TESORO GOLDEN SABRE

[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]

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...

[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,
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...

[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]

225km...

[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.....

[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=

[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.

[ivconic]

Heil Quiaozhi!
I'll do that! Thanks!

[ivconic]

Come to think...! Simillar should be done in Disc mode on other channel? Is'nt it? Or not...due relative position of Disc pot..?
Stupid me! Of course not! But another thing; low down Disc to minimum,measure second channel;
a) if not zero, than add or substract some resistance on one side of pot. to gain zero,
b) if zero, increase a bit and measure again;

Why? Try to achieve linearity in Disc range, cose i noticed some non-linear behavior also, there..
At the moment, if Disc pot. is lower than "2" than producing chatters more often, if Disc. pot is higher than "3" than no chatters at all...
That's why i suspected this stage, at first place...
I do beleive there are some differences in FET behavior also. I put J107, not BF245 or other.. ?
I think we are pretty close to solve this problem....
Thank you again Quiaozhi, your suggestion gave me some other ideas...
Best regards!

[Qiaozhi]

Come to think...! Simillar should be done in Disc mode on other channel? Is'nt it? Or not...due relative position of Disc pot..?
Stupid me! Of course not! But another thing; low down Disc to minimum,measure second channel;
a) if not zero, than add or substract some resistance on one side of pot. to gain zero,
b) if zero, increase a bit and measure again;

Why? Try to achieve linearity in Disc range, cose i noticed some non-linear behavior also, there..
At the moment, if Disc pot. is lower than "2" than producing chatters more often, if Disc. pot is higher than "3" than no chatters at all...
That's why i suspected this stage, at first place...
I do beleive there are some differences in FET behavior also. I put J107, not BF245 or other.. ?
I think we are pretty close to solve this problem....
Thank you again Quiaozhi, your suggestion gave me some other ideas...
Best regards!

Also easy to do...
To get the correct minimum position for DISC, monitor the output of Q6 (above Q7) and adjust DISC control to get maximum voltage. This should then reject ferrous targets but allow all higher conductivity targets, such as foil, pull tabs, coins, etc.

[ivconic]

Yes....and later add or substract some resistances on pot pins to achive full linearity....

[ivconic]

Actually i only reversed it!? Never mind....i'll do that later....Time to "sharpen" TGSL a bit more....
LOL

[Geo]

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

Thanks Qoaozhi