Questions for the Exports - Sensitivity Switching

[CCadrin]

The question I ask is besides 'Noise Cancel' and selecting the appropriate program, is there anything else you guys do every time you turn on the detector? One post I read is the noise cancel with the coil on the ground. Also I read to Noise Cancel often (every 30 minutes or so). I tried and saw no difference so it did not harm my performance.

The reason I asked this is that I have experienced two different scenarios and I'll describe both. I went to a salt water beach and I was detecting mostly dry sand and maybe a little slope. The detector was in the standard beach mode and was acting a little erratic. Nosie cancel did not do much. I then switched to auto mode for a few minutes. I reverted back to the same manual mode and the machine ran very smooth. So by going into 'auto' seemed to smooth out the erratic behavior.

The second scenario I was testing in my test garden. It was a custom program and I as testing 'recovery deep', 'recovery fast', 'sea water' and different target separations. All were checked and the mode was 'ferrous coin'. In manual sensitivity, the coins would hit and jumpy. I then switched to auto mode and tried to hit the coins in the garden. Not much difference. I then went back to manual mode and retested. The hits were less jumpy and more stable.

So the conclusion is to run in auto mode for a few minutes before switching to manual mode and then noise cancel. Occasional, I use to use this approach on my Sovereign GT. Can anyone confirm that they have experienced my findings or add to the turn on and go procedure?

 

[Jason in Enid]

I think your smooth operation after switching from manual to auto to manual was coincidence. Unless you changed the manual sens level, it would have gone back to the same it was before. So if no other changes were made, you had some mineral or EMI interference originally. I haven't seen that behavior in my CTX, but I will play with manual/auto settings and see if I can duplicate it.

When I turn on, I first scan the ground to find a clear patch that I place the coil over to perform the noise cancel. That is the only thing I do when I turn on my detector other than just searching.

 

[huntindog1]

Are you talking about Auto Sensitivity? and Manual Sensitivity? As switching to manual sensitivity and how the detector reacts depends on the level of manual sensitivity is set at.

As far as noise canceling I hold my coil up off the ground about 12 inches when the detector is noise canceling. Its basically just trying to find which channel is the quietest and then picks that channel to operate at.

Now if you are talking about auto ground balance which is different than noise canceling or the sensitivity setting , then when the ground balance box is un checked then the machine is in auto ground balance. If you put a check mark in the box then you have to go thru a manual ground balance procedure which can be found in the operating manual that came with the detector.

 

[Bryan V]

So the conclusion is to run in auto mode for a few minutes before switching to manual mode and then noise cancel. Occasional, I use to use this approach on my Sovereign GT. Can anyone confirm that they have experienced my findings or add to the turn on and go procedure?

Yes. I have been doing the same thing.
I've had my CTX less than a year and just recently started using manual sensitivity trying to push the power.
A lot of times when I first tun on the detector and the manual sensitivity is set high the detector runs real erratic.

I put it in Auto + 3 for a few minutes and start detecting.
After that I put it back in manual sensitivity at a higher sens. and it seems to run much better.
It will sometimes happen in the middle of a hunt too.
If I do a noise cancel and it doesn't get get better I will drop the power or go back in to Auto
for a few minutes, then work my way back up and all is good again.

I'm not sure what is going on but it definitely works for me.
Bryan

 

[CCadrin]

Thanks Bryan. I am not crazy.

 

[glenn3-88]

I've never run auto + but maby a couple of times. I have already ran sensitivity about 3 points
above what the screen tells me. If it drops 10 I manually ground balance. Very few times have
I ever had occasion to have to do that. When at the beach I run it as high as possible without
it getting noisy and that's usually 26 to 28. However, I do run seawater on.

 

[Bryan V]

Are you talking about Auto Sensitivity? and Manual Sensitivity? As switching to manual sensitivity and how the detector reacts depends on the level of manual sensitivity is set at.

As far as noise canceling I hold my coil up off the ground about 12 inches when the detector is noise canceling. Its basically just trying to find which channel is the quietest and then picks that channel to operate at.

Now if you are talking about auto ground balance which is different than noise canceling or the sensitivity setting , then when the ground balance box is un checked then the machine is in auto ground balance. If you put a check mark in the box then you have to go thru a manual ground balance procedure which can be found in the operating manual that came with the detector.

In Andy Sabisch's CTX book he says that the Minelab manual instructions for performing Noise Cancel was incorrect..
The correct method is to rest the coil on the ground with no metal underneath..
"This ensures that the channel selected is the one that factors in the ground feedback as well as any outside interference seen by the coil on the ground which is what the detector will see when you are hunting."

 

[trojdor]

In Andy Sabisch's CTX book he says that the Minelab manual instructions for performing Noise Cancel was incorrect..
The correct method is to rest the coil on the ground with no metal underneath..
"This ensures that the channel selected is the one that factors in the ground feedback as well as any outside interference seen by the coil on the ground which is what the detector will see when you are hunting."

I agree with Andy on this one. Based on my tests, the more mineralized the ground...the more improvement this makes.

Also...here's a tip that borders on hoodoo;
Instead of finding a clean area to lay the coil (to NC), when hunting in dense iron...lay the coil on top of some (moderately deep) buried, un-dug iron...then Noise Cancel.
The idea is to try to eliminate the extra noise that iron enhances.


mike

 

[Johnnyanglo]

The idea is to try to eliminate the extra noise that iron enhances.


It's a well guarded secret how the FBS machines fully operate, but there are some things known or assumed based on limited evidence. IMO, the noise cancel circuit is not associated with how iron is measured and identified by the detector algorithms. Noise cancel should have no effect on eliminating iron signal in the ground. It does shift the operating freq and its main harmonic a tiny bit to avoid interference from other sources of radio noise. Adjusting any detectors operating frequency a tiny bit should have no relation to how the soil minerals are analyzed by the detector's algorithms (comparing short and long pulses with low and high freqs to determine the nature of the target).

Now ground balancing a VLF detector would be affected by metal in the ground or minerals - but the FBS hybrid detectors don't require ground balancing under normal operating conditions.

Since no one but the ML engineers have a clear understanding of the FBS machines, and they're not talking, it is possible that switching to Auto+3 and then back to manual sensitivity better reflects the soil conditions as the Auto mode is making accurate measurements to offset the mineral response algorithms which may be held forward when back in Manual mode to keep the detector more stable for a time. Running in Auto+3 might give the detector the stability because the variables are more accurately fixed in Auto, and continue to be held in Manual, at least to some degree for a period of time. I will have to check it out as I've not noticed this effect - but it seems possible. Wish they had Auto+6 and such, would be a big plus all around.

john

 

[amberjack]

never have seen mine run as smooth in manual as auto plus 3 like get say 22 plus 3 running smooth and then go to 25 manual and its always been more chatty, maybe sneaking up on 25 might be worth a try.

I always thought minelab FBS machine worked best as smooth as possible, not scared of the chatter I run a F19 chatty machine and works well chatty and I am used to it.

I think of the ctx as my limo I want to enjoy the ride in comfort and leave the others to stock car racing but that's just me

as the saying goes what ever works hey


AJ

 

[Jason in Enid]

Oooooh, I'm going to have to try the NC over iron on my next hunt to see if it helps any.

The NC is interesting, because it is NOT just listening for interference. If you have ever done a NC next to a buddy's detector, you will see that the CTX goes through each channel, transmitting and listening before it picks the quietest one. So doing this over a buried iron target could force it to pick the channel that ignores iron the best.

 

[gabbyhayes]

Oooooh, I'm going to have to try the NC over iron on my next hunt to see if it helps any.

The NC is interesting, because it is NOT just listening for interference. If you have ever done a NC next to a buddy's detector, you will see that the CTX goes through each channel, transmitting and listening before it picks the quietest one. So doing this over a buried iron target could force it to pick the channel that ignores iron the best.

Noise cancel in all detectors FBS and VLF just change the frequency ever so slightly to help minimize interference from outside sources including other detectors.
Changing the position of the coil can and will probably affect the frequencies it chooses.
On my V3i when you pull the pinpoint button you can see any interference, and by rotating 360 deg. you can watch the level of the various interference change rather dramatically.
So I can see where varying the position of the 3030 coil can have a fairly significant effect on which frequencies it chooses.

 

[trojdor]

The idea is to try to eliminate the extra noise that iron enhances.

It's a well guarded secret how the FBS machines fully operate, but there are some things known or assumed based on limited evidence. IMO, the noise cancel circuit is not associated with how iron is measured and identified by the detector algorithms. Noise cancel should have no effect on eliminating iron signal in the ground. It does shift the operating freq and its main harmonic a tiny bit to avoid interference from other sources of radio noise. Adjusting any detectors operating frequency a tiny bit should have no relation to how the soil minerals are analyzed by the detector's algorithms (comparing short and long pulses with low and high freqs to determine the nature of the target).
john

John,
I think you misunderstood...and I think it's entirely my fault for not being more precise.
What I should have said (in more detail) was:

The idea is to try to eliminate the extra EMI noise that iron enhances, by allowing the machine to choose a cleaner/clearer channel during the Auto Noise Cancel process.
This should help depth (and stability), by getting the very cleanest NC channel, and help minimize the effect 'Silent EMI' can have on depth.

I've tested it, and I've seen it work.

In no way was I suggesting the iron would be processed differently, or how it's eliminated. It's still the pain in the ... it always is.

I always enjoy seeing you're well thought out posts.
Please continue, and

HH
mike

 

[trojdor]

Oooooh, I'm going to have to try the NC over iron on my next hunt to see if it helps any..

Jason,
Yes, try that out and see what you think...I think you'll like it.
Every little bit helps. (especially in those 'pounded' areas)
Having everything adjusted as optimally as possible can make the difference between barely hitting...or barely missing a target.

mike

 

[Jason in Enid]

Yeah, I understand what you are saying. When you hit many of those iron targets, the target-trace is all over, just like EMI or bad ground responses. If you can help the machine deal with that just little more, it can help find those good targets mixed with iron junk.

I think I will take some marker flags and mark some spot I think are coins next to iron. Then re-GC over single iron object and try the junky targets again. If the stupid wind here in OK will ever get below 30mph, I'll try to make a video of it.