Coil Bump False Signals-What Causes Them And Solutions?

[GotAU?]

I just like the title says, what causes false signals from coil bumps? I assume it’s from the Litz wires moving a little bit inside the coil, so can it be alleviated by filling a coil with a dense foam, or epoxy if you don’t mind the added weight? An older coil on my GB2 seems to have this issue and I am tempted to try filling it with foam as an experiment.

[phrunt]

Minelab have had the problem with the Equinox and GM1000 onwards in the detectors I've owned from new, I don't think it's as simple as epoxy in their coils, they appear to make very well built coils, and it tends to only happen in gold modes more so than other modes so it's something to do with the higher frequencies being more sensitive I guess, I really have no idea but other detectors like the Deus 1 and Gold Bug 2 that run higher frequencies don't have the problem for me nor does the Garrrett 24k..  

It's seen in older GPX coils like the Commanders too but that's more age related and I'm sure that's movement in the windings, if you see how those things were made with masking tape and just overly poorly made coils.  Some of the older Coiltek's are famous for aging bump sensitivity too.   I think if you have a noisy coil that never used to be noisy then filling it with epoxy would likely resolve it.

[mn90403]

11 hours ago, GotAU? said:

I assume it’s from the Litz wires moving a little bit

Have you noticed the sound if your detector is on the ground and something is dropped on the coil?

[GotAU?]

No, I can try it.  What does it mean when that happens? 

[GotAU?]

3 hours ago, phrunt said:

Minelab have had the problem with the Equinox and GM1000 onwards in the detectors I've owned from new, I don't think it's as simple as epoxy in their coils, they appear to make very well built coils, and it tends to only happen in gold modes more so than other modes so it's something to do with the higher frequencies being more sensitive I guess, I really have no idea but other detectors like the Deus 1 and Gold Bug 2 that run higher frequencies don't have the problem for me nor does the Garrrett 24k..  

It's seen in older GPX coils like the Commanders too but that's more age related and I'm sure that's movement in the windings, if you see how those things were made with masking tape and just overly poorly made coils.  Some of the older Coiltek's are famous for aging bump sensitivity too.   I think if you have a noisy coil that never used to be noisy then filling it with epoxy would likely resolve it.

I’ll have to do an experiment- it’s the larger of my two coils for the GB2 and it came stock with the detector- from Fisher in Los Banos,  so it’s old.

[phrunt]

The Gold Bug 2 coils are very complex inside  The Concentric windings wouldn't need to move much to cause problems.

[TheDeepseeker]

2 hours ago, phrunt said:

The Gold Bug 2 coils are very complex inside  The Concentric windings wouldn't need to move much to cause problems.

Crikey, there's a lot more going on inside there than I realized!

[GotAU?]

Simon, is that a top view or bottom view? Thanks for posting that, it’ll help to know where to drill the holes while avoiding the wires and coils to inject the foam!

I wonder what those spiny looking wires are at the top and bottom? They don’t look connected at all, maybe a ground plane that works through induction?

[phrunt]

10 minutes ago, GotAU? said:

Simon, is that a top view or bottom view? Thanks for posting that, it’ll help to know where to drill the holes while avoiding the wires and coils to inject the foam!

I wonder what those spiny looking wires are at the top and bottom? They don’t look connected at all, maybe a ground plane that works through induction?

this is from @strick and it's the 6x3" coil not the 10x5".  It's a top view.  There will be some paper in there with shielding paint those wires are attached to more than likely.  I'm not sure drilling holes and trying to inject foam is a good idea, I wonder how hard it would be to cut the top off the coil, and do it that way, injecting foam is likely to move stuff around that shouldn't be moved.