Going Over Areas Multiple Times On The Beach

[Jeff McClendon]

On 3/21/2023 at 9:21 AM, Sirius said:

I'm not entirely sure if this is true or not, as I'm not familiar with the inner workings of a metal detector. But i've heard somewhere (probably from a YT video) that moving your coil over a target will send a electromagnetic wave down that charges the target, and this allows it to be detected by your machine.
That being said, I've found it to be very helpful to go over the same areas i've already swung my coil over once because I would find targets I missed during the first swing. My reasoning for this is that the first swing charged the target, but my machine didn't register it initially so I just kept walking. A second swing over the same area should produce a reading as the target is already charged as I walked over it again, thus I can target the object until I get a clearer reading. 
What do you think about this? I would only do this if I found a coin line as I know there would be targets in the vicinity, but it tends to work out. I found a ton of targets I missed on the first swing and even on the second swing; gotta be through just incase there's a ring I missed!

There are many ways a target can be "missed" when going over the same area. Here are a few.

Lack of complete swing overlap/coil coverage is an obvious way.

Using DD coils some targets have different responses at 90 degrees especially if there is a lot of iron trash or iron mineralization. If my detector is setup with full iron discrimination using a DD coil, I may miss some iron masked targets. If I am using some non ferrous notching to avoid aluminum trash a similar thing can happen. Changing the direction of coil approach may change things completely.

Swing speed changes and keeping (or not) the coil at approximately the same height above the surface can effect detection of some targets.

Removing some targets from an area and then hunting that area again even right afterwards can result in targets being detected that seemingly weren't there before since they may have been partially or fully masked by the targets you already recovered in the first pass.

Add to all of that, beaches with tides and wave action are a very dynamic target environment. Just walking/standing on a constantly changing beach can change target depth and position.

[GB_Amateur]

Pulse induction detectors actually take advantage of the decay of the eddy current set up in the target.  The White's TDI detectors allow you to adjust the delay between transmit and receive.  The adjustment range they allow is 10 microseconds to 25 microseconds.  (A microsecond is one millionth of a second.)  This should give you an idea of how long the metal detector's effect on the target lasts.

[ColonelDan]

What you experienced is what I say in my signature...learned only from many years of beach hunting:

The Challenge:  "Big Beach, Little Coil, Tiny Targets."

Simple as that....😉