New User GPX 4500 Noise Issues

[Machineman]

I recently bought a GPX 4500. It came with 3 coils, 14" oval nugget finder advantage, 10x5 coiltek and stock 11" DD round.  I want to be able to run the 14" mono but cant get the detector to quiet down. Lots of EMI noise. At least I think that's what it is. Even when I am out in the boonies. No cell signal and now power lines anywhere it is still noise. The 10x5 coil works better but still has occasional warbles even when holding still.  The DD seems to be quietest. Normal Settings: Factory for the most part. Enhance, fixed, general, mono. Is there a process that I should follow to quiet the detector? I am a bit worried that the 14" coil might be bad because it is so noisy. I am doing auto tune and ground balance. I have already found some nice gold with the detector using the 5x10 coil but feel that I am missing some of the signals because I cant quiet the detector. Thanks 

[phrunt]

The 11" DD will always be the quietest being a DD coil it will handle EMI much better, and the 10x5" will be quieter and less affected by any EMI than the 14".  With the 14" being the larger coil, it's also a larger antenna to pick up any EMI.   

The GPX 4500 is quite a difficult detector for EMI, very sensitive to it, but out in the middle of nowhere should normally be OK although I can rarely find a place that's completely free of EMI with my 4500, even planes can cause it.  Getting the occasional EMI spike or messed up threshold is pretty normal. 

Even though you've got no cell phone signal your phone will be trying it's butt off to get a signal, that can make it produce worse EMI than if it's got a signal,  A reasonable solution to phone EMI is to go into Aeroplane mode, as a test I'd switch the phone off though and see if anything improves, it will certainly help with occasional EMI spikes.  Noise when holding still is normal for EMI, noise only when moving the coil is less likely to be EMI.

Is the coil still erratic if you turn the gain right down low of something like 4? Also, if you switch it into Cancel is it still noisy?  Doing those two things may help diagnose a bad coil as I would expect it would still play up with a lower gain, or possibly in cancel if it was faulty. 

It's hard to help much more without seeing a video of what it's doing and sounding like but it does sound a fair bit like it might be a bad coil, just make sure it's cable is done up tight.

[LuckyLundy]

Turn your Threshold down and your Gain, doesn’t need to be Maxed out either.

Rick

[Machineman]

phone was off last time I was having issues. I normally run the gain between 8 and 10. Would a bad coil still make noise standing still. Also what would I lose in depth and sensitivity running the DD vs the 14" mono. I know the 10x5 mono will be more sensitive to smaller gold. I found a .25 gram nugget with it the other day. I have only really been using the 10x5. So far I have a about 14 grams found with it. I would like to get more depth in the area I am working. Thanks for the advise

[phrunt]

Yes, depends what's wrong with the coil, loose windings will make noise mostly only when moving, especially when bumped. 

EMI typically is the one making noise when holding still especially if you hold the coil up in the air and the noise from EMI generally continues when you move the coil around too.

If the coil has been drowned in water it will typically make EMI type noise all the time, still or not.

There are no doubt other faults I haven't mentioned that will cause noise too, it's not really possible to give a definitive answer as many things cause the same symptoms.  It could even be the ground in the cable is damaged.

Coils can get noisy as they age with the foam inside breaking down or adhesives failing and so on, a whole host of reasons and that NF Advantage is a pretty old coil.

Sensitivity and depth are very debatable between the 11" DD and 14x9" NF Advantage.  The NF will likely give more depth in most situations on bigger targets and sensitivity it's a tough call but you've got the 10x5 for that anyway.  You can flick the switch to mono while running the DD and run half the coil and get a bit of a boost for small gold sensitivity on the DD if you're cleaning up a little area.

To me it sounds like you feel the Nugget Finder is faulty, and it does sound the case if it's operational noise is vastly different to the Coiltek 10x5 on the same settings.

Perhaps someone else might have some more advice for you.

[Machineman]

Thanks for the information. I am going to take all three coils out tomorrow and test them in as quiet a place as I can find.