Manual Vs. Auto Noise Cancel. Please Don't Hit Me

[MHirschmann]

I know I am beating a dead horse here as NC has been beaten to death in the past on this forum but lately I have been wondering about this topic again. How many of you are manually choosing your NC channels? I have not ever manually chosen my NC channel but I do auto NC several times during every hunt. I know there are quite a few of you out there that manually choose your NC channels and I was wondering what you do to determine which channel to use. Is auto NC truly as good/accurate as choosing the optimal channel manually? Sorry for bringing this up again but I can't seem to get a clear answer as to the correct way to optimize the NC feature. I almost always hunt in manual Sens and go with whatever NC channel my machine decides to use. Thanks for your help and HH -Marc

 

[hershey1]

There have been times when I have used manual to find a quiter channel also if you are hunting close to another machine manual will find a channel with less or no interference. If your threshold is somewhat erratic manual will help with this also. Just another bell you can shake or whistle you can blow if you need too. HH

 

[Southwind]

I try and use the lowest channel I can without my detector getting noisy. I seem to find more stuff on channel 1 than channel 10

 

[moonshine]

I dont even remember the last time i messed with the channel or noise cancelled. i think its on channel 6. been like that for months. every time i noise cancel it comes out to 6 or 11 usually so i figure why waste the time messing with it when i should be swinging. i have tried setting it to 2 or 4 but then i get a lot of interference. either that or i run my sens. too high. (i keep it at manual 24). I dont know.

 

[stasys]

I agree with Southwind, Different channels works a bit differently, usual auto noise cancel gives me 11 chanel but i like to use 1 or lower than 11.

 

[EtracTom-AdirondacksNY]

I auto NC and get either 6, ,9 10, or 11 around here. Never thought to try to pick a manual channel but read on here a while ago that someone said that lower channels like 2 or so got better results for coins for him so I may experiment with that next year some too as well as going over areas in manual I've been in in Auto sensitivity already to see what turns up.

 

[Yeasty]

This is my opinion:
Fact: Lower NC# = Higher transmitted frequency = better response from coins and other high conductors..
Fact: Higher NC# = Lower transmitted frequency = better response from gold and other low conductors.
When detecting over dirt I use a low NC#.
When detecting on the beach I use a high NC#.
The above settings are irrelevant if there is a lot of local EMI. In that case it's better to just let the machine find a quiet channel.
Again, it's just my opinion.

 

[Idprospector]

Very interesting Yeasty, I auto cancel all the time and have found as many gold items as I have silver. My etrac picks a high channel every time. Idigid

 

[Cladiator (OR)]

I did some testing awhile back in my test garden-using a 10X12 SEF coil while manually working my way through all 11 noise channel settings and manually adjusting the sensitivity settings until I received what I perceived as a valid response to the target buried below. My un-scientific results indicated a very slight advantage (1-2 lower sensitivity levels) for the lower (usually 6 and below) noise channels (i.e.- I could pick up a quarter at sensitivity 15 for noise channels 1-6, but for noise channels 7-11 it required a sensitivity setting of 16 or 17 to detect the quarter). Of course, I can't tell you what kind of electrical noise in the area of my test garden was effecting my results-I would expect this to probably change from site to site. I personally auto-noise cancel at each site I visit (sometimes more than once depending on where I am and the perceived electrical interference sources I am near (power lines; cell towers; etc.)).

 

[Jason in Enid]

Yeasty, you got you're facts backwards. Lower frequencies work better for coins and silver, higher freqs work better for gold. That is why coin machines use something around 6Khz and gold machines use around a 15Khz.

 

[earthmansurfer]

Yeah, Jason has that right on. But, the E-Trac appears to be using two frequencies combined, one higher and one lower, so it's not that channel one is a higher frequency than channel 11. It might average that way, but they are using "frequency sets" by all I can gather via posts. It might look something like "channel 1 - 4kHz & 15kHz", "channel 11 - 2kHz & 12kHz" - just a guess.

Stasys - So, if the lower channels are higher in frequency and the higher channels are lower in frequency, then this is why you mentioned before that channel 11 (I think you said that) was better to "see through" iron? That makes sense. What channels have you found are better for what and how did you test this?

I noise cancel every 30 minutes or more if I change spots at the field I'm hunting. I often get a different channel and there is very little EMI there! I change often just to try to see if I can spot any trends, nothing thus far...

Albert

 

[Yeasty]

Thanks, I stand corrected. It should be:
Higher NC# = Higher transmitted frequency = better response from gold and other low conductors.
Lower NC# = Lower transmitted frequency = better response from coins and other high conductors.
I just reverified this with my O-scope.

 

[Yeasty]

Here is a picture of the ETrac transmitted signal. The smaller square waves determine the CO measurement. They generate harmonics between 1.5KHz and 100KHz in the target for the receiver to analyize. The transmitted small square waves are at 45KHz +/- 5KHz, varied by the NC number.

This is a good article from MineLab that covers it:
http://www.minelab.com/__files/f/11043/METAL%20DETECTOR%20BASICS%20AND%20THEORY.pdf