Nexus Coil Design

[Nexus]

I'd love to know what that was in English, 'cos I bet it wasn't a well done!

Hold up, YOU warned Dave Emery?????? Gerogi you are in danger of being branded an idiot coming out with statments like that. I used to respect your views, but you are RAPIDLY losing crediibility coming out with guff like that.

If you want to take part in a VALID conversation, perhaps you will tell us the WHOLE theory of operation and a complete explanation of your design, then maybe we can understand and give you the credit you may deserve, but slagging people off on this forum?? GO AWAY if that's all you want to do, we have a very friendly atmosphere here and respect each others skills and opinions.

You better show your self with your real name Sean Goddard.
How many companies have warned you with court cases by now for your redicilous claims?

[Nexus]

Pro4etoh podrobno tova koeto ste pisali vav foruma,i mnenieto mi za vas suvpada s mnogo ot tezi na drugite u4astnici vav foruma.Ako 6tete i super antena da slojite na kalpav priemnik-rezultata e sy6tij kato super priemnik s kalpava antena.Kato gledam shemite-tova sa ne6ta ot predi 10-15 godini i tezi shemi sa trugnali ot Shumen (az predi 10 godini sglobih takuv detektor i to4no v tozi grad,po-to4no povtorih edna shema s malko i zmenenij ot moj strana).A ima i dosta osobennosti po tezi shemi i podbora na komponenti,za koiro se pravjt otdleni shemi za izmervane na parametrite im.Ne te znam kvi gi vr6i6 i kvo se opitva6 da prodava6,no 4eteiki prikazkite ti ostavam s vpe4atlenie 4e si dosta bos na tema elektronika.Njma da ti pravj literaturno 4etene,no 6te ti kaja slednoto daje i tvojta antena s 14... i neznam si kolkoto tam grama e tejka!prdi 6 mesetza v BG vijdh PI detector s mnogo po-leka antena i s vazmojnosti to4no da razpoznava tipa metal,koeto si e edno seriozno postijenie i dosega ne sum vijdal druga takava shema.Shemata si e procesorna i ima dosta interesna shemotehnika i zamisul. Kolkoto do vidovete anteni-mnogo sa i vsjka si ima prednazna4enie,taka 4e ne se opitvai da se izkara6 genii kato si napravin ne6to koeto raboti i da se opitva6 da go probitva6 na horata tuk,i nai ve4e ne se pi6i velik profesionalist v oblastta si.Ne zabravji 4e "Titanik" e stroen ot profesionalisti,a Noj e bil amatjor!Tova e forum za obmen na techni4eski idei kakto vijdam,a ne za probutvane na metalodetektori.Kato iska6 da prodava6-pusni objva v njkoi BG forum i prodavai....

It is good manners that you write in english here. And it is very good manners to review all data availeble on the subjects.
This tread was not created by me. It was reported to me for the unfortunate incorect information posted by other Bulgarians.
I will not argue with you about anything.
Just bring your detector out to compare it with the Nexus.
And by the way did you see me offering detectors on this forum and when?
Here I only answer questions if anyone would ask and I do not try to provoke any jalousy outburst.
If you choose not to believe what I say, fine. You do not have to.
But at the least give the benefit of the doubght and take a chance to see first then talk.

[Nexus]

Let me see if I got this right...I'm an idiot in the shaddow of your greatness and I should keep my mouth shut, does that about cover it? Okay professor whatever you say. Your detector is the best and you are the Einstein of our age. I will look for you on the cover of Time Magazine.

No you are deffinitely not an idiot.
But just as definitely you are nasty in your atittude.
You do not have to be like that.

[Charles (Upstate NY)]

Professor Nexus I'm just having some fun with you because while you can design a detector you quite obviously lack the basic business and communications skills needed to sell one.

All you have managed to do in the last 24 hours is alienate me as a potential customer, that's the last thing you want as a business. Worse, I happen to have a rather large network of detecting pals both here in the states and abroad compounding the mistake. Worse still, I'll be attending the North/South Hunt next week with 230 detectorist from all over the US and Canada, can you guess what my feedback will be regarding the Nexus or more importantly the person who designed it?

Okay lets take your latest comments one by one...

>>>Your variety of shapes means very little when talking about results of how deep those can go.

Wrong! You sound like someone who has spent far more time at the test bench than in the field detecting. Target seperation has far more to do with making finds than raw depth. You attempt to simplify what is in reality a far more complex issue of soil conditions, moisture content, and the matrix of iron and trash we deal with on a daily basis. That your detector goes 3 feet deep means nothing if it can't get between the three pieces of iron that have been masking target A from other detectorists for the last 30 years.

>>>Just from the pics I can tell you that you have no chances to outcompete Nexus which is offered with one coil only, not 50 different ones.

Wrong! The only way you could make that statement with any credibility would be if you came over to New York and hunted next to me comparing my coils and the Explorer to the Nexus in a side by side field test on actual targets in the ground before they are dug, in our particular soil type and site conditions. Its the type of unsubstantiated, unscientific statement that gives me cause to doubt any claims made by such an individual. Pssst...I was building wide DD coils for my Explorer three years before your Nexus machine hit the market.

>>>but buddy those are copies of what other people have designed before you.

Wrong! Unless you have xray vision this statement is meaningless.

>>>The question is can you show something you have created which can demonstrate substantial advantages to the designs done before you.

If you had been visiting Geotech for several years as I have you would have seen them Professor, but you are a newbie.

>>>What about coming over here with your best detector and prove it against the Nexus in fair competition?

Uh, yeah you know that marketing 101 class you slept through, you may want to go back and take it again. I could care less how the Nexus performs 4,000 miles away. You bring the Nexus over to New York, we'll go jump into a 300 year old pile of rusty nails and nasty hot soil and trash. The Explorer is king in our local site condition, all newcombers can bring it!

>>>Remember well this. What you do has been done by many before you and after you, but the Nexus is quite unique by it`s capabilities.

Bring it over skippy.

>>>If you were inteligent enough could eventualy try to comprehend the possibility that someone out there has done something better. But that will require more of the science and not that much of the CNC`s and dozens and dozens of plastic bits.

See here's another example of that "insult the potential customer" style of yours that is not working.

>>>Why didn`t you think first about getteing in busness with me rather that being a smart ***.

What possible interest would I have in partnering with you? I have a $100k a year job so I don't need the money. You threaten to sue Dave Emery, an engineer that has gone out of his way to assist many of us on this forum. And you have an almost abrasive personality.

Regarding being a smart *** let me quote you, "It will be good if you can present your engineering work before placing expert statements." This is the statement which started the whole conversation in motion. Many people will read that and think now there's a snob who looks down his nose at others which is exactly how I took it. How dare you challenge me, I'm an engineer by god and you are a lowely ameteur, shut up and keep your place.

>>>This is forum about metal detectors, not heavy machinery. Show some detectors please. Will you?

Wrong! See the Tools and Technique forum bonehead, the Geotech owner created that forum just for me. And before you go an embarrass yourself again let me quote something Carl (the Geotech website owner) said recently...

"Building is coil is 97% mechanical, 3% electrical."

Well its been amusing bantering with you but I have better things to do. Good luck with the Nexus, you'll need it.

[Charles (Upstate NY)]

>>>I am not saying that Charles have done nothing, but his aproach to me was rude as from a great expert to an amature.

Professor Nexus come on now, it was you who was rude from the start not I. Here is my initial post...

"Correction, a gap is not required for graphite/carbon black shielded coils, at least not on the Minelab Explorer, Sovereign, Excalibur variety. Nor do the shields need to be electrically isolated from one another."

What may I ask is rude in that post? And mind you there are a number of people trying to build coils for Explorers and Sovereigns who visit this site so the correction was needed since your information was not accurate in regard to them.

Here's what happened, you did not like being corrected and so you responded with this rude remark,

"After all I have designed the deepest dtectors on the market. It will be good if you can present your engineering work before placing expert statements."

>>>And believe me he does not know as much as he thinks, other wise he would of understand.

I never claimed to know anything bonehead, you are the one coming across like some detector design god and telling people to "shut up".

>>>but I will not show any tolerance to nasty american attitude. OK

Ah see there's a bright idea, try to alienate the entire US market why don't you. Hey don't go away mad, just go away.

[Mike]

Confused

I'm not sure if this is a good time, but I'd like to ask a technical question.

Hi Nexus,

I have not built any TR/IB coils (yet), so forgive inexperience, but I have a couple of questions regarding one of your previous posts:

The main problem when shielding coils which will always occure is the offset valtage in the receive coil of the system, caused by this screen (shield).

Can this not be easily overcome? For example, if building a concentric coil, you adjust the bucking coil to null the received signal. Then you apply the sheilding (e.g. graphite paint, aluminium foil etc.) which upsets the null. But I understand that you can have a small loop of wire between the outer transmit and inner bucking coil, and you can move this around to get back to a null? Would this method overcome the problem? The small loop of wire would be unsheilded, but it's effect would be very small, so I guess it's worth it.

The best efficiency for two coils in induction balance will be acheiveble without any shielding, but unfortunately that arrangement will not work in real conditions.

I know that everyone uses sheilds on the coil, but why? It can't be anything to do with ground effects because the ground control takes care of that. It can't be because capacitive coupling causes the transmit oscillator to change frequency (a problem with BFO designs) which could cause apparent phase changes (I think), because that could be overcome by using a crystal controlled oscillator, unless sheilding is cheaper than a crystal controlled oscillator. I mean, what would the problems be with using a TR/IB detector with an usheilded coil?

Thanks,

Mike

[Carl-NC]

Gentlemen,

The purpose of these forums is to share information, and to occasionally enter into (hopefully) friendly discussions (OK, maybe even debates). The #1 rule is that these discussions be civil. Every person on this thread has been a positive contributor to the forums. Cut the sniping, or I will begin deleting posts.

Thanks,
Carl

[Charles (Upstate NY)]

Will do Carl!

[Nexus]

Shielding coils

The overcome of the offset problems is not a challenge if the RX coil is not tunned in resonance to the TX coil. In that case any type of shield will be easy to use and the balance easy to acheive.
If aluminium foil is the material for all shields on all coils in a search head, then is essential to screen each loop separately, the TX, the RX and the feedback loop as well. That will provide maximum protection from external interfearance and minimum antenna efect.
If a graphite paint or nickel compound are used in this case they can be applied on two plates on both sides of the coil system. Only keep in mind that for this design solution the specific resistance of the screening plates should be relatively high (100-500 Ohms per inch).




Shield on the coils is very important especialy on the receiving one. The ground ballance controls can sort out only the problems with the incomming trough the RX coil amplitude and phase changes caused by the ground minerals. The other main problem which unshielded coil would face is the capacitance occuring between the ground surface and the coil it self. For the transmitting coils that is not nesesary a bit problem since most of them a driven by stable enough oscilators, but fot the receiving coil it is. If the capacitance between the ground surface and the RX coil is not eliminated completely that will result in numerous false signals caused by the random changes of the ground surface. In case like this the parasitic capasitance from the ground surface will cause phase shift and amplitude changes in the RX coil which will appear as multiple metal targets. That will eventualy turn the work with such a detector in real hell.
For this reasons the Rx coil has to be properly shielded, regardless.

PLEASE NOTE THAT THIS COMMENTS ARE ONLY REGARDING CASES WHERE THE TX COIL AND THE RX COIL ARE NOT TUNNED IN FULL OR PARTIAL RESONANCE TO ONE ANOTHER.

Tunning coils in full resonance will normally require years of experiance and a lot of knowlege in coil theory and theoretical mechanics in order to acheive good and durable results.
Good luck.

[Mike]

OK

That is very interesting. Now you've explained it, I can see how ground capacitance can change the phase and amplitude of the received signal.

You said:

The overcome of the offset problems is not a challenge if the RX coil is not tunned in resonance to the TX coil. In that case any type of shield will be easy to use and the balance easy to acheive.

Looking at the Tesoro Bandido schematic, and the page with search head parameters, posted on Geotech's main site, the Tx LC oscillator resonates at about 10kHz, whereas the Rx LC is tuned to about 11kHz. I'd not really understood why the Tesoro engineers had done this, but your comments above give an explanation. They wanted a coil assembly that was easy to tune and screen.

I bet the Nexus Tx and Rx coils are tuned in resonance, and that's why it's so sensitive?

[Siliquae_Sid]

Yes my real name IS Sean Goddard and I'm not afraid of you or ANY of the pathetic detector manufacturers out there, Bring it on buddy, You, Lamebin, Fisher, Garrett, Tesoro are nothing!! The detector market is too small to be taken seriously by the law.

I do not make false claims, I point out the feebleness of those who make claims they cannot substantiate and the bullS**t the is prevalent in this industry.

FYI I have not called you or the Nexus by any insults, nor have I EVER said it did not live up to the claims you made. In fact I a have witnessed one in action, and was very impressed. I have supported you by telling many others how good this machine is (Ask Gary), and now you insult me, yes you are a REAL man aren't you for that?

Sorry Georgi, but you DO seem to have a I'm the greatest attitude and it's laughable. Yes you may be a great Engineer, but from your comments you look childish. PLEASE stop being so arrogant, it's only making you look silly. I make no suchc claims nor have I EVER said I was better, All i have ever said is thet modern detectors COULD BE BETTER. If that's a ridiculous claim, then you are in there with me making it boy!

Where once I had a lot of respect for you, but after your purile tirade against Charles and others on this forum, Now I'm not so sure.

Thanks by the way, for explaining your theories, very good , now maybe we can start having a meaningful discussion with no more "I'm better than you" attitudes in them. ;-)

[Cesar]

Come on guys i´m trying to learn something here and what i get is another cold war, all i heard is good things about the Nexus congrats to the designer,........, also Charles makes the best coil shells in the market today,......, congrats to you too bud !
So lets all be friends and start over from the begining,......we need all the feedback we can get from everyone´s experience on this area !

Cesar

[Siliquae_Sid]

I agree Cesar!! How about it Georgi.. I'm up for a friendly discussion about coil design and your theories. Could you post some math maybe?

[Nexus]

That is very interesting. Now you've explained it, I can see how ground capacitance can change the phase and amplitude of the received signal.

You said:

Looking at the Tesoro Bandido schematic, and the page with search head parameters, posted on Geotech's main site, the Tx LC oscillator resonates at about 10kHz, whereas the Rx LC is tuned to about 11kHz. I'd not really understood why the Tesoro engineers had done this, but your comments above give an explanation. They wanted a coil assembly that was easy to tune and screen.

I bet the Nexus Tx and Rx coils are tuned in resonance, and that's why it's so sensitive?

The Nexus coils are tunned in full resonance within +/-1% tolerance.
The well known manufacturers arround the world do not manufacture resonance tunned coils for various resons, but the most important of all is costs.

[Siliquae_Sid]

I was told this caused phase linearity problems and thus made accurate discrimination almost impossible. If you have found a way of getting around this then can you explain how you have done this, and the principles and reasoning involved.