FBS, Noise Cancel, Spread Spectrum!! (Want Silver?)

[nalc472]

I thought I would post under my own so all can see. I think this is a theory that might help others.

I used to be a Signals Analyst in the Air Force. I gave it some thought and came up what I think is going on with the FBS. I am aware of that type of system of spread spectrum from my AF days.
spread spectum defined:

This is a technique in which a telecommunication signal is transmitted on a bandwidth considerably larger than the frequency content of the original information. Frequency hopping is a basic modulation technique used in spread spectrum signal transmission. here is the link if U want to read about it. https://en.wikipedia.org/wiki/Spread_spectrum

I put it like this. Take a ruler and give it 100 marks on it. Start at 1.5khz and space out 28 signals all the way to 100khz.So say at Noise cancel 1 it is starting transmitting at 1.5kz on the low end. move to setting 2 and the ruler shifts to 4kz at the bottom. Time U get to 11 noise cancel it is to around 35kz on the bottom freq. So it always seems to start at Noise cancel 6 or around 16khz. So if I want to get silver I will start at the Noise cancel 1 to make sure 1.5khz is my starting point and move up only as needed. I do not want to move my "Ruler" of freqs over past say 5hz on setting say 3 (if 5khz)_. I know 1.5 freq has to be in the Noise cancel 1. Just an idea to think about.

 

[Bryan V]

Has anyone done any testing on a buried silver dime with all channels in different locations
to see if these noise cancel channels truly do make a difference in accordance with conductivity of the target?
In a random air test in my house using a silver dime there seems to be no obvious pattern.
The numbers jump all over.
Channel 1 and 11 are the worst and 6 is the best at over 1 1/2 inches more than 1 and 11.
The other channels are in between and roughly the same within a 1/4 to 1/2 inch.
Thanks,
Bryan

 

[nalc472]

Air test are far different than ground test. I noticed last time I was out that noise cancel 1 was very EMI but when I switched to Noise channel 2 it completely disappeared. I think channel 2 might be around 5khz o low side. I want to achieve that freq. I started picking up signals clear in the 12-35 range that I missed first 2 times around. This is in 2 tone ferrous mode.

 

[Bryan V]

That's why I asked if anyone had done any in ground testing at different locations.
I have no clue how this works but I'm thinking the the differences between the channels are very small.
I don't think the detector is running like a 35kHz detector on channel 11.
That would be a drastically different performing detector.
I might be misunderstanding you and I should probably stay out of thes technical discussions
because I'm WAY out of my league.
Interesting subject though. I'm always looking for an edge.
Bryan

 

[nalc472]

I am not sure what the min khz is at noise cancel of 11 but it must be a lot higher than setting 1. Say it is at 22khz at 11 and 1.5 at 1. Not knowing how it is spread out in between. I just picture the 28 freqs spread out from 1.5khz to 100khz at the beginning. It is how far you want to move the "Ruler over" in the freq spread. Try the Noise cancel at 1 using TTF and only move higher to get rid of EMI and let me know what U think. I believe U will be surprised. I had better luck at cancelling EMI that way than the noise cancel button on the screen.

 

[jd88047]

Still testing. On actual hunts messing with noise cancel on manual you can hear a signal degradation. Etrac will still hunt, but I went back to auto which is usually a 6 or 7. I was wondering if I could skip the first two inches of dirt doing this and get a deeper targets. Need more practice yet.

 

[nalc472]

It should be deeper in the lower Noise cancel setting and pick up more deeper response.

 

[Bryan V]

I just did a test on my 10" Silver Rosy that was planted a little over a month ago in my yard.
I have fairly tough ground here in the Pacific Northwest.
I used 20 manual sensitivity with a pattern blocked from 24 to 35 and new Gen 5 Nel Tornado coil.
I could get a 2 way hit swinging North South in all channels with ch. 8 and 10 giving the most accurate VID.
East West is much harder and only ch. 3 hit it solid one way and all other only hitting occasionally..
Channel 9 is what the Etrac picked when doing a noise cancel and it is the channel that hit strongest on the North South swing.
All in all there was very little difference between all the channels except for the fact the upper 8-11
channels posted an occasional better VID.
After this test I don't think I'm going to fret too much about the noise cancel other then to make sure it's running quet as possible.
Bryan

 

[nalc472]

Why did U not try the lower NC channels?

 

[Bryan V]

I did. I guess I didn't explain it well. There was very little difference between all 11 channels.
8 and 10 gave the best VID. 9 hit the hardest audibly when swept North and south.
Channel 3 was the only one to give a constant one way hit going east and west.
All other channels gave only occasional hits sweeping east and west.
All channels hit the 10" dime sweeping North South but channel 9 hit the hardest.
It is the channel the Etrac chose when I did a noise cancel.
All these results I am talking about were very subtle but if I had to pick the best channels
it was the upper ones from 9-11 with the exception of channel 3.
Bryan

 

[IDXMonster]

I'd imagine, in an absolutely EMI-free area, the different N/C channels COULD give better performance. Most of the time it's about FINDING a good hit in the first place, which is infinitely more dependent on technique, site selection and coil choice.

 

[nalc472]

Better performance to find silver. Lower freq=greater silver count. Whether it would be deeper with a lower freq is possible in theory but who knows in practice. An Am signal will travel farther around the earth than a FM signal because a Fm signal is a higher freq. The higher freq is a shorter wave. It cannot travel as far. A Am signal is a longer wave form. Thus can travel greater distance. Same way for 5khz vs 22khz. 5 khz will go deeper in theory. Makes sense to me. WOrked in the signal analysis for 7 years.

 

[IDXMonster]

Better performance to find silver. Lower freq=greater silver count. Whether it would be deeper with a lower freq is possible in theory but who knows in practice. An Am signal will travel farther around the earth than a FM signal because a Fm signal is a higher freq. The higher freq is a shorter wave. It cannot travel as far. A Am signal is a longer wave form. Thus can travel greater distance. Same way for 5khz vs 22khz. 5 khz will go deeper in theory. Makes sense to me. WOrked in the signal analysis for 7 years.

Very true, the low KHZ seems to be the one for silver...and I'm all about that! Interesting stuff, any edge is an edge!