Noise Cancel... It Always Changes..?

[fastdraw]

Ok.... With only 14 months detecting experience, I always forget to ask this question.... but it just popped into my head , So I thought I better jump on it before I forget again. So here is my scenario and follow me. I'm 60, so just humor me with this question.

1. I get to my first metal detecting spot, and I am several miles away from any known or seen electrical interference, and I even look for jetliners in the sky before I use the noise cancel function. I usually leave my cell phone on, but I usually leave it in the truck.

2. The first thing I always do is a noise cancellation on my Nox 600. Which displays -5. (For Example) Then I ground balance, carefully..!! and then I check my results with a test coin

3. The results are NOT good with my test coin..!

4. So I repeat the process starting with noise cancellation first. And the noise cancellation comes up + 7

5. What just happened..???

6. Noise cancellation just went from -5 to +7 In less than two minutes..!

6. The careful ground balance that I do on the first and second try are usually within one number.

So just how important is the noise cancellation....? Sometimes I'll repeat the noise cancellation three or four times and the numbers are never the same..!

 

[jmaclen]

How do you do a noise cancel? Are you holding the coil away from the ground and pointing at a known source of EMI like distant power lines, cell towers, airport or town? Are you holding it with the coil pointing in the same direction when you get different numbers?

In the manual Minelab says that an auto noise cancel will pick the quietest channel out of 19 choices and takes 8 seconds. EMI can change even with a slight change in wind direction or intensity. I used to run a Minelab GPX 5000 a lot. Noise cancel took almost 1 minute to run through over 200 different channels and they were rarely the same if I stood totally still with the coil pointing at the horizon and repeated the process. My SDC 2300 takes almost 45 seconds to decide on the quietest channel.

Ground balance is fairly fixed if you are on the same type of dirt with the same amount of moisture. EMI, even in the middle of nowhere can change instantly.......if your phone can get a signal and connect to the internet at your site there is EMI for sure.....if you don't have phone service but can still get AM radio, you have EMI. Lightning or any source of static electricity can cause localized EMI.

 

[IowaRelic]

Noise cancel makes more sense how it works to me than the ground balance. I have a hard time getting a good reliable GB so I usually leave it at 0. It does seem to affect its target response big time. Sometimes the machine is more calm when I balance it. Other times it seems to react more to the dirt. 0 seems to work all around. Here’s a question, does multi need balanced or is it for single freq?

 

[jmaclen]

I forgot to mention that the relationship between EMI and sensitivity levels definitely matters. Audible EMI even after doing a noise cancel means turning down the sensitivity and maybe doing another noise cancel until actual targets are easy to hear.

Iowa Relic, I read this paragraph religiously which is from the Equinox manual page 15, since I hunt in moderate to high mineralization and am often after small deep targets:

Ground Balance
Ground Balance is a variable setting that improves detection depth by reducing noise in mineralised ground. Mineralised ground may contain salts, e.g. wet beach sand, or fine iron particles, e.g. red soil. These minerals respond to a detector’s transmit field in a similar way that a target does. Due to the much larger mass of the ground compared to a buried target, the effect of mineralisation can easily mask small targets.

 

[CT Todd]

I aware that the answer to this question is always noise cancel. But I don't. If I have a smooth operating machine with no sign of chatter or anything else problematic, I don't fix what ain't broke. The point is to shift your operating frequency away from an interference. No interference no problem to solve. Get out there

 

[kschae4]

Coming from the Safari, guess that I'm a little superstitious. so I routinely NC and GB during each hunt maybe once an hour. Helps me think I'm getting optimal performance.

 

[fastdraw]

Coming from the Safari, guess that I'm a little superstitious. so I routinely NC and GB during each hunt maybe once an hour. Helps me think I'm getting optimal performance.

I do the same

 

[fastdraw]

How do you do a noise cancel? Are you holding the coil away from the ground and pointing at a known source of EMI like distant power lines, cell towers, airport or town? Are you holding it with the coil pointing in the same direction when you get different numbers?

In the manual Minelab says that an auto noise cancel will pick the quietest channel out of 19 choices and takes 8 seconds. EMI can change even with a slight change in wind direction or intensity. I used to run a Minelab GPX 5000 a lot. Noise cancel took almost 1 minute to run through over 200 different channels and they were rarely the same if I stood totally still with the coil pointing at the horizon and repeated the process. My SDC 2300 takes almost 45 seconds to decide on the quietest channel.

Ground balance is fairly fixed if you are on the same type of dirt with the same amount of moisture. EMI, even in the middle of nowhere can change instantly.......if your phone can get a signal and connect to the internet at your site there is EMI for sure.....if you don't have phone service but can still get AM radio, you have EMI. Lightning or any source of static electricity can cause localized EMI.

jmaclen gave a good answer... and I got several other answers. But nobody really answered the question and maybe there is no answer. If you do a noise cancel, and go from a - 5 to a + 7 just by pressing the button. What Happened
Hold your detector out in the same position and do a noise cancel one right after the other, and the numbers will not be the same.

 

[Elmy]

Your detector should have an auto tracking ground cancel.....may try that and forget all that manual canceling.