TESORO GOLDEN SABRE

[Fred]

Hi Ivconic,
Here XR2206 is still available (somewhat expensive),so if you need more and i can help you let me know.Same for LF353 :www leiritronica.com (its in portugal)
regards,
Fred.

[Max]

Hi
Again some theoric observation : It seem logical that coils shields MUST be isolated where they overlap,or else we are building small loops inside the coil , but i dont see anybody mentioning this.Is everyone isolating his shields?

regards,
Fred.

Hi,
yes we have explained a number of times I think... shields must be insulated at overlaps and then the only electrical connection is by their wires to gnd...so not in a closed path respect to coils.

If you overlap shields in a conductive way you create shorts around coils... the same if you don't leave the gap in each shield somewhere...

A large closed conductive loop will develop as much eddy currents that you'll easy saturate RX stage that way... and even if not totally saturated the RX stage of course this will destroy your SNR.

You need gaps and you need intershielding insulation: paper or some plastic tape is good at that overlaps.

Best regards,
Max

[ivconic]

I have XR2206 on my mind.It is obsolete and rare, but i still have one left in my scrap box...

[ivconic]

I understand what you're saying.
In the case of Fisher, Garrett, Whites, Minelab, however, they undoubtedly have a test setup in their individual factories for nulling coils, so (of course) all the coils they make for their machines will be the same, within certain manufacturing tolerances. Then when they design a new detector, it is designed to use the same coils. This just makes good economic sense. Then by default you can take an old Fisher coil and use it on a CZ5. Why not?

That is what i am trying to build these days! "Testing setup"! Osc.frq. should varry from 6kHz to 20kHz...Sinus and square at output. Adjustable amplitude...On RX side i intend to put high impendance milivoltmeter with 2 outputs; one for VU scale and other for scope....Not ready yet, still collecting infos...

[ivconic]

Hi
Again some theoric observation : It seem logical that coils shields MUST be isolated where they overlap,or else we are building small loops inside the coil , but i dont see anybody mentioning this.Is everyone isolating his shields?

regards,
Fred.

True! But Max and i think Qiuaozhi noted that few times on previous pages....

[Qiaozhi]

I do not agree there. We have different points of view. I already explained that i plan using my coils on quite different machines...I want my coils to be as much versatile as possible. I do not want to "tie up" specific coil to specific detector. Just look Fisher,Garret,Whites,Minelab....you are not pushed to buy exact coil with exact machine. If they have 1000 Spider coils available at shop, you can choose any of them to use with you...let's say CZ5, for example....
I simply refuse to beleive taht they nulled every coil with every machine in producing process..!? White's also; i tested some old coils with brand new machines - working perfect!? How come?
About tuning capacitors; yes, here i agree. You can achieve better performances if coil is fine retuned with it. But this you can do after basic nulling, on some specific machine...
Regards!

I understand what you're saying.
In the case of Fisher, Garrett, Whites, Minelab, however, they undoubtedly have a test setup in their individual factories for nulling coils, so (of course) all the coils they make for their machines will be the same, within certain manufacturing tolerances. Then when they design a new detector, it is designed to use the same coils. This just makes good economic sense. Then by default you can take an old Fisher coil and use it on a CZ5. Why not?

[Fred]

Hi
Again some theoric observation : It seem logical that coils shields MUST be isolated where they overlap,or else we are building small loops inside the coil , but i dont see anybody mentioning this.Is everyone isolating his shields?

regards,
Fred.

[Max]

little osc simulations

Hi,
I've downloaded LTspice and using some parts of files from porkluvr I'm doing some training on the simulator... just to see how to move around menus.

I'm happy of results cause I find it really intuitive and easy to use...but that's my impression... you could contestate!

Anyway, I've simulated the original (about) TGS osc with a 4.7 zener diode and 8V supply....

then I've changed the params... using a 15v zener diode (BXZ84C15L) to see the jump at output voltage.

As you can see with that +18v supply and 15v zener it gives about 30Vpp instead of original about 10Vpp: 3 times.

No other mods seem required e.g. for PN2222 that drives the 4024... but , of course, one have to put a stable +18v supply for osc section only (few mA current required)...even 2x9volts batteries could be good for tests.

So maybe people that want experiment with osc signal amplitude can do that way... well signal is not a perfect sinus on sim but I think could be ok for some raw tests.

I think that there's no need of that change on TGS... cause I found really good as is... but if someone would like to try... and inform us of results e.g. in air will be cool!

I can't do cause I have to dismantle the thing from housing and it's now hard work.

Best regards,
Max

[Max]

Hi Ivconic.
I agree with you but.....
I understand that there is big difference between air and ground.If one detector locate a coin on the air at 40 cm it will detect it at 20... 30 in the ground. But if detect a coin at 20 cm in the air it can't detect it at 25 cm in the ground. This is the point that i say that SS60 is winner. If i will detect with TGS a 25mm coin (2euro) at 30++cm at the air then i will compare it with SS60.
The problem with my TGS is that i can't locate a coin at the distance that you say that you detect. Maybe when i fine tune the Rx coil to detect it at same or near distance. I use a 32cm DDcoil so i must detect it at 30++cm.
Btw do you use an extra capacitor at the Rx coil? (15nf on the board and other cap on the coil)
Regards

Hi Geo,
I've tested my TGS with DD22 and works fine... but not as fine as with bandidoII I've made. I think I've optimized too much DD22 to work on bandidoII at 10Khz to have same depth with TGS.

Also with an OO coil that is very good on BandidoII I get good but not that good results on TGS: it's all about resonance and optimization.

So I've made Ivconic's coils (and other experiments with e.g. OO coils) and found it very good about depth... you need a coil tailored for it... and of course, audio is weak without mod but it's stable and you can ear coin signal at very good depth in air and then in ground too.

Don't use another previous coil with it if wanna see best results. Make using Ivconic's specs and you will see much more depth. Data are really accurate:

TX 100 turns
RX 105 turns
wire = 30AWG (0.25 without varnish)

Look at the picture I've posted some pages ago... look at drawing for nails/wood former and make the same.

Get right inductances and you will be fine with it and TGS... you have to optimize alignment using scope or just watching at detector sensitivity increase.

Best regards,
Max

[Max]

Ok the GoldenSabre works. I rotate the MPSA13 180degrees and now it is ok. I connected it only in manual mode but i dont like it. I null exactly the coil (with the scope at the out of LF353) but i did not connected any capacitor to the RX coil for fine tuning (there is only one capacitor 15nF on the board).
Results:
Audio........ very low.... it needs a audio amplified (LM380... 386). As i see with the scope there is change in the signal that speeker don't sound, so we loose depth.
Sensitivity........ medium.... 2euro coin at 25 cm , 50Euro cents 25 cm, 2cents at 18cm, aold greek coin 30mm at 28...30 cm.
MAybe today or tomorrow i will try to fine tune the coil and to see the max semsitivity of this detector. If the sensitivity is near at my yesterday test then Ankerr SS-60 is Big Winner.
Max can you tell me at what distance you can detect a 2Euro coin???
Regards

Hi Geo,
I use more often the 1eur coin in tests: I detect it at 35cm loud
If remember well 2 eur coin at more maybe 37cm... I will test again and report here.

That depth are only given by big coils in air... I mean not 8'' and the like but the Ivconic's 255x137mm or other in the 10'' range coils.

You need to null the coil for minimum voltage and on mine I get with a bit of patience something around 5mVpp. I cannot reach at now less than these voltages cause coil is big and overlaps are about critical.

You also need all the rest... I mean coil must be fixed very well in epoxy cause any movement will degradate your SNR cause of the integrations... and so average of signal.

On the ground the behaviour is good if you perform tests on medium soil and tune good way the GEB trimmer (use ferrite but don't null totally... just to ear small "cracks"... then test silver response after that).

Best regards,
Max

[ivconic]

No. I am using original setup as on schematic posted earlier.
My coil is 27cm (255x137) as described earlier..
To gain more depth you should null coil proper, as described earlier...
With 32cm coil i think you should detect 2cm coin at at least 40cm in the air and for sure at 25cm in the ground...maybe few cm more, depends of soil mineralization - most important!
For 32cm coil use 0.3mm wire, and approx. 92-95 turns for TX and 95-100 turns for RX, inductances; 6mH for TX and 6.5mH for Rx....
Disc.pot to "2", Sense pot. to "8", in Disc mode of course....
If you add 1M resistor you'll have much better audio response but also risk to ocassional chatters appear...again mostly depend of soil type...
Pleas when finished, DO some ground tests with both machines and post results here!
Regards!

[Geo]

Hi Ivconic.
I agree with you but.....
I understand that there is big difference between air and ground.If one detector locate a coin on the air at 40 cm it will detect it at 20... 30 in the ground. But if detect a coin at 20 cm in the air it can't detect it at 25 cm in the ground. This is the point that i say that SS60 is winner. If i will detect with TGS a 25mm coin (2euro) at 30++cm at the air then i will compare it with SS60.
The problem with my TGS is that i can't locate a coin at the distance that you say that you detect. Maybe when i fine tune the Rx coil to detect it at same or near distance. I use a 32cm DDcoil so i must detect it at 30++cm.
Btw do you use an extra capacitor at the Rx coil? (15nf on the board and other cap on the coil)
Regards

[ivconic]

I forgot to mention one fact; coil came with 1266, small spide 8", when tested with CZ5 is working perfect. Coil came with CZ5, 27cm Spider is working perfect with 1266...? How come?
I do have many other examples...dont want to bug much.
We missing the point here. My point is to null coil with less residual voltage possible on BASIC frequency. In TGS case freq. is 14kHz. So later i will have less error if that coil is used with Bandido, 10kHz...for example. Or i can decide to rise frequency to 12kHz...even less error. I dont need to null it using front end signal? Why should i do that?
I am standing to this point. Dont think further debate is needed on this. Everyone of use should use own method, which find the best for him. It is like debating on women!
To individual...no need to debate on this...
Regards!

[ivconic]

For this exercise, the noise generated in the preamp should not be a problem. Don't forget that this is really the signal that you're sampling, not the one from the coil. If you have noise issues here, then there's a real problem. Also remember that the coil will only be properly balanced for the frequency it was designed for. The only way you can keep your coils consistent between detectors is to put the tuning capacitors in the coil, not on the PCB.

I do not agree there. We have different points of view. I already explained that i plan using my coils on quite different machines...I want my coils to be as much versatile as possible. I do not want to "tie up" specific coil to specific detector. Just look Fisher,Garret,Whites,Minelab....you are not pushed to buy exact coil with exact machine. If they have 1000 Spider coils available at shop, you can choose any of them to use with you...let's say CZ5, for example....
I simply refuse to beleive taht they nulled every coil with every machine in producing process..!? White's also; i tested some old coils with brand new machines - working perfect!? How come?
About tuning capacitors; yes, here i agree. You can achieve better performances if coil is fine retuned with it. But this you can do after basic nulling, on some specific machine...
Regards!

[ivconic]

Ok the GoldenSabre works. I rotate the MPSA13 180degrees and now it is ok. I connected it only in manual mode but i dont like it. I null exactly the coil (with the scope at the out of LF353) but i did not connected any capacitor to the RX coil for fine tuning (there is only one capacitor 15nF on the board).

Results:
Audio........ very low.... it needs a audio amplified (LM380... 386). As i see with the scope there is change in the signal that speeker don't sound, so we loose depth.
Sensitivity........ medium.... 2euro coin at 25 cm , 50Euro cents 25 cm, 2cents at 18cm, aold greek coin 30mm at 28...30 cm.
MAybe today or tomorrow i will try to fine tune the coil and to see the max semsitivity of this detector. If the sensitivity is near at my yesterday test then Ankerr SS-60 is Big Winner.
Max can you tell me at what distance you can detect a 2Euro coin???
Regards

Geo, now add 1M resistor, if you want better audio response...
About performances;
you are anticipating too soon! Dont be so sure about Anker efficiency over TGS UNTIL YOU TOOK BOTH OUTDOOR and see real behavior on the ground. I am sure Anker doesnt stand any chance on the ground, comparing TGS. But, i dont need to tell you this, you will see yourself.

So i'll repeat once again, but for sure last time, not for you but for those unawared yet;
Tests performed in the air are not reference. Not accurrate. Detecting single coin in the air, on 40-50cm distance, DOESNT MEAN A THING!
Real detection is when coin is burried in the ground, COVERED WITH SOIL!
As real time prospector, i had chance to fully tested over 50 different detectors, on the ground, under REAL conditions. I am free to form opinion on that. Detectors like Anker, with output boosted that much, are absolutelly UNUSEABLE on some type of soils - most of types actually. You can easilly detect coin at 50 cm in the air. But in the ground it can NOT see same coin, even on 1/3 of air distance. TGS on the other hand is pretty optimized design with simillar air/ground performances (that's why is my favorite)....So distance you see in the air is more likely to be seen in the ground also, dependes mostly of quality you gained making it.
Dont guess me wrong, i have nothing against Anker....but last week i had chance to see on of those, tested, compared.....and when adjusted to work calm on the ground....it is very poor on performances, much,much under TGS...
Wish you luck!