Emi Vs Smf

[HardPack]

8 hours ago, Digalicious said:

Was that low iron bias deliberate for some reason, or do you normally run the IB as high as necessary to avoid iron falsing?

There is rusted tin everywhere, layered as if they ran it through a wood chipper before spreading. Plus flatten rusted tin cans, rusted square nails, rusted sheets, cast iron you name it. That why l was using ground tracking,  there no areas free of rusted tin to pump the coil. So to deal with the EMI and to get a rough idea of detection depth I kept Recovery & Iron Bias low but ran only the Sensitivity up. I was able to cut a few non ferrous targets out of the dirt. 

[HardPack]

Took the EQX 900 & 11 inch coil out to the EMI field of rusted dreams. In Park 1 started with single frequency 5 kHz, Recovery 4, Iron Bias 2. After Noise cancelling checked for EMI.  Was able run the Sensitivity to 24 then 26 then 28. Little or no EMI. Ran the Recovery to 6, Iron Bias 4. Dug all targets to check detection depth pulled the upper portion of a rusted square nail at 8 inches. 

Switched to Multi-Frequency, Field 2, Recovery 3, Iron Bias 1. Noise cancelled then adjusted Sensitivity 22, 24 then settled on 26. Little or no EMI. Adjusted Recovery 4, Iron Bias 2, Sensitivity 26. Dug several more rusted square nails at 6 to 8 inches, several shallow boot tacks, shotgun brass.

While running in discrimination I use the random TID spread of the false positive signals to identify buried iron. I may switch to All Metals to verify if in doubt. The TID numbers for 22 brass and lead are consistent enough that I no longer dig. Non-ferrous target signals jump out of the layered rusted iron. The EQX stock 11 inch is not as precise as the Coiltek 10x5 but sure operates far smoother in the presents of EMI. 
Also switched to the gold modes, lowered volume & sensitivity but still too much EMI interference.

Discovered an old tent site perched up on the end of a rocky peninsula. The miners had removed the bench gravels on both the upstream and down stream side. A rock wall fire pit was all that remained setting 30 feet above bedrock along with two old pine trees. They did some nice stone work on the water ditch in this same area. Instead of piling rock next to the sluice runs it appears the mulchers pushed everything off the end into the creek bottom.

 

 

[JCR]

You might try NOT using Ground Tracking in that much Iron trash.   I have never had good results doing so. The detector gets confused and it just adds extra noise and can cause target masking. If you can, find a clear spot off site that has the same type of soil,  even setting it to Zero would probably be an improvement over Tracking.

[HardPack]

1 hour ago, JCR said:

If you can, find a clear spot off site that has the same type of soil,  even setting it to Zero would probably be an improvement over Tracking.

I have been monitoring the ground tracking numbers, between 39 & 40. I can set the GB manually. Already have the stock 6 inch coil ready for a run early next week if the weather holds. I’ll try pumping the coil then adjust if necessary.

You got me thinking now. Whether ground tracking or pumping the coil over a carpet of rusted iron the detector is attempting to cancel all the ground noise including the buried iron under the coil. Even if completely successful the iron false positive signals are still going to bleed through creating a constant back ground noise. Plus the initial ground balance number will be off, probably on the high side. You’re right I need to bring the rake. Thanks for the advice.

[HardPack]

One more EMI trip. This time with the Nox 6 inch coil on the EQX 900. Used Auto Ground Balance (39-40 GB); stayed in Multi-Frequency in all search modes; Sensitivity 26. Same smooth results as with the Nox 11 inch in Park 1/2 and Field 1/2 modes. Dug two shallow modern dimes.

In Gold modes 1 & 2: Multi-Frequency, Auto Ground Balance (different area same site 54 GB), Sensitivity 18, Volume 12, Recovery 1, Iron Bias 0, Threshold Level 12, Threshold Pitch 11, Target Tone 1, Accept/Reject -10 to 0, 1 to 99. No headphones, Smooth Threshold, no EMI, rejected TID -19 to -11 due to the excessive site ground signals in this range. 

Coil recap: with all search modes in Multi-Frequency: Coiltek 10x5 Nox very susceptible to EMI especially in the Gold modes; Nox 11 smooth in Park 1, Park 2, Field 1 & Field 2; susceptible to EMI in both Gold modes; Nox 6 smooth in all search modes. Ground tracking and Auto Ground Balance numbers were similar (39-40 GB).