TESORO GOLDEN SABRE

[Qiaozhi]

Quite right! I noticed also when GEB adjusted to totally "blank" ferrite rod than device not performs quite well on the field, but when adjusted to rarely "crack" on ferrite - than performs excelllent on the field.
But how can i monitor exact zero-crossing there? Still not clear many things to me! What points should i monitor on scope? I tried some things but without knowing exactly what am i doing!!??? Heh,heh,heh....

Actually, this is very simple to measure. See attached image.
Switch to All Metal mode, and connect scope to point marked GEB. Then adjust GEB control until you have 0V DC. This should also work with a meter instead of the scope.

[Qiaozhi]

Do you have Route66 Europe? Or Microsoft Autoroute?

Also, try here -> http://maps.google.co.uk/maps?oe=UTF-8&hl=en&tab=wl&q=

[ivconic]

There is bus line Belgrade-Sokobanja twice daily....I am not sure about termin...If you come with car than it is 2 hours of driving in one direction.Also if you come with ca than you must pass highway, 30km away from Sokobanja...
Do you have Route66 Europe? Or Microsoft Autoroute? Easiest way to image this. I can send you plan with directions if you want?
But if you come with plane than you'll go directly to BG...
What was with your Anker?
Can you perform some fast air tests with few items? Coin 1cm, coin 2cm, Cola can.....

[ivconic]

225km...

[Geo]

Look at this one Geo:

http://www.soko-banja.org/

Regards!

Hi Ivica. I think that it is long Distance. The fights are at the Beograd. If i don't make mistake Beograd is about 200Km from your city. I will come on 2 November for 2 days with my son. Tell me about the exactly distance
Regards

[ivconic]

Hi,
only way, I think, is to watch it on the scope... one probe to the fet gate of its channel (geb) signal and another to the RX signal.

If you haven't scope ready to test it...I'm sure that also a sound blaster or similar can give you a scope drawing of what happens using some freeware program.

I noticed also that total ferrite ignoring is not always good: when searching in hi-infested sites maybe it's safe doing that present... but for normal soil this will overbalance gnd thus giving actually an out of balance... no good.

That's why I suggested people setting it on medium soil directly by notice the detectior behaviour... much like one do with bandidoII and similar with external geb pot.

I noticed also another thing: when perfectly balanced the sound I get from distant targets are really weak without the audio mod. So I use headphones to be sure I ear the signal.

At that setting it reacts to ferrite toroids with small cracks at overlaps and central zone of DD... and never at borders... that happens at 0mm to 15mm from bottom of coil... never at e.g. 5cm or more.

That way I get exactly same depths I get at an arbitrary geb setting on air... but have to take much more care on audio: is weak. When test at workbench I use speaker but outside never do that... think I could also throw away the speaker from it without pain cause of that!

Best regards,
Max

Agree.That's why put tha 1M resistor as KT315 suggested.Much better audio response. But than bleeping occured!? Somehow i am wandering in the circle!? I do have oscilloscope, but better if i dont! It is old, obsolete,one channel and without internal synchro...!? Very,very old....Must buy new one asap!
BTW your story justify another thing; Relic Hawk is probably the best VLF ever....yet without speaker! Only earphones available with it...

[Max]

Quite right! I noticed also when GEB adjusted to totally "blank" ferrite rod than device not performs quite well on the field, but when adjusted to rarely "crack" on ferrite - than performs excelllent on the field.
But how can i monitor exact zero-crossing there? Still not clear many things to me! What points should i monitor on scope? I tried some things but without knowing exactly what am i doing!!??? Heh,heh,heh....

Hi,
only way, I think, is to watch it on the scope... one probe to the fet gate of its channel (geb) signal and another to the RX signal.

If you haven't scope ready to test it...I'm sure that also a sound blaster or similar can give you a scope drawing of what happens using some freeware program.

I noticed also that total ferrite ignoring is not always good: when searching in hi-infested sites maybe it's safe doing that present... but for normal soil this will overbalance gnd thus giving actually an out of balance... no good.

That's why I suggested people setting it on medium soil directly by notice the detectior behaviour... much like one do with bandidoII and similar with external geb pot.

I noticed also another thing: when perfectly balanced the sound I get from distant targets are really weak without the audio mod. So I use headphones to be sure I ear the signal.

At that setting it reacts to ferrite toroids with small cracks at overlaps and central zone of DD... and never at borders... that happens at 0mm to 15mm from bottom of coil... never at e.g. 5cm or more.

That way I get exactly same depths I get at an arbitrary geb setting on air... but have to take much more care on audio: is weak. When test at workbench I use speaker but outside never do that... think I could also throw away the speaker from it without pain cause of that!

Best regards,
Max

[ivconic]

Hi All,

George Payne on fixed (preset) vs adjustable GB
and coil design.

http://jb-ms.com/Baron/gb.htm

A good read for any who have not seen it.

I agree! That's why i do respect him a lot....among other things...
Exactly that Quiaozhi talked about in latest post...

[ivconic]

The ground balance works by sampling the received signal at the zero-crossing point. The theory is that both ferrous and non-ferrous targets affect the amplitude and the phase of the received signal, whereas neutral soil will only cause a decrease in magnitude. There is no phase-shift. Since you are sampling at the zero-crossing, the GEB channel cannot detect a change in the amplitude of the signal unless there is also a phase-shift. Ferrite causes a similar response, and that's why it's often used to find the correct GEB setting. Unfortunately ferrite does not react exactly like real soil, and the offset can be as much as -5 degrees. If you're using a preset GEB, then you will need to adjust it off from the ideal position by a few degrees and set the threshold to silent search, but the best solution is to have an external GEB control. If you set the GEB control to any position other than sampling at the zero-crossing point, then it's not acting as a ground balance control.

Quite right! I noticed also when GEB adjusted to totally "blank" ferrite rod than device not performs quite well on the field, but when adjusted to rarely "crack" on ferrite - than performs excelllent on the field.
But how can i monitor exact zero-crossing there? Still not clear many things to me! What points should i monitor on scope? I tried some things but without knowing exactly what am i doing!!??? Heh,heh,heh....

[ivconic]

"..That's a secondary effect but could have its importance in whole MD performances... expecially for deep and small targets.

What do you think ?.."

Dont know yet.
Worth of trying. I'll try that and later inform here...Might be that some extra changes needed arround front end...i'll see.

more information

Hi All,

George Payne on fixed (preset) vs adjustable GB
and coil design.

http://jb-ms.com/Baron/gb.htm

A good read for any who have not seen it.

[Qiaozhi]

So, i tried to setup alternative "zero" with this way of nulling coil. Why? TGS already have sufficient GEB&DISC adjustments...
Dirung working with TGSL under real conditions i noticed situatin on SOME fields TGSL cant be grounded well; it still can produce fast chatters ocassionally...similar with almost all other detectors.Even GT (which is very stabile) sometimes can jitter a bit. Despite all my love for TGSL i still have to say that its GEB is not perfect. When testing in workshop it can absolutely reject ferrite,iron and simillar....even that famous mineralized clay. But outdoor i noticed some jitters from time to time. To repeat; when handling with cable i cant provoke any falses, also touching coil - still no falses, very calm and stabile. But swinging arround few inches over soil surface, sometimes it can bleep??? I still havent find out what should be the reason of that? Several different coils were checked, so i simply can not blame coils for that...Adjusting GEB trimmer slitely mm per mm wont solve problem.Actually GEB trimmer is more likely to affect discrimination than GEB? If rised more you can easilly lose some coloured metals like nickel coins or small silver...GEB trimmer is adjusted at the very point where is just about to lose nickel....
So i was thinking somehow to extend that part of scale. But how?
So i left device aside and tried with coil.That's why nulled latest coil in a bit more "positive" manner...Is it good? I dont know yet. I'll see when rain stops .
I want to ask you is there any other way to extend GEB adjustments on TGS?
Putting multi turn trimm wont solve the problem..

The ground balance works by sampling the received signal at the zero-crossing point. The theory is that both ferrous and non-ferrous targets affect the amplitude and the phase of the received signal, whereas neutral soil will only cause a decrease in magnitude. There is no phase-shift. Since you are sampling at the zero-crossing, the GEB channel cannot detect a change in the amplitude of the signal unless there is also a phase-shift. Ferrite causes a similar response, and that's why it's often used to find the correct GEB setting. Unfortunately ferrite does not react exactly like real soil, and the offset can be as much as -5 degrees. If you're using a preset GEB, then you will need to adjust it off from the ideal position by a few degrees and set the threshold to silent search, but the best solution is to have an external GEB control. If you set the GEB control to any position other than sampling at the zero-crossing point, then it's not acting as a ground balance control.

[Max]

Hi,
watching again it I start thinking at fact that LF353 diff config would amplify differential signal from the external leads ...so the sum of the two halves of RX... and that the effect respect GND is totally differential... so no noise or signal respect to GND at rx external leads...cause of the center tap.

An advantage could be related to shield to coil capacitive effects during transients... that configuration will null the effect due to the fact the shield will always see same voltage for the 2 rx external leads , also with huge differences respect to the real voltage potential between the two: this will improve SNR if transients generate falsing due to capacitive effect inside the housing... due e.g. to the previous config (one lead at GND and the other "floating") that seems a realistic perspective for an MD coil.

That means, if noise is related to e.g. capacitive histeresys of dielectric between coil and shield, we'll get a more stable design that way.

Ideally that will improve SNR but considering the splitting of RX in two sections we'll have to consider also the mutual inductance effects between the two-> we'll have an air core transformer at RX and that will add inertia to the RX side cause of magnetic mutual energy interactions of the two halves.

That's a secondary effect but could have its importance in whole MD performances... expecially for deep and small targets.

What do you think ?

Best regards,
Max

[Max]

So, i tried to setup alternative "zero" with this way of nulling coil. Why? TGS already have sufficient GEB&DISC adjustments...
Dirung working with TGSL under real conditions i noticed situatin on SOME fields TGSL cant be grounded well; it still can produce fast chatters ocassionally...similar with almost all other detectors.Even GT (which is very stabile) sometimes can jitter a bit. Despite all my love for TGSL i still have to say that its GEB is not perfect. When testing in workshop it can absolutely reject ferrite,iron and simillar....even that famous mineralized clay. But outdoor i noticed some jitters from time to time. To repeat; when handling with cable i cant provoke any falses, also touching coil - still no falses, very calm and stabile. But swinging arround few inches over soil surface, sometimes it can bleep??? I still havent find out what should be the reason of that? Several different coils were checked, so i simply can not blame coils for that...Adjusting GEB trimmer slitely mm per mm wont solve problem.Actually GEB trimmer is more likely to affect discrimination than GEB? If rised more you can easilly lose some coloured metals like nickel coins or small silver...GEB trimmer is adjusted at the very point where is just about to lose nickel....
So i was thinking somehow to extend that part of scale. But how?
So i left device aside and tried with coil.That's why nulled latest coil in a bit more "positive" manner...Is it good? I dont know yet. I'll see when rain stops .
I want to ask you is there any other way to extend GEB adjustments on TGS?
Putting multi turn trimm wont solve the problem..

Hi Ivconic,
as always you give us good informations and ideas about how to approach problems.
I've tested behaviour on 5 different soils at the moment and find that 2 gave me problems with fixed geb setup: the trimmer position I've adjusted on middle soil gave me bad working on 1 soil made of a mix of sand (or similar to sand) and clay... all right - iron salts and oxides are present there. Erratic bursts of noise when e.g. a small ammount of soil (not perfectly plain) give such an height gradient (like a small "hill") respect to the sorrounding part of soil.

In plain area the same effect occours at random... and I don't know cause but think there is something in the underground layers structure that point detector on the same way or hot rocks, result is the same: noise.

In another soil I get some rare bleeping similar: soil is made mainly of clay this time.

Other 3 test sites showed perfect performances and nice depths with NO BLEEPING AT ALL. Soils are different and made of mix of clay and "sand"...one has hi organic compounds presence on first 10-15cm.

Is that GEB that need adjusting ? I think so.

I've made bandidoII and it has an extended disc mode and multiturn GEB pot that make it possible find the exact spot where GEB is perfect (but not so easy to find). I think that TGS would benefit too of a multiturn GEB pot... but I agree also with you on DISC effect of geb trimmer (really easy to see): all right... multiturn pot won't solve our problem totally.

Center tap to GND ? I don't know if could solve it, but it's an idea... if noise, as seems, is related to ferromagnetic gradients probably their amplitude influence would be cancelled out by this config respect to GND...

I think that it's a forced diff. configuration for the two halves... thus giving cancel of signal due to noise... but also to targets... : that way will be more stable but I'm scared we'll lose some depth.

Only way to know is it could solve or reduce problem is try it.

Kind regards,
Max

[ivconic]

?

How about this substitution for RX coil?
Any benefits,drawbacks...?
What do you think?