Beach coils: anyone else getting to 31 SENS?

[shrimpygrits]

I got my etrac in 2010 and always used the stock 11" dd coil on the beach here (east coast). My regular running temp is 31 (that's thirty-one, not a typo) using auto+3 with a wide open screen.

Is anyone else able to get to 31? If so, which coil?

There was an ice-cream related incident last weekend and DeeDee didn't make it. The only other coil I have to test with is a giant detech sef, and it won't go much past 20 without complaining.

 

[WormKiller]

I can crank my NEL Sharpshooter up to about 26.... It gets pretty unstable past that due to our highly mineralized soil here in Montucky

 

[shrimpygrits]

I can crank my NEL Sharpshooter up to about 26.... It gets pretty unstable past that due to our highly mineralized soil here in Montucky

26 is my upper bound for inland turf on a good day... normally it's more like 22/23. The beach is a different story - I can put the coil on the ground, noise cancel, and after about 45-60secs it'll start climbing 27, 28, 29... 31 (it skips 30 for some reason).

I'm really trying to figure out it it's this specific coil, any minelab branded coils, or if non-oem coils can hit 31 as well since I'm now in the market for a new one.

 

[WV62]

I am nowhere near a beach but I was doing some testing and in auto sensitivity I was able to get the machine up to 31 by swing high off the ground. So I think your machine is okay. Basically sand has no minerals so it is like me holding the coil off the ground.
But I was looking at the manual last night when I first seen your post and it says you should be running manual sensitivity on the beach.
Now one other fact is there is a difference in depth from auto sensitivity and manual at the same setting.
The 11" DD stock coil will hit a dime out to 11" at manual sensitivity 25, now in auto sensitivity at 25 you will get 9" on the same dime.
Also I have found that the stock 11" coil reaches max depth at manual and auto sensitivity 25, so setting higher will not give you any more depth.

I hope this info help,
Ron in WV

 

[shrimpygrits]

I am nowhere near a beach but I was doing some testing and in auto sensitivity I was able to get the machine up to 31 by swing high off the ground. So I think your machine is okay. Basically sand has no minerals so it is like me holding the coil off the ground.
But I was looking at the manual last night when I first seen your post and it says you should be running manual sensitivity on the beach.
Now one other fact is there is a difference in depth from auto sensitivity and manual at the same setting.
The 11" DD stock coil will hit a dime out to 11" at manual sensitivity 25, now in auto sensitivity at 25 you will get 9" on the same dime.
Also I have found that the stock 11" coil reaches max depth at manual and auto sensitivity 25, so setting higher will not give you any more depth.

I hope this info help,
Ron in WV

Just so I'm clear, in your tests both auto and manual max out at 25, and you're not seeing the dime beyond 9" when auto sensitivity is at 27,28,29... correct? Is the the +1, +2, +3 already factored into that 25 number?

This is super helpful information, thank you. I've been afraid of letting the ghost out of the machine by switching to manual mode and changing the settings that allow me to hit 31. If auto is working with an up front 2" inch handicap on max depth (or whatever ratio) *and* there's no depth increase beyond some fixed auto sensitivity value ~25 (way less than 31 at least), then I'll need to seriously revise my evaluation criteria for the replacement coil. Too bad I can't get back all those hours spent squeezing a few extra points out of balancing :/

 

[WV62]

That would be correct, now that is with the 11" stock DD coil that came with the detector. Now for +1, +2, +3 in auto sensitivity, it was factored in, the machine would not reach those higher sensitivity settings at say A or +1, I had to keep raising my + number until I got the higher numbers I was looking for. So anyway if you can get the machine to run at sensitivity 25 or better you are at max for what auto sensitivity will do.
Now I have other coils like the Sunray 5", the 6x8 butterfly coil and the ultimate 13" coil.
The 5" Sunray coil reaches max depth at sensitivity 26, the 8x6 and the ultimate 13 reach max at 27.
So each coil needs to be tested for max depth at whatever sensitivity.
The auto to manual sensitive depth difference is not the same for all coils. I am going from memory but I think the 5" has 1" difference and the 6x8 was 1.5".

We have all hunted ground with settings less than great, but that is how we learn.
I remember digging a silver half $ once and I told my brother I had no idea what I was digging or why. The force was with me that day.

For me I don't use Auto sensitivity unless I am what we call clad stabbing for items kind of close to the surface down to say 5 inches.

Ron in WV

 

[WV62]

Thought I should correct myself, I checked my charts this morning and I haven't tested the little 6x8 coil in Auto sensitivity and I hadn't tested the 13" coil up in the higher levels of Auto sensitivity.
So here is pictures of my charts and you can see for yourself.
Ron in WV

 

[shrimpygrits]

Thought I should correct myself, I checked my charts this morning and I haven't tested the little 6x8 coil in Auto sensitivity and I hadn't tested the 13" coil up in the higher levels of Auto sensitivity.
So here is pictures of my charts and you can see for yourself.
Ron in WV

View attachment 5417View attachment 5418View attachment 5419

That is an admirable testing methodology you have there - really appreciate the rigor. I probably need to review some theory, as the [detection depth]~[coil diameter] rule of thumb doesn't seem to hold for the smaller coils. I wonder if there is any benefit at all to exceeding these sensitivity ceilings, like smaller object detection or better discrimination, or if the return signal is too diminished to have a noticeable effect. Also curious if the ceilings hold for different conditions(summer/winter, before/after lightning storm) even if the reported values change. I'm usually the 'measure once, cut twice' type, but I think you've convinced me to set up a test garden for benchmarking now. Lots to think about now, thank you.

 

[WV62]

I hate to mess with your test garden but my brothers and I have already went through that several years ago. For starters a fresh buried item will not act like a item that has been in the ground a bunch of years. The ground you put them in may have something near the target buried, that will mess you up. Just way to many variables to get any good out of a test garden.
We gave up on test gardens a long time ago.
As you said the sensitivity has some effect with smaller items, I know that but haven't tested it. I am a coin hunter for the most part and when I was testing I used the smallest coin a dime to see what it does with that. If I can find a dime, I can find the bigger coins. Now I have done some testing on the bigger coins just to get an idea how deep I may hit a bigger coin with different coils.
My rule of thumb is to run the sensitivity as low as I can and still get max depth. The more sensitivity you add the more problems you will have with your detector running stable. It is kind like driving in the fog with your head lights on high beam.
I think the weather and soil conditions effect the performance of the machine, a nice cool day with some good wet ground the machine will for sure go deeper in the ground. The machine is still doing the same thing but conditions let you get good or bad results.
Here is another log sheet for the bigger coins. The numbers at the is the same max sensitivity numbers for each coil that you seen in the other charts. Now just so I don't forget those max sensitivity numbers I took a soldering iron and melted that max number into each coils cover, if I change coils in the field I check and change the sensitivity.

Ron in WV,

 

[Elmy]

I hate to mess with your test garden but my brothers and I have already went through that several years ago. For starters a fresh buried item will not act like a item that has been in the ground a bunch of years. The ground you put them in may have something near the target buried, that will mess you up. Just way to many variables to get any good out of a test garden.
We gave up on test gardens a long time ago.
As you said the sensitivity has some effect with smaller items, I know that but haven't tested it. I am a coin hunter for the most part and when I was testing I used the smallest coin a dime to see what it does with that. If I can find a dime, I can find the bigger coins. Now I have done some testing on the bigger coins just to get an idea how deep I may hit a bigger coin with different coils.
My rule of thumb is to run the sensitivity as low as I can and still get max depth. The more sensitivity you add the more problems you will have with your detector running stable. It is kind like driving in the fog with your head lights on high beam.
I think the weather and soil conditions effect the performance of the machine, a nice cool day with some good wet ground the machine will for sure go deeper in the ground. The machine is still doing the same thing but conditions let you get good or bad results.
Here is another log sheet for the bigger coins. The numbers at the is the same max sensitivity numbers for each coil that you seen in the other charts. Now just so I don't forget those max sensitivity numbers I took a soldering iron and melted that max number into each coils cover, if I change coils in the field I check and change the sensitivity.

Ron in WV,

View attachment 5459

very accurate and greatly detailed explanation wv62 !