Strange Feedback

[berryman]

I have two, possibly three, different detectors that sound off when the coil taps or hits the ground (and there is no target under the coil). One is a Fisher, one is a Whites and one is a Tesoro. I've checked for loose connections, but have found none. If it were just one detector I'd think that I might be dealing with a bad coil. But having the problem with three different detectors (two of them fairly new), suggests that it's probably not a coil problem. Any thoughts on what might be causing the problem?

BTW - I do all my hunting on dry sand beaches.

 

[Hightone]

Do they all three use a ground balance adjustment? I attributed my sometimes false signals on the CoinGT to the Ground Trac as I swung. It's making adjustments every few seconds to counter the ground. Maybe a jolt during that process causes a beep. I don't know for sure, but that's the best I came up with. My F5 would also. Not the preset F2 though.

 

[berryman]

Two of them have automatic ground balancing and one requires manual ground balancing (the Tesoro).

 

[foreign object]

GB to high would be my guess.

 

[bootyhoundpa]

Might be running the machine just a little too hot... you could lower the sensetivity or signal balance but to tell you the truth i kind of prefer running it hot...as long as you know when its falsing then its no big deal...

 

[MarkCZ]

As far as I know every detector I ever had did the same thing, the older box coils were worse to do it, but just this evening I was out with my Coinstrike and I bumped the coil a couple of times and the detector chirped.

Mark

 

[WV62]

My 2 cents worth, mine does the same thing, but I have always thought it was picking up a little movement of the coil wire near the coil. Mine will also do that if I stick the coil in some brush and short swing it and the coil or the cable come in contact with the brush.

Now that's my story and I am sticking to it.

Ron in WV

 

[Tom Slick]

Most all detectors will do this with most all coils. Your best bet is to stop BANGING your coils on the ground. One of my detecting buddies came off a grass field at the park the other day and he had fresh grass clippings stuck to the top of his coil on his MXT. He was standing in the parking lot on the asphalt and he turned his detector and started banging the edge of the coil on the asphalt to get the grass to fall off. I witnessed this the day after I loaned him a BigFoot coil so he could see how he liked it. After explaining how coils are manufactured and how deliberately banging them on the ground isn't the best thing for them, I told him that If I saw him do that to one of my BigFoot coils, I'd do the same thing to his head and see how he liked it. I'm amazed at how some folks treat their equipment. And yes, I know berryman, and he respects his equipment and takes care of it like I do mine.

 

[BillF]

My X705 does it also.

 

[GeorgeinSC]

My Sovereign GT and Excalibur II both will do the same thing. I do not think that it is an unusual occurrence.

 

[Oldguy]

Wrap the wire from the coil to the lower rod in the direction that gives the most distance between the wire and the receive element of the coil. On Tesoro the coil wire is behind and to the right of the receive coil element (the small coil in the center). So on Tesoro the most distance is gained by wrapping the wire in a clockwise direction when viewed from the top. Leave just enough wire to allow movement of the coil and secure the wire to the lower shaft as high as you can on the lower shaft using a Velcro cable tie. That will reduce or eliminate falsing due to wire movement.

 

[MarkCZ]

And when I say mine does that when it gets bumped, I don't mean that I bang it around, sometimes all its takes is a little tall mound of stiff rooted or stocky grass, or maybe a ridge of a tire rut that you just bump why your swinging the coil. I don't like it when it does that because I know that the response is due to impact so I avoid it as much as possible.

Mark

 

[Monte]

There are a few things which can lead to 'noise' when a search coil is tapped or bumped or shaken around.

Does it happen often? Yes.

Can it happen with any brand of detector? Yes, most of them will, at times.

Are there some basic things to check for that might be causing this noise that the operator can address? Yes. Check the following short list of five [size=small](5)[/size] things than can cause this 'noise.'

#5 Cause: A search coil that is not firmly secured to the lower rod and allowed to 'flop' around can cause 'noise' as it moves the inner search coil windings towards-and-away from a metal lower rod or coil cable.

#5 Solution: Snug up the search coil so it doesn't flop around.

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#4Cause: A loose search coil cable that can flop around or move up-and-down the rod system, all of which can cause some false signals as it is metal moving in the search coil's EMF.

#4 Solution: Properly wrap the coil cable so it doesn't move and isn't loose. I usually wrap the coil cable over the top of the lower rod, about 6" up from the stand-off or isolator, secure it in that position [size=small](with just a little looseness to allow for a little search coil flexing)[/size] using either snugged-up Velcro® or black electrical tape. I then wrap the remaining coil cable up the lower and middle rods to a point where I again secure it, snuggly, allowing a comfortable curve in the cable to go to the connector jack.

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#3 Cause: Operating with the Sensitivity, Gain, Signal Balance, Pre-Amp Gain, Rx Gain, or other sensitivity related setting too high or too close to the "ragged edge" of operation that can lead to signal instability.

#3 Solution: Back off a bit on the higher Sensitivity [size=small](all of the above references)[/size] setting a little.

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#2 Cause: A poorly designed search coil or one that might be defective and require service.

#2Solution: Replace or repair the search coil.

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And the #1 Cause for this type of periodic 'noise' from a search coil, of any size, shape, or internal design.: The search coil is, or should be, a more delicate part of the detector design which requires the proper sizing, shape and positioning of the internal wire windings in the coil housing. In most cases you will have at least two inner wire windings, one for Transmit and one for Receive, and there will be additional things like a 'pick-up' wire positioned to help balance the coil for peak performance, as well as some small electronic components.

All of these items, which have metal and also have to be properly positioned for best signal balance, then need to be secured as firmly as possible in their functional position. To have a highly sensitive detector to respond to the smallest and deepest or weakest target disturbance of the EMF, you need such a very sensitive search coil. Other than 'sensitive,' let me use the term 'delicate' because all of the internals of a search coil must be motionless from each other so as to allow the detector to function at its best.

Sometimes any of the above four things might help eliminate some of the causes for 'noise,' but due to the 'delicate' wire windings and component positioning inside the search coil, especially if operating at a much more sensitive control setting, any abrupt bumping or jarring, or vigorous wiggling or shaking of the search coil, can cause micro movement of any of the internal wires and metal components such that you will be able to hear a brief response from that internal disturbance from shaking, jarring, tapping or bumping the search coil.

The #1 Solution: Don't shake, jar, tap or bump the search coil. Pretty simple, and all of these things can apply to any make or model. They are delicate transmit & receive devices and should be pampered.

Monte