Tx and Rx coil inductance ratio

[Qiaozhi]

I don't think so Mr Davor . I never seen a VLF coil bigger than this one [ATTACH]46723[/ATTACH].

In that case, try these ->
https://www.nexusdetectors.com/after...archcoils.html

[ifrenide]

WoW ! It is really huge coil . But not 4 meter of diameter of course or even 1 meter .

[WM6]

WoW ! It is really huge coil . But not 4 meter of diameter of course or even 1 meter .

What about so called "Ground Loop" coils:




Applied to PI for now.

[Nexus]

WoW ! It is really huge coil . But not 4 meter of diameter of course or even 1 meter .

The Nexus 41"CC is 104 cm in diameter.
There is an older model that was made only for few customers with a figure of 8 or dual 1 meter coil (185cm x 100 cm) - Nexus Exselsior.
Now the 41"CC will be manufactured for Minelab GPX.

For anyone who would be interested.
Nexus coils are all made with equal ration TX to RX number of turns, equal inductance ect. I found it a waste of time to do coils with different ratios as just like Carl mentioned the increase of sensitivity is not only to targets, but to ground as well.
The best "transformer" connection between TX and RX is a full resonance and of course the best possible sensitivity to derive from any coil. A fully tuned in resonance coil will replace about 20 times of the input gain, meaning the input stage will need 20 times less gain compared to the use of a RX coil not tuned at all.
I hope this helps.

[Nandor]

Thank you for sharing this information about you coils!

[ifrenide]

Hello.
If your opinion is wrong, each time you attempt to support it, for sure you will make another mistake.You can know if you're wrong or far from the truth by looking at you examples "exceptions, unpractical,not popular".

-WM6 my brother. you show as a picture"not real picture" of unpractical device, so each time I want to test a place, I have to move the big coils and the 2 units.there is other technical problem.how to make them working together in armonic way,I mean you play around microseconds.how we make a separate receiving unite, get the signal of a target just a moment when the transmit signal is off ????? in a one unit yes "easy".finnaly this is a PI metal detector.different from VFL system.
Nexus
my brother.your coil is an exeption and you said : "that was made only for few customers" you know why , because it is unpractical and sometimes you can find some people like testing and trying some stange stuff "the world's biggest VLF coil" we love unusual things. you said :" like Carl mentioned the increase of sensitivity is not only to targets, but to ground as well" I respect him, of course he's the lion here . but I want tell something mybe I'm wrong. If if we get a high sensitivity for both ground and target, we stand and watching them? no,we will solve this problem by using electronics" make a good ground balance system".
in theory making a big VLF coil is a true fact .un practical if we take in consideration sweep speed of coil and human force to match this speed, and there is a problem when we want to take this coil with as "it's too big ".we need a truck to make metal detecting so! .Without talking about effeciency. it's like you bay a bus instead, of car. and you bay it for personnel use . you can use it but, look around you .only cars is used for personnel purposes.

[Nexus]

Nexus
my brother.your coil is an exeption and you said : "that was made only for few customers" you know why , because it is unpractical and sometimes you can find some people like testing and trying some stange stuff "the world's biggest VLF coil" we love unusual things. you said :" like Carl mentioned the increase of sensitivity is not only to targets, but to ground as well" I respect him, of course he's the lion here . but I want tell something mybe I'm wrong. If if we get a high sensitivity for both ground and target, we stand and watching them? no,we will solve this problem by using electronics" make a good ground balance system".
in theory making a big VLF coil is a true fact .un practical if we take in consideration sweep speed of coil and human force to match this speed, and there is a problem when we want to take this coil with as "it's too big ".we need a truck to make metal detecting so! .Without talking about effeciency. it's like you bay a bus instead, of car. and you bay it for personnel use . you can use it but, look around you .only cars is used for personnel purposes.

When someone states that big coils are unpractical that tell's me one thing - the person behind the statement knows little or nothing about big coils, how do they work, how to use them and what they are good for.
The Nexus Exselsior was sold to only few customers, because I do not want to market this model. It takes months to manufacture one and it is more profitable to make and sell smaller detectors. That detector was developed by request from customers in the first place. So do not be in a hurry to believe in wrong conclusions.

The bigger coils do exhibit more sensitivity to both ground and targets, however they also exhibit higher signal to noise ratio. This means that the ground noise by proportion is lower compared to the target signals, thus the better depth of bigger coils.
Big coils are less affected by the reactive component(ferro-magnetic) in the soil and more vulnerable to the active component (conductivity) of the soil in VLF only. This is why they work better in highly mineralised soil conditions compared to smaller coils and are somewhat more noisy on muddy soil, next to small coils.
However big coils are big and always get the deep stuff, no matter what. Well providing the operator knows why did he get the big coil in the first place and how to use it.

Since you use cars for comparative example let me give you one.
Ferrari is not much good off road, but it gets 300km/h easily where it counts.
Same with big coils. They are unbeatable where it counts.

[godigit1]

Is this a dual field coil?
Sure looks that way. ive thought this is the only way to do a monster coil.

[Nexus]

Is this a dual field coil?
Sure looks that way. ive thought this is the only way to do a monster coil.

It is a concentric coil with TX outside and RX inside. It works like DD on GPX, just the RX is much smaller. The purpose is to have the power output of a Mono coil and some discrimination abilities as DD. For a given size Nexus concentric coils are also more sensitive to small objects compared to Mono and DD equivalents when used on ML GPX detectors.

[ifrenide]

When someone states that big coils are unpractical that tell's me one thing - the person behind the statement knows little or nothing about big coils, how do they work, how to use them and what they are good for.
The Nexus Exselsior was sold to only few customers, because I do not want to market this model. It takes months to manufacture one and it is more profitable to make and sell smaller detectors. That detector was developed by request from customers in the first place. So do not be in a hurry to believe in wrong conclusions.

The bigger coils do exhibit more sensitivity to both ground and targets, however they also exhibit higher signal to noise ratio. This means that the ground noise by proportion is lower compared to the target signals, thus the better depth of bigger coils.
Big coils are less affected by the reactive component(ferro-magnetic) in the soil and more vulnerable to the active component (conductivity) of the soil in VLF only. This is why they work better in highly mineralised soil conditions compared to smaller coils and are somewhat more noisy on muddy soil, next to small coils.
However big coils are big and always get the deep stuff, no matter what. Well providing the operator knows why did he get the big coil in the first place and how to use it.

Since you use cars for comparative example let me give you one.
Ferrari is not much good off road, but it gets 300km/h easily where it counts.
Same with big coils. They are unbeatable where it counts.

1-you told me that I don't know how big coils work,you can just say how VLF coils work , you specified them here as they work differently.do you think that work with a different way?.
2-you think I don't know how to use a big coil. so if we have a big coil .I can't use it like usual ones the bigger coils have special manipulation? .my brother we use all coils the same way,we keep a small space between the coil and the ground and we seep it "explanation for aliens, I think they don't know how to use a coil".
3-what they are good for? when I meet Aliens ,I will tell them" its complicated you have spend years and years to understand why we use a big coil".
4-you said" I do not want to market this model. It takes months to manufacture one".I don't think that you are manufacturing a rocket .takes months,come on man.
5-you said :" it is more profitable to make and sell smaller detectors".all this detectorists.they don't know what is the good thing for them unfortunatelly.hey man there something let them go to choose smaller coils. you have to find it. I can't repeat it.
6-you said"That detector was developed by request from customers in the first place". I think this company should take the initiative and lead customers,and don't be passive regarding inovation.
So do not be in a hurry to believe in wrong conclusions from you,to you .
7-you said:"The bigger coils do exhibit more sensitivity to both ground and targets" this is a passive point of view "this is what happen",the truth is that we can be active and treat this problem with electronics and "change what's happening".this is the golden rule . vintage detectors haven't a lot of features which exist now days.
8-you said:"however they also exhibit higher signal to noise ratio. This means that the ground noise by proportion is lower compared to the target signals, thus the better depth of bigger coils."So you think that detection depth of big coil is a result of that the ground noise by propotion is lower tha target signals, are you serious? not eddy currents are propotional to electromagnetic field power.of course with taking care about parasitic factors,and how good our electronic system ,in terms of effeciency?
9-you said:"Big coils are less affected by the reactive component(ferro-magnetic) in the soil and more vulnerable to the active component (conductivity) of the soil in VLF only. This is why they work better in highly mineralised soil conditions compared to smaller coils and are somewhat more noisy on muddy soil, next to small coils.
However big coils are big and always get the deep stuff, no matter what. Well providing the operator knows why did he get the big coil in the first place and how to use it."you are talking about a result and not about the reason "Big coils are less affected by the reactive component(ferro-magnetic) in the soil and more vulnerable to the active component (conductivity) of the soil in VLF only " this is a result and not a reason.try to find, the reason behind that.
Finaly the example of cars is to highlight the portability,and not the speed.
nice to contact you nexus.we are brothers .

[Hyena]

What is the weight of these beautiful monsters?

30 inches / 75 centimeters; Approx 1095 means grams?

What is the weight of 21" coil and 41" coils?

[ifrenide]

Hello hyina, I think 21" coil weigths : 21"/30"*1095grams=766.5 grams . for 41" coil it is: 41"/30"*1095grams=1496.5 grams .I just guessed !

[Nandor]

I've tried different value resistors for TGSL front end. As the resistor values gets smaller than the original 4k7 the Rx signal gets more noisy and less in amplitude with the same gain ratio of 47x aprox. I tried 1k-47k, 2k2-100k but the best was with 4k7-220k.

Does the coil gets loaded if the resistor value gets smaller, could somebody explain this?

[dbanner]

I think 5.1K @1% was the stated value on the bill lahr schematic(tesoro golden sabre). TGSL schem was derived from original, but a few part values were altered slightly.
All these tesoro circuits ( silver sabre, golden, pantera, el dorado, royal sabre, bandido) use 5.1K. The lobo is different because the inductance of the RX coil is different.
The rx inductance for original coil is about 6.2mH, uses a 5.1K resistor. The TGSL build document states the rx coil at 6.5mH, using a 4.7K resistor. So there you have it.

[Nandor]

I have many Tesoro schematics, as you say they are almost the same. Some time in the past I was browsing the TGSL topic and it was a post about coil loading, but then I did not understand electronics as much. I would like to find out what it does mean and how to avoid it.