TESORO GOLDEN SABRE

[Fred]

Tiktak,
Also i think you mentionned before that you did not clean your PCB.
You MUST, also you must be sure you used a non-acidic solder flux,if you used some, or else you will have to make a new PCB...

regards,
Fred.

[Molzar]

At last I've found some time to test the overlapping coil configuration that most of you are using to build your homemade coils. The Tesoro factory-made concentric coils are all constructed to provide an initial phase-shift between the TX and RX of about 120 degrees, with the RX signal measured at the output of the RX preamp. All targets give a phase-shift to the left, with ferrous targets causing a decrease in amplitude, and non-ferrous causing an increase.

I constructed a simple test using two round coils of 180mm diameter. The TX coil consisted of 115 turns of 0.56mm enameled wire (5.6mH) and the RX had 122 turns (6.5mH). I was really trying for 5.9mH on the TX, but this discrepancy will not affect the test.

To get the correct 120 degree phase-shift between TX and RX, it is necessary to gradually move the two coils together until you reach a null point, and then go through the null until you have a few mV at the RX input. You can find the null point more easily by monitoring the preamp output with a scope. In this position, ferrous objects will cause a decrease in amplitude, and non-ferrous will cause an increase. However, all metallic objects will cause a phase-shift to the right. This is, of course, different to the concentric coils, but because of the way this type of analogue detector works, the direction of phase-shift is not a problem.

After some experimentation with this test setup, it is clear why Tesoro deliver their detectors with concentric coils. Has anyone tried constructing an omega coil for the TGS? I would think that the omega would be much easier to set up than the concentric, and may perform better than the DD.

Hi Qiaozhi,

So with DD or OO coil configuration shift is to the right. Didn't Max get shift to left? or was he using concentric coil?

Interested in why "direction of phase shift is not a problem" on TGS. Can you please explain? Why do you think Tesoro deliver concentic coils, why is better?

Molzar

[Molzar]

Cable

Nelson,

I use Belden 8723. This is foil sheilded (2) twisted pair, very nice!

Also you could used (2) RG174U (thin) coax cables. (like for scope probe)

You could even use (for bench testing) (2) regular coax (RG6, RG58 or 59).


Molzar

[Qiaozhi]

Hi Qiaozhi,

So with DD or OO coil configuration shift is to the right. Didn't Max get shift to left? or was he using concentric coil?

Interested in why "direction of phase shift is not a problem" on TGS. Can you please explain? Why do you think Tesoro deliver concentic coils, why is better?

Molzar

I think Max said that he could confirm there was a phase-shift to the left with a Tesoro factory-made concentric coil, but do not remember what he found with the DD.

Actually, the difference in phase-shift direction will produce different results. For the concentric coil, a left-phase shift means that the target is detected as it enters the RX coil, whereas a right phase-shift will only detect the target as it leaves the RX coil, which makes it more difficult to pinpoint amongst the trash. For a DD coil, the effective detection area is a thin strip in the middle of the coil that runs from front to back. In this case there would be little difference between a phase-shift in either direction, due to the narrowness of the detecting area.

Regarding whether a concentric or DD coil is the best, is often a matter of preference. You have to overlap consecutive sweeps with a concentric, which means that the area cannot be covered so quickly. But they do have superior pinpoint capabilitie,s and are better at picking out targets in trashy or iron-infested areas. DD coils have a wider sweep area, and there is no need to overlap sweeps, and are also less affected by ground mineralization. I believe that Tesoro ship their detectors with concentric coils because these give the best overall performance for the greatest number of customers.

[scevlik]

Hi!

I have redy the next coil DD255x137.Results are very good 35-40cm with 3cm coin.Disc. also work correctly.Still i heve next problem,when the coil is puted on the desk work good.But when I bring him from desk detector start self oscilating,and only can hear beeb.It is same if i stroke to the desk.

[nelson]

How i can measure RX frequency, to know if RX coil is resonating at 16.XXX Khz?
Regards
Nelson

Hi Qiaozhi,

I've read many posts on Tx frequency of ~14.6 KHz here, but where does the Rx frequency (16.12 KHz) you stated above come from?

Will try swapping coils tonight...

Thanks,

Molzar

[Max]

Hi!

I have redy the next coil DD255x137.Results are very good 35-40cm with 3cm coin.Disc. also work correctly.Still i heve next problem,when the coil is puted on the desk work good.But when I bring him from desk detector start self oscilating,and only can hear beeb.It is same if i stroke to the desk.

Hi,
ok...I suppose you didn't fix it already so you need to epoxy it... of fix in another way but very tight and avoiding any movement relative tx/rx . Any vibration would change coupling between tx and rx and so you get false signals when move the coil.

We discussed fixing with epoxy somewhere before : you need liquid epoxy stuff to do perfect way. Can use also other stuff but I suggest epoxy expecially clear one used for surfboards: I found it extremely good for coils.

Kind regards,
Max

[Max]

I think Max said that he could confirm there was a phase-shift to the left with a Tesoro factory-made concentric coil, but do not remember what he found with the DD.

Actually, the difference in phase-shift direction will produce different results. For the concentric coil, a left-phase shift means that the target is detected as it enters the RX coil, whereas a right phase-shift will only detect the target as it leaves the RX coil, which makes it more difficult to pinpoint amongst the trash. For a DD coil, the effective detection area is a thin strip in the middle of the coil that runs from front to back. In this case there would be little difference between a phase-shift in either direction, due to the narrowness of the detecting area.

Regarding whether a concentric or DD coil is the best, is often a matter of preference. You have to overlap consecutive sweeps with a concentric, which means that the area cannot be covered so quickly. But they do have superior pinpoint capabilitie,s and are better at picking out targets in trashy or iron-infested areas. DD coils have a wider sweep area, and there is no need to overlap sweeps, and are also less affected by ground mineralization. I believe that Tesoro ship their detectors with concentric coils because these give the best overall performance for the greatest number of customers.

Hi,
yes my original 9x8'' shift to the left; I suppose all concentric by tesoro are this way, like you stated... but have just the 9x8'' original and didn't test others for phase till now.

I remember also that all my DD shift one way... but now I don't remeber now if left or right ...must check again in some spare time (if I find some I mean... very busy these days).

Kind regards,
Max

[Aziz]

Hi,

I observed on DD coils phase anomalies on metal pins (like drills). The phase shift is dependend on target shape, orientation and on placed coil position.
Please, check this out.
Aziz

[amtech2005]

TESORO GOLDEN SABRE

WONDER HOW GARRETT'S TARGET IMAGING WORKS . HIGH POWER DSP ?? ANYWAY SPEAKING OF COIL POSITION !!! WHY DOES A TWO-BOX HAVE THE REAR COIL OUT OF PHASE WITH THE FRONT COIL ???? AZIZ , MAYBE YOU NEED TO DESIGN A MULTI-PHASE SEARCH COIL FOR STANDARD DETECTORS. THIS SHOULD BE ON OUR DESIGN GROUP THREAD NOT HERE ... HAVE A GOOD DAY !! ...................EUGENE

[Qiaozhi]

How i can measure RX frequency, to know if RX coil is resonating at 16.XXX Khz?
Regards
Nelson

I guess you missed my previous reply to this question:
http://thunting.com/geotech/forums/s...postcount=2273

[erolunall]

Hello

One friend said adding 2.2k paralel to 2.2k R increasing deepth 5 cm

This 2.2k At right bottom side of pcb connected 2n2907

he wrote he found 2 cm coin at 60 cm undreground.

with tgs and ivconics coil 257mm 140mm. DD .

regards
Erol

[Max]

WONDER HOW GARRETT'S TARGET IMAGING WORKS . HIGH POWER DSP ?? ANYWAY SPEAKING OF COIL POSITION !!! WHY DOES A TWO-BOX HAVE THE REAR COIL OUT OF PHASE WITH THE FRONT COIL ???? AZIZ , MAYBE YOU NEED TO DESIGN A MULTI-PHASE SEARCH COIL FOR STANDARD DETECTORS. THIS SHOULD BE ON OUR DESIGN GROUP THREAD NOT HERE ... HAVE A GOOD DAY !! ...................EUGENE

Hi,
don't know of target imaging stuff... but the coils in 2box are 90° out cause this way there's minimal (ideally zero) magnetic coupling between them... so rx receive "zero" signal in absence of target.

Kind regards,
Max

[Max]

Hello

One friend said adding 2.2k paralel to 2.2k R increasing deepth 5 cm

This 2.2k At right bottom side of pcb connected 2n2907

he wrote he found 2 cm coin at 60 cm undreground.

with tgs and ivconics coil 257mm 140mm. DD .

regards
Erol

Hi,
2cm diameter at 60cm ? Impossible... so I think if he found it maybe there's something else in soil (at fewer depth) he maybe miss during excavation and then when he bring detector again it detected the coin there (say after 30-40 cm already dug... in the hole digging more deep).

This is a possible scenario... happened to me with some small targets cause I found some copper scraps (small) were dispersed in the ground just 30cm above the "good" stuff...

In one of this excavation I removed for 30cm depth about 60cm diameter large hole... without finding anything at first (2 small copper scraps I found just later with lot of efforts there) but clearly pinpointing 4 good targets (silver) in the bottom of the hole just easy. SO EFFORTS WERE GOOD SPENT THAT TIME!

Kind regards,
Max

[Unregistered]

Hi, in post #2180 I had stability problems with GS, now they are solved and GS works well and is very stable. Maybe some of my experience will help someone with similar problems.
1. coil. It has to be absolute solid, use some form and lot of epoxide glue, if you swing coil and it hits grass or something and bends a bit, it will give lots of false signals.
2. Battery. In my case problem was a battery, I use 10 AA chargeable cells, two of them were bad and with 9,... volts my GS dont work. Fully charged with 13 volts all metals and disc both
work well, if accu drops under 12v it goes unstable in all metal, and under 10 also in disc mode.
3. wiring. My GS worked much stable after I used inside a case for RX and TX shielded leads and banded all other wiring together.
4. audio. I never had a problem with weak audio, but i also use as a Max 16ohm 8cm speaker from old mac computer.