so fast and natural, and it has pretty good depth for the small coil. And it doesn't catch on tree limbs nor brush like the larger open coils.

In my soil, the depth on the 17" is much superior to the smaller coils.

 

[Drjohn71a]

The confusion in locating targets comes from the fact that you can hear 2,3 or 4 beeps as you move the 17" coil side to side over a target. Slower on center of coil, on shallower targets, gets 4, faster blurs the center two into one so you hear 3. At the tips you hear 2.
BUT, it's easy when making short side to side moves, to be going over a side bar instead of the center bar because the side bar bleep is off to the center on shallow targets.

SO you have to be certain you're on the center bar when you zig-zag. To do this, start slowly, listening for two close beeps or one dropping bleep ( like on the AT Pro when it rolls over a bottle cap).

When you're on the center bar you'll hear "Beep-eep", a strong beep closely followed by a dropping weaker beep as you go side to side. If you've just swung left, you're to the left of the center bar. If you've just swung right, you're to the right of the center bar. Now you just move shortly side to side while backing up until you're on the coil tip where you can easily set the target between those front points.

Hearing only 2 beeps means you're close to the front or back of the coil. Keep in mind that the outside coils beep when shallow target are IN BETWEEN the inner and outer coil bars.

 

[Jason in Enid]

I wish I had some of you people strength! That 17" coil wears me out FAST if I don't have a harness on, so I don't use it except for specific locations and reasons.

 

[trojdor]

I've got two CTX's, and extra coils for each. One of them always has a 17" on it.

In my soil (Colorado), the 17" is (also) much superior in depth to either other coil.
I have no idea what any of the coils do in air tests. When I start hunting coins in the air, I guess I'll find out.

I've been singularly unimpressed with the 11". Perhaps I've got 2 bad examples, but I've got 25 year old detectors that will go as deep or deeper.
I'm supposed to get 'something' from Minelab on Thursday that may include a new 11". If so, it may completely change my mind. We'll see. (I'll post if it does.)

I've found when pinpointing with the 17", to just use the 90 degree trick...pinpoint normally left-right to get a vertical fix, then carefully turn 90 degrees and define/refine the rest of the 'x'.
I find the center will shift up to 3 inches.

Also, when I get multiple shallow/surface coin blips, I'll just raise the coil a foot and scan/pinpoint the 'real' signal. Then just use the pinpointer to recover.

I haven't found the 17" to be "too heavy" for my typical 4 or 5 hour hunts. Noticably heavier, yes. But not 'too heavy'.
You do need to make sure the shaft is short enough so that the detector hangs from your arms, and the coil just misses your toes when swinging.
Otherwise you'd be trying to hold up the coil with your arm muscles, and the coil end has the leverage advantage on you.

I'm not going to need to trade for a Deus anytime soon...I hope.
But then again, I'm only 60...maybe you guys are much older.


HH and Merry Christmas,
mike

 

[KinTN]

...I've found when pinpointing with the 17", to just use the 90 degree trick...pinpoint normally left-right to get a vertical fix, then carefully turn 90 degrees and define/refine the rest of the 'x'.
I find the center will shift up to 3 inches.

Also, when I get multiple shallow/surface coin blips, I'll just raise the coil a foot and scan/pinpoint the 'real' signal. Then just use the pinpointer to recover....

/\ This /\

 

[electricmetal21]

I agree that air testing is not a good test of a coils ability. The conditions in an air test are not the same as in the real world.
In an air test, the detector only has to see through the air between the coil and the target.
But, in the real world, when you're out there detecting, the detector and coil have to see through mineralized ground and discriminate between the target and adjacent trash items.
Detectors and detector coils are not made to see through the air. They're made to see through the ground.