TESORO GOLDEN SABRE

[ivconic]

Oh, another idea - walkman with extracted head (on longer cable) can be used to hear em field in speaker, also...

[Max]

Yes, it started as trial coil and turned to very serious ideas to adopt this as main type of coil for TGSL....
I didnt expected such good results at all!?
Most important fact is that this omega coil is indeed stabile as a rock.
I will repeat, it is very hard to balance it. Much harder than usuall dd coils.
But once it is nulled, well...well...
It think it will beat DD coil in depth also.
Not to mention narrowed area of detection.Pinpointing is 100% accurate with it. Actually area of detection is exact area covered by RX coil, no more, no less. In the past i made 2-3 omega coils for that md 3007, which was nomotion metal detector, poor performances comparing to TGSL. I didnt payed much of attention on those omega coils at the time. Those were made just to test detector, since original coil came with it was omega coil. I made few copies of md 3007 and logically made also coils for those by copying original coil. So i burried in my mind those as not so serious coils.
Now, i am equiped with more experience and payed a lot of attention on balancing and remaining exact inductances needed by TGSL.
I think i will propbably switch to this kind of coils in future. Yes next would be larger omega coil, at least 25-27cm. Huh, it will need further calculations and experiments to find exact number of turns for coils.
This time 0.25mm wire is used. On larger coil i guess 0.3mm would be more suitable to be used.
We will see...

Hi Ivconic,
thanks for the good news about it! I'd like to build one too.... larger version say from 25 to 27cm outer diameter.

I think you'll get really good results with larger one than 21cm trial coil.

Yes... the pinpointing ability of these coils is really cool feature, also if you lose about widescan action on these. I like this kind of coil cause I see it easy to shield and play about nulling... even more than DD.

Sure, critical nulling is always hard to get in few time... but I think this model is really easy compared to e.g. concentric-coplanar... where you have to cut wires... make lose loops and other dirty tricks to get them work with right null.

I'm awaiting for some wire too (0.25mm/30AWG) to build some new coil and think I will play too with omega in next weeks. I'm doing other stuff (digital) now and it's just an idea at the moment... but in future I'd like having one omega too for my TGS. I see it well on it.

I've also to check again TGSL circuit (I've buried it under some pile of other circuits) and start again with testing when got more spare time.

Anyway, thanks again for your efforts and goodwill in this stuff... I really appreciate much informations you provide.

Best regards,
Max

[Max]

Hi Ivconic,Now,I null the coil at 17mv VPP,the sense is good.
but I have another question,please help me.
Just like you had said i use two separate coaxials cable. the question is
if i tuch the cable,or bend the cable,the machine will beep.it make me crazy.

Regards and thanks for your support.
Here is my coil and cable.[ATTACH][ATTACH][ATTACH]4517[/ATTACH][/ATTACH][/ATTACH]

Hi,
I think you have to fix cables to pole using some tape or other stuff plastic made better.

If you leave cables free to move you'll become crazy about false signals.

Also use good quality wires/cables (e.g. some computer cables are good for this) with low capacitance... cause you don't want too extra capacitance added to the oscillator / rx sections... also some audio stuff is good for this.

Remember... we are using extremely hi amplification chain in TGS so... any small change due to movements etc will make it sound: make device totally solid/rigid stuff.

Kind regards,
Max

[zzy]

Thanks

Hi Ivconic and Max,
Very thankful for your help,I found the reason: I'am too stupid ,I forgot connect the RX to gnd,Now the coil null at 8mv VPP.but the sense is no increase.the machine will not beep if i touch the cable. I fix cables to pole using some tape,it's very good.
Thanks for Ivconic and Max support!
Now I detect 10eur-cents from 23cm in all metal, on air.But on notch mod it's only detect a gold ring at 11cm.

[WM6]

Instead telescope antenna on Zahori, i put small 2cm coil taken from old 5.25" floppy (step motor in in has several coil segments - small and cute for this job)...

Very fancy idea, ivconic, you are boss, you are Mr. O'Coil!!!

One can measure this by an old long known versatile amateur radio instrument, so called grid dip meter (or dip meter, or GDO). Very simple to build, one fet (or planar one, even vacuum tube) transistor, variable C, pot and small coil as you taken from step motor. There are enough schematic to find on WWW. For MD purposes inductivity of used coil have to be in limits of common L of MD coils.

Here some history and ideas to build GDO:
http://www.noding.com/la8ak/m11.htm

There are Q-meter and other construction ideas too.

It is interesting to measure changing of EM field around coil putted on soil not only in air.

[ivconic]

"..It is interesting to measure changing of EM field around coil putted on soil not only in air..."

This is crucial! Once for all,finally to establish losts at soil surface. Losts or attenutaion - call it anyway you want.

[zzy]

test

Hi Ivconic and Max,
How to test the TGS sense?
I move up and down,it seems got more deeps,
and i make the coin upright.it got more deeps too.
this picture is my test result:


how do you test the machine?

Kind regards.

[WM6]

Hi Ivconic and Max,
How to test the TGS sense?
I move up and down,it seems got more deeps,
and i make the coin upright.it got more deeps too.
this picture is my test result:
[ATTACH]4521[/ATTACH]
how do you test the machine?
Kind regards.

Good observations zzy. Results of measurement depends on geometry of targets position in soil and the way of coil motion too. The same in the air test. It depend on how thick lines of EM force decline to main target (e.g. coin) surface. On principle movement of test coin in air imitate coil movement against soil surface, mean that have to be parallel to coils down side surface. But fundamentally every measurement is correct by self and at the same time not correct in comparison to other measurement, when, because of different applied propagation, is not comparable. So, on measurement is very important to give participant all measurement procedure data to overcome subjectivity and to assure that results are comparable (if this is important of course - if not, measurement speaking for itself).

[WM6]

[quote/]I move up and down,it seems got more deeps,
and i make the coin upright.it got more deeps too.
.[/quote]

[Max]

Hi Ivconic and Max,
How to test the TGS sense?
I move up and down,it seems got more deeps,
and i make the coin upright.it got more deeps too.
this picture is my test result:
[ATTACH]4521[/ATTACH]

how do you test the machine?

Kind regards.

Hi zzy,
I test like at left side: coin flat vs coil, move left to right or right to left , so orthogonal to normal axis of coil and parallel to windings.
I test at each cm if sound or not... then refine to get maximum indication with resolution of 1/2 cm.

I use also second method (right side) moving front/back larger objects like coke cans or similar e.g. iron or copper plates.

The first method is much like you do when search on soil... sweeping left to right and reverse. The second method is good to understand if device as some inertia or similar... or, in other words, if it's fast or not.

The first method is good for small stuff , like coins... cause you can evaluate also the spatial sensitive area in front of coil... like described too in Tesoro's manuals for detectors similar... (bandidoII).

The second method is good to test with ferrite too... I use it much for little tests with rods to see how much detector is influenced by "height" variations in "magnetized soil" (emulated by ferrite rod effect).

Sure... for depth measures the first, leftmost, method is the one you have to use I think.

Kind regards,
Max

[Max]

[quote/]I move up and down,it seems got more deeps,
and i make the coin upright.it got more deeps too.
.

[/quote]

Hi,
lines described are not like in real coils: fluxlines have maximum coupling with target when it's flat (like on the left of picture) and minimum when it's tilted 90°, so with sharp edge on normal axis.

The maximum the surface orthogonal to normal axis and the maximum the flux chained at reasonable distance from coil.

You can notice it very easy... just try sweeping a 3cm coin flat and then tilted nearing till detector beeps in both cases: when flat you'll reach maximum performance, so depth on air; when tilted like on the right you'll get minimum effect at far distance (cause flux lines intercept just minimum area on conductive target so current paths are minimum size too, and currents very low).

On soil... stuff is different cause also a tilted target could give good signal if e.g. developed (like iron) some "halo" (salts and compounds all around soil matrix near metal). But this happens just spot and not always.

Kind regards,
Max

[ivconic]

I test like at left side: coin flat vs coil, move left to right or right to left , so orthogonal to normal axis of coil and parallel to windings.
Same as me..

[WM6]

Hi, lines described are not like in real coils: fluxlines have maximum coupling with target when it's flat (like on the left of picture) and minimum when it's tilted 90°, so with sharp edge on normal axis.
The maximum the surface orthogonal to normal axis and the maximum the flux chained at reasonable distance from coil.
Kind regards,
Max

Agree Max. Thank you for explanation.
Maybe this reflect in some better way reality:



One more question:

Factory made coils are adequate adapted to MD circuit parameters, suppose at first by inductance L and resistance R of coil.

When we work out other shape of coils for same MD is hard to achieve both L and R of original coil (cause of wire diameter, other parasite C etc.).

Usually it is easy to reach one of original parameters whether L or R, but not both at the same time.

My question is: what is better to follow during other shape coil construction, original calculated inductance or original given resistance of coil? (If we cannot to achieve both at the same time of course.)

Thanks!

[ivconic]

Agree Max. Thank you for explanation.
Maybe this reflect in some better way reality:



One more question:

Factory made coils are adequate adapted to MD circuit parameters, suppose at first by inductance L and resistance R of coil.

When we work out other shape of coils for same MD is hard to achieve both L and R of original coil (cause of wire diameter, other parasite C etc.).

Usually it is easy to reach one of original parameters whether L or R, but not both at the same time.

My question is: what is better to follow during other shape coil construction, original calculated inductance or original given resistance of coil? (If we cannot to achieve both at the same time of course.)

Thanks!

I will take freedom to make some notes here, on this;
yes it is right question!
L is value included in formula to calculate oscilator frequency along with C, since most of oscilators here deal with LC coils.
So main parameter we must obey here is L for sure.
R is also important. Unproper load could easilly distort RX opamp and lead it to saturation or...make inputs "deaf" and choke induced current. So obviously R should reamain in some limits, i would say; approximative to original resistances. On TX side also unproper load could easilly saturate transistor and produce lot of harmonics, and vice versa, easilly choke it and stop oscillations or cut amplitude to unuseable values. Also current drain rises significantly.I spotted elegant solution at Garrett Scorcher coil where serial resistor is used in manner to prevent unexpected variations in amplitude, mostly, along with other function there.
At TGS we have 2 x 5K1 resistors having limiting role there. I experimented with those values and discovered that down to 3K3 amplitude and induced current remain unchanged. Although it would be better to strictly use metal film resistors there with high Q, since some low quality resistors do affect amplitude at opamp inputs.
So when making coils i usually do respect L strictly to exact value and R approximately with 10% jitters...
Recently i spotted another elegant solution at RX front end. At Fisher 1265 LT1007 is used with adjustable gain...very nice solution.Also could give some ideas and lead to more experiments...sheeesh! Neverending story!!!

[zzy]

So strange

Hi,Max

I sweeping a 3cm coin flat and then tilted nearing till detector beeps in both cases

My test result is strange.
i use DD coil.
when flat, I reach 25cm,
when tilted, I reach 27cm,
my test shows that
so i think WM6 is right.when tilted,the machine gets more deepth.
fluxlines have maximum coupling with target when it's tilted 90°.