Combating EMI

[Azoverland]

I am constantly combating alot of EMI noise with my machine, GPX5000. Even in the most remote areas and even at night the detectors threshold becomes unstable quickly.

In this video at the 2:00 mark there is great info on detector noise. Using the test with a mono coil and switching the detector to cancel the threshold is smooth and quite, so it is not detector noise.

http://www.minelab.com/usa/videos?id=32739

Thanks JP for posting the video in the Blitz Coil thread about ground balance. It's a great and simple reminder of how to really balance any coil and following these instructions I have seen an improvement in how well I am ground balanced. But the problem I am having is not ground balance.

I have never been able to find a channel and use it all day. I will start by auto tuning the detector and if the channel is still too unstable (which is often the case) I will manualy tune to a channel that sounds better to me. However I am doing this very often and still getting alot of noise from EMI. In some cases I simply can not use a larger Mono coil. I have to use a DD coil or a small CoilTek Joey or the threshold is so unable I may as well be in my livingroom. But that is not based on location. I have been in the same area (with in 100 yards) one day and the threshold is smooth and the next day or 20 minutes later it is junk?

Two things I have NOT done that are outlined in the Owners Manual:

1. Change the Coil switch to Cancel and then retune the detector if necessary

2. Select Fast motion before the Auto Tune process

I'll try these out this weekend and see if it helps......

In all I have read or the videos I have seen the answer seems simple. Use auto or manual tune and tune it out, but that's just not happening. Any ideas or help on this would be greatly appreciated.

[goldnomad]

Two things I have NOT done that are outlined in the Owners Manual:

1. Change the Coil switch to Cancel and then retune the detector if necessary

2. Select Fast motion before the Auto Tune process

I'll try these out this weekend and see if it helps......

Hi AzOverland

It also helps to turn up the "Gain" to it's maximum as well as 1. and 2.

Cheers

Robert

[Reno Chris]

You didnt say what setting your are putting the gain at.

Setting the gain too high maximizes the effects of emi. Just like if you turn a radio to a spot between stations and turn up the volume to maximum - you hear a lot of static. At the volume which you might normally listen to music or talk, the static is not normally a big deal.

In addition to what it was designed for, your detector is also an emi receiver - and the coil is its antenae. You may have to turn down the gain a bit to get a better threshold without the EMI interference.

Chris

[DolanDave]

Like Reno Chris and Goldnomad say, check the RX gain, I always have to adjust my gain, even when I am hunting the same area. I noticed a lot of times in the morning I can crank my gain higher, towards the afternoon, and late afternoon I have to turn it down as the EMI increases or decreases during the day.

[Azoverland]

A number of times I have reset the detector to factory setting and continue to have the issue. I don't ever run the gain over 14 if I do adjust it at all which is not often. I have found the factory setting seem to work best for my skill level and with the total of 6 search modes and 8 timings I haven't had enough time to explore all of the factory options really.

[Reno Chris]

A number of times I have reset the detector to factory setting and continue to have the issue. I don't ever run the gain over 14 if I do adjust it at all which is not often. I have found the factory setting seem to work best for my skill level and with the total of 6 search modes and 8 timings I haven't had enough time to explore all of the factory options really.

Just as a test, try running the gain at 8 and see if it isn't a lot more stable.

Quoted right from the manual itself:

"A lower Rx Gain setting is preferable for variable, ‘noisy’ conditions or high interference areas."

The only time I have hunted down near the border (isnt that where you are?) the feds had all kinds of radio based people detecting units out and about down there. Might be a source of way excesive EMI. (though I dont remember it as excessive the day I was there ).

Chris

[Jonathan Porter]

Hope this helps,

JP

[Jonathan Porter]

A number of times I have reset the detector to factory setting and continue to have the issue. I don't ever run the gain over 14 if I do adjust it at all which is not often. I have found the factory setting seem to work best for my skill level and with the total of 6 search modes and 8 timings I haven't had enough time to explore all of the factory options really.

What Motion setting and Audio filter are you using?

JP

[Azoverland]

Just as a test, try running the gain at 8 and see if it isn't a lot more stable.

Quoted right from the manual itself:

"A lower Rx Gain setting is preferable for variable, ‘noisy’ conditions or high interference areas."

The only time I have hunted down near the border (isnt that where you are?) the feds had all kinds of radio based people detecting units out and about down there. Might be a source of way excesive EMI. (though I dont remember it as excessive the day I was there ).

Chris

Yea we're swinging in between Border Patrol trucks and some air traffic down here alot but not always. But I was hoping to tune that out. I guess a RX Gain deduction is in order. I will try it out.

[Azoverland]

What Motion setting and Audio filter are you using?

JP

Motion is slow or very slow most of the time. I not sure what you mean by audio filter?

[Jonathan Porter]

Motion is slow or very slow most of the time. I not sure what you mean by audio filter?

Deep, Normal, Boost or Quiet under Audio in the menu.

JP

[Azoverland]

Deep, Normal, Boost or Quiet under Audio in the menu.

JP

Never played with it. Just the factory sets. Deep in Deep and Normal in General search modes is where I spend most of my time in. Why do you ask and thanks for the input. I also hunt in Patch a little which is Normal. I have just never paid attention to this setting really???

Edit:

Ok read about audio filters in the manual.

Looks like the lessen EMI after the Auto or manual tune process. You can -

1. Lessen the RX Gain

2. Use Slow or Very Slow sweep speed

3. Select Quiet audio type

Thanks again guys

[El Dorado]

At the ICMJ Summit, Kevin H. explained a unique way of tuning the detector. First, put it in patch mode with the gain at max. Now do a normal tune with the coil pointed towards the most interference. Note the frequency of the what the machine picked. Now, tune the machine a second time and note the frequency. Split the difference and then do a minor manual tune from there if needed....... It works well! He explained this method is not in the manual because the brainy guys at Minelab cannot prove why this works.....

[goldnomad]

Hi AzOverland

It also helps to turn up the "Gain" to it's maximum as well as 1. and 2.

Cheers

Robert

I forgot to to say to reset them back to your preferred settings after balancing but I guess you knew that

Robert

[Reno Chris]

Another quickie test just to see how much EMI you have is to just lift your coil up until its perpendicular to the ground and see what difference that makes. With ground based EMI sources your should hear a HUGE increase in EMI noise as compared to what you heard when the coil was in its normal position parallel to the ground. I sometimes do that when in the field just as a rough and dirty reference to see how bad the EMI really is.

(If your source is overhead, that method wont work, but the majority of the very worst EMI contributors are ground based)

Chris

[explorer1]

Az

Try going back to your original settings before this threshold problem started. But try it out some 10 miles or more away from the border. Dep't of Homeland Security is working with certain types of electronics at the border. "IF" you are to close, that could cause a problem. Best to do a process of elimination to rule it out.

Explorer

[Azoverland]

At the ICMJ Summit, Kevin H. explained a unique way of tuning the detector. First, put it in patch mode with the gain at max. Now do a normal tune with the coil pointed towards the most interference. Note the frequency of the what the machine picked. Now, tune the machine a second time and note the frequency. Split the difference and then do a minor manual tune from there if needed....... It works well! He explained this method is not in the manual because the brainy guys at Minelab cannot prove why this works.....

Thanks for all the info and replies guys.

What El Dorado said works VERY well. Today I got the best thershold I have had yet.

I switched the detector to Patch turn the RX Gain to max and the sweep speed to Fast(it does work better when the motion is switched to Fast). I pointed the detector in the direction of the most EMI and auto tuned. I noted the channel, 179. I repeated the process right away leaving the RX Gain at max and sweep speed at Fast and the auto tune then selected 238. I then manually selected 208 - listended and adjusted it up to 209. Reset the RX Gain to the preset and the sweep speed to slow. SMOOTH AS CAN BE.

I had to do this twice over the course of about 6 hours but it really works well in an area with alot of EMI.

[montana]

AZoverland. I always use veryslow sweep speed, and always use Quiet audio setting and rarely go above 10 on the gain. I never have trouble getting rid of the EMI. You can also reduce EMI with the stabilizer set to 7 or 8. ---Bob