ground balance of coil issue

[jas415]

Yesterday I put the stock middle sized coil on and started to hunt, I noise cancelled, then started swinging. Each time the coil got within an inch or so of the ground I would get a deep short hjm sound. I then took it and did one of the forund balance motions, moving the coil up and down to within an inch of the ground and each time it would give me a deep short hum sound. I noise cancelled again, 18" above the ground, same issue, then I put the coil on the ground and noise cancelled. Same issue. I ran the manual sensitivity down to about 15, the auto was showing about green 17-18. Same issue. Then I switched to Auto + 3, then back to auto 0, and still the same issue. So I said to hell with it and hunted as it still gave me targets and correct tones. I also had a backup program, the stock 'coin' pattern selected, and it did it in that mode also. After maybe 10 minutes I no longer had the hum when near the ground. To ensure there wasn't an iron object causing the 'hum' I moved at least 10 times, but it only happened when the coil was within an inch or so of the ground. It was hot, about 85, dry no rain in at least two weeks, and no power lines or pipes nearby. I have no clue!

I rarely hunt with the bigger coil and prefer using the small one all the time. I just went out and tried it in my front yard, stock middle size coin, same settings, etc., and all seems well. Maybe it just had a brain wave!!

 

[trojdor]

Perhaps a silly question, but is your manual Ground Balance option unchecked/off (as it should be)?

 

[jas415]

Unchecked. Machine was working perfectly with the small coil. I shut it off, changed coils, and instantly it had the deep hum issue when the coil got close to the ground surface. Not long drawn out but short like an iron grunt but a deep hummm. I dont think it is anything for me to be really concerned about, just wanted to see if others had experienced the same thing. After 5 years with the 3030 and hunting 170-200 days a year with it, I tend to notice when it hickups or gets gas.

 

[trojdor]

I tend to notice things like that as well...and that's a new one for me.

I wonder if you had some underground power cables near the search area?

Otherwise, I'm at a loss...

 

[dewcon4414]

Odd....... but sounds like it took the machine some time to GB to the soil/EMI. Kind of like some machines with auto GB and swinging over a target several times...... eventually it GBs out weak signals or starts loosing depth. Even headphones could do it...... since they do determine what is heard based on speaker response as they get older you hear some strange stuff. Hunting in salt water you get a lot of issues with headphones.

Dew