Hit local lake with Legend

[TheFrood]

Hit the local lake for about an hour-ish after work yesterday.
When I was hunting the dry sand using field mode there were no issues, but when I got the coil about 4" or
deeper under the water there was essentially a massive spike in EMI... Had to turn the sensitivity down to
around 15 to get the signals to something even remotely usable. Go back on the dry, can turn the sensitivity
back up to 25 or so without issue.

Unfortunately no finds worth mentioning. Added about 35 bottle caps to my collection and found one little
round magnet 2 pulltabs, and 3 more bottle caps when hunting in the water. The rest of the bottle caps and
quite a few more pulltabs were all found above the waterline.

 

[Diga]

Unless there is somehow active electrical lines under the water, the cause of that isn't EMI

If it's a salt lake, then you should be using Beach mode's MW in the water.

 

[TheFrood]

Fresh water. Was using field mode, multi 1 (not sure what specifically Multi 1, 2, 3 do...) 4 swing speed, 8 IF, 60 tones
threshold 1. Numbers bouncing all over with the slightest movement of the coil even if it's not near the lake bottom.

Thought it may have something to do with the movement of the water. Ground balancing while under water helped
a little.

 

[jmaclen]

I can only speak from my experiences when something like you describe happens in a freshwater situation. They may not apply to you at all.

Coil and coil cable bump. The entire coil and much of the cable is encountering a lot of resistance when submerged. I have to make sure that my coil cable is secured to the shaft very well and that it's not flopping around near the coil which will detect it. I have to swing the coil more gently, slowly and with smooth transitions especially at higher sensitivity. Swinging a coil in water is like swinging a coil in thick mud or brush where the coil is constantly making contact with something other than air. Higher sensitivity levels will make things worse. So can water with lots of current or directional flow.

Ground balance, sensitivity, recovery speed, search mode or frequency change. The changes in mineral levels including low levels of fertilizer, salt and iron between dry to wet sand to submerged sand and suspended in the water can make a detector sound off and get noisy. Adjusting those settings may help. I detect at one lake here in Colorado where changing from Field M1 or M2 to Field M3 when transitioning into the water without making any other adjustments, makes a big difference. If you hear an immediate change in noise levels just by gently submerging (not swinging) the coil in freshwater, you may need to make a settings adjustment.

Some of the lakes in my area have aeration pumps that are run by underwater 220v electrical cables. My detectors will definitely pick up EMI interference from those cables when I get close to them, even when they are underwater.

 

[Big Boys Hobbies]

Good info here. My first guess was a loose cable too. Water moving in around will definitely make things noisy.

 

[Diga]

No salt and probably not emi...my guess would be other types of mineralization in the ground from the wet to dry transition. Especially since you mentioned ground balancing helped a little.

Try out the other SMF modes and/or try increasing the recovery speed a little bit...and ya, make sure the cable is secure

 

[TheFrood]

I think it's coil-waggle... I thought briefly about this before but never put significant consideration into it.
I'll wrap one of those velcro ties that came with the detector around the lower shaft closer to the coil to
hold it still closer to the shaft and see if that helps. Thank you for the great advice and suggestions!

 

[Diga]

You're welcome. Let us know how it works out.

 

[Ken Clad]

I'll wrap one of those velcro ties that came with the detector around the lower shaft closer to the coil

Since I'm new to a Legend and metal detecting in general, is there any reason you wouldn't want to keep that cable secure at all times? I kept the number of turns around the shaft as few as possible and as wide spaced as possible. I won't bore you with the "why" of any of that, unless you'd like an explanation.

 

[TheFrood]

Since I'm new to a Legend and metal detecting in general, is there any reason you wouldn't want to keep that cable secure at all times? I kept the number of turns around the shaft as few as possible and as wide spaced as possible. I won't bore you with the "why" of any of that, unless you'd like an explanation.

No, you definitely want to keep it secure. I just wasn't keeping it secure enough. I left it somewhat loosely wrapped so that I would have flex and play for extending or retracting the shaft. I will secure it more firmly to the shaft with just enough play to adjust the coil angle but not enough for it to jiggle when in water. Before I just relied on wrapping it around the shaft to loosely secure it which only works if you aren't jiggling the detector or aren't using it in water. I understand the why of it. Just didn't realize quite how important it was.

 

[Diga]

I just put my Legend in All Metal and reduced the first tone break to minimum. I loosened up the coil cable, kept the coil stationary, and wiggled the cable back and forth over the coil. The Legend gave no sound or ID. I doubled checked to make sure everything was ok by trying a small ferrous nail, and a small gold ring. Both of those were detected.

I guess the coil wire has some sort of dielectric shielding.

 

[TheFrood]

I just put my Legend in All Metal and reduced the first tone break to minimum. I loosened up the coil cable, kept the coil stationary, and wiggled the cable back and forth over the coil. The Legend gave no sound or ID. I doubled checked to make sure everything was ok by trying a small ferrous nail, and a small gold ring. Both of those were detected.

I guess the coil wire has some sort of dielectric shielding.

I did the same. I don't have nearly the same issue with salt water in shallow surf which is bizarre. Why would this mainly impact
me while in fresh water and park mode? Ohh. I need to go back to the lake. I think maybe I was in field mode, not park mode...
So perhaps it was over-reacting to certain ferrous signals....

 

[BobOso]

I was selling a 3d printed cable clamp thing on ebay, but now just have the STL file available on a site called Cults. I made them out of a flexable material caled TPU, they are made for the legend and will keep your cable from moving, they are also available for the nox series. It will probably solve your problem

 

[Big Boys Hobbies]

I was selling a 3d printed cable clamp thing on ebay, but now just have the STL file available on a site called Cults. I made them out of a flexable material caled TPU, they are made for the legend and will keep your cable from moving, they are also available for the nox series. It will probably solve your problem

Those are fancy! Very nice!
Velcro works well for me.

 

[BobOso]

thanks Bart, I've used velcro, but could not keep the cable tight enough to suit me.

 

[Beachhunt1]

Those are fancy! Very nice!
Velcro works well for me.

I use high quality electric tape. Even salt water and pounding surf does not affect it much. If it does, just super glue the ends down.

 

[hoser]

I use plastic cable ties and they work great. I never collapse my shafts so the ties can just stay put. My first detector was a higher end Garrett Master hunter and it would false all the time. I read somewhere that the cable needed to be tight to the shaft. I taped it down and problem solved.