Deus, TX Power, and EMI

[BobTheDigger]

I went to a spot that I have done good at but you cannot get any closer to the road then about 50ft, then the EMI takes over. I've been there with the Deus a few times before and tried a few different thing but couldn't get it stable enough to detect closer to the road. I was able to quiet it down a bit in frequency 18k but it was still too annoying to detect. I was more determined today to detect closer to the road so I figured I'd go through each and every setting to see if anything would work. I love how much you can fine tune the Deus and I knew there had to be a way to beat the EMI. As soon as I adjusted the tx power to 3 the EMI was virtually gone. I continued to play around with the settings a bit and as long as I had the tx power on 3 it seemed to be stable. There was some chatter in freq 4 and 8k and almost no chatter in freq 12 and 18k. I also noticed in tx power 3, 12k - it doesnt go crazy when I turn the pro pointer on (i hate when it does that). Im not sure if this will work in all EMI situations, just thought I'd share.

Anyways, I worked a small grid in the area I couldnt detect before and got a couple of rosies and some other goodies.

 

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[Calabash Digger]

thats wild I thought it would be just the opposite the higher tx worse emi but that goes to show you never know. thanks for sharing that trick.

 

[rick67]

I haven't had the problem with the pointer yet. I've heard others say that to. I'm still using the older garret pointer when on land.
Man you got Colonial with a corkscrew shank and Zouvie buttons roadside. Good luck conquering the area near that road.

 

[Calabash Digger]

congrats on the finds too. I have one garrett pointer its fine and another the same model carrot and it drives my machine crazy in 12 kh. I called garrett and they said the frequencys varie pointer to pointer so one of mine over laps just enough to drive my detector crazy.

 

[Deft Tones]

Awesome you got it hunted! I have a hillside next to powerlines I hunt. The EMI is bad at street level but I can still hunt with problems (not just a Deus problem here). As I move up in elevation parallel with the transmission lines, yet the distance has actually increased and the machine is all but useless. I wonder what the deal is with that?


Can someone explain how increasing the TX to 3 manages the EMI and what the effects are on sensitivity and depth? Also, what happens when increasing to TX3 in mineralized soils or in high trash/iron?

Any speculation?

Just trying to learn the Deus again, thanks.

 

[vferrari]

Increasing TX3 to solve the EMI, is a mystery to me from an electrical standpoint. EMI is a tricky thing, and sometimes it just takes trial and error or a small change in the resonant frequency of the circuit to make a difference, who knows. Perhaps the higher power demand changes how it behaves. But if it works, great - then have at it. I am going to have to try that one near my power line problem to see if it makes a difference. As far as TX power in setting in mineralized soil. According to Andy Sabisch, the guru of deus gurus (I figured you like that one Deft Tones), high TX power in mineralized soil is like high beams in fog. The higher power transmitted into the ground gets scattered more and ends up doing more harm than good on detection depth. So the rule of thumb is to back off to at least TX power 2 in mnineralized soil and 1 if highly mineralized per the mineralization bargraph. Not sure TX power makes that much difference in trashy soil. Reactivity/recovery speed is the key parameter in trashy soil. You want the machine to hit on that good target amongst the iron/aluminum trash and not recovering from that strong trash signal.

 

[Deft Tones]

Thanks Vferrari. I appreciate your humor and laid back style. (Touché - another French word!)

If the Deus acts like other conventional VLF detectors, then I would expect the increase to TX3 for EMI mitigation to make performance worse - increased chatter. ( But hey, whatever works, right?) If it does work then I would tend to think the EMI is being drown out enough to allow use at a cost of reduced performance in sensitivity and depth.

As far as high TX on the mineralized soil and trash/iron question, I was being a bit facetious. (French word again!) I wanted the information posted but I didn't want to be the one to do it. Thank you.

You're a scholar and a gentleman.

 

[vferrari]

Thanks Vferrari. I appreciate your humor and laid back style. (Touché - another French word!)

If the Deus acts like other conventional VLF detectors, then I would expect the increase to TX3 for EMI mitigation to make performance worse - increased chatter. ( But hey, whatever works, right?) If it does work then I would tend to think the EMI is being drown out enough to allow use at a cost of reduced performance in sensitivity and depth.

As far as high TX on the mineralized soil and trash/iron question, I was being a bit facetious. (French word again!) I wanted the information posted but I didn't want to be the one to do it. Thank you.

You're a scholar and a gentleman.

Thanks. Yeah the TX3 to lower EMI is totally counter-intuitive, but I have given up reconciling the rules of physics with metal detecting. It's whatever works, baby!

 

[HuntinDog]

Bob the digger,
I found that you my need to hunt your high EMI spot at night or VERY early in the morning. Before sunrise.
I have a place that I could never hunt with high EMI.
Tried all times of the day. I picked out a few coins every once in a while, but just couldn't get past the EMI.
One time I was returning home from a distant hunt and was driving by this spot at 1:00 in the morning and thought what the heck.
It still had EMI, but was low enough to hunt and I scored a nice batch of 1800s coin in about half hour of hunting.
Just a thought....

 

[Deft Tones]

I'll say what I have noticed having the greatest EMI mitigating effect is reducing reactivity to the lowest setting. Makes a huge difference inside my house, which is pretty bad for EMI.

 

[vferrari]

I'll say what I have noticed having the greatest EMI mitigating effect is reducing reactivity to the lowest setting. Makes a huge difference inside my house, which is pretty bad for EMI.

Yes, should have mentioned that previously. Another, reason I will likely not achieve guru status.

 

[austin_luker]

Posted this the other day, you were thinking the same as me!

Let me clarify I have a permission for a 1735 home site in NY. All the wars America has ever fought somehow or another went through this area so I am praying I pull some great relics and history! But when I did a quick test of the ground I started with the "sifter" program which runs 18K so I would have thought it would be the best Freq to use. But boy that B*itch was talking back mostly when the coil was stopped when you start moving she shuts up a little. I tried all the factory settings they all chatted just as much, my 0 disc deep full metel program was loud! I got freaked being new to the Dues and stopped at a park just to get away from all EMI, low and behold she was still chatting not as much but a constant coversation none the less. Now I'm really freaked thinking great I just bought this crap detector!! On the way home I stop at a old pull off in the woods no power lines or EMI for 200 yards or more, pull out the dues put on the loudest EMI hunting program I have. Well who would have thought "I could hear french crickets" not a peep! Pulled a old rifle cartrage that rang in at 82-83 and was deep about 8-9 inches. So I must conclude that the Dues is very good at hunting down any type of EMI if it's around you'll hear it.

 

[vferrari]

Posted this the other day, you were thinking the same as me!

Let me clarify I have a permission for a 1735 home site in NY. All the wars America has ever fought somehow or another went through this area so I am praying I pull some great relics and history! But when I did a quick test of the ground I started with the "sifter" program which runs 18K so I would have thought it would be the best Freq to use. But boy that B*itch was talking back mostly when the coil was stopped when you start moving she shuts up a little. I tried all the factory settings they all chatted just as much, my 0 disc deep full metel program was loud! I got freaked being new to the Dues and stopped at a park just to get away from all EMI, low and behold she was still chatting not as much but a constant coversation none the less. Now I'm really freaked thinking great I just bought this crap detector!! On the way home I stop at a old pull off in the woods no power lines or EMI for 200 yards or more, pull out the dues put on the loudest EMI hunting program I have. Well who would have thought "I could hear french crickets" not a peep! Pulled a old rifle cartrage that rang in at 82-83 and was deep about 8-9 inches. So I must conclude that the Dues is very good at hunting down any type of EMI if it's around you'll hear it.

And as was posted before, you can make some adjustments as suggested and tune out the EMI (adj frequency, etc.). You never said whether that helped. Yes the DEUS can be hamstrung by EMI, just like any other detector. And, yes, it can be really bad. But I also think there are very few detectors out there where you can adjust as many parameters (Frequency, Sensitivity, Reactivity, Silencer, TX Power, etc.) as the Deus to try to minimize the EMI. Otherwise, I think I may be missing your point.

 

[vferrari]

I'll say what I have noticed having the greatest EMI mitigating effect is reducing reactivity to the lowest setting. Makes a huge difference inside my house, which is pretty bad for EMI.

I just realized something and should have pointed it out sooner. If you merely adjust reactivity to 0 or 1 without making any other adjustments, silencer will automatically default to 3. So what you are essentially doing by just adjusting reactivity to a lower setting is just increasing silencer setting which is probably having the most effect on reducing the EMI (but with a huge hit on depth performance) than the reactivity setting itself. The Default Silencer Settings for each reactivity setting are given below:

Reactivity/Silencer
0/3
1/3
2/2
3/2
4/1
5/1

After a reactivity change, silencer will default to the above values unless you go into the Expert setting and readjust to your preferred silencer setting (Typically -1 or 0 for max depth) otherwise if you are having EMI issues you can push it higher (1 or 2) but depth performance will suffer. This is one of those quirky, undesirable Deus menu behaviors I was hoping would be resolved in Ver 4.0. HTH. HH.

 

[Iron Buzz]

Bumping this two year old thread because it fits well with something I just sent to a buddy that was dealing with heavy EMI at one of his sites.

gardansolyn is definitely saying to reduce TX gain. My logic, tho, is that it is like AM radio stations. A distant station that has a high transmission wattage will come in clear at a distance, even with the radio's volume (receive sensitivity/gain) low. However, turning up the volume (receive sensitivity/gain) on a weak distant station (low TX power) still sounds like crap, because the gain is increasing both the weak signal and the noise (EMI) equally. That is theory only, but you have to admit that it makes sense, anyway

I see some references above to TX power and soil mineralization and the "headlights in the fog" effect. True, but that is ground mineralization, not electromagnetic interference.