TESORO GOLDEN SABRE

[tiktak]

Hi

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.

Shouldn't!? Try to adjust GEB trimmer a bit. RX is connected to gnd in coil but not on pcb. Both Al foils are connected togather as well as both cable shields - in coil, but separatelly at pcb, without RX on gnd (as told before).

Hello,
I cant understand this.Until now I have used 2 together shielded cabels wired the way showed on your picture.But now when I read this I see many changes!So how to wire?TX and RX stat points to 2 cores,shields of cables and faradey cages all together.But then where to conec the ends of RX and TX?And on other hand how to wire to PCB?Cores to upper points for TX and RX?And leave ground point for RX empty.And conect shields of cables to TX ground point only?
If you draw a new clear picture I will be very greatefull.
Thanks.

p.s.I went prospecting yesterday with my TGS and havent found a single coin,but many rubbish colored ithems and a few large Irons afcours.But I have noticed that when I go near a high voltage line,my detector is not working!~!When I pick up my coil I can hear the electricity passing buy!!!A little bit scary.....The problem is that this is a good spot and I cant took advantage of it.
This time I had a feeling that my detector is not penetraiting!!!The land were just prepared for seeding and there were hugh level differances!May be because of this were the poor performance?

[tiktak]

Hi

OK, i got first,preliminary results;
first i have to say, nulling omega coil turned to be much
more difficult than DD coil???!
(Last time i made omega coil was for MD3007 and i didnt used
present method by measuring induced voltage in RX coil)
It need 1/10mm to drop to 0 volts or to jump to 20-30mV!!!??
After much effort somehow i managed to achieve excellent null.
At 200mV range it says 0.01...more than good!
OK, than i resoldered RX wires from miliviltmeter to TGSL.
WOW! What a stabillity!!! I dont beleive my eyes!!!
It is very,very stabile coil!!!! Superb over DD coil!!!
Discrimination is P E R F E C T !!! Perfec,perfect!!!!
Ferrite rod is absolutelly invisible for this coil even if i
lower GEB trimer much "down" from usuall value, usually trimmed
with DD coil.... Usually, when DD coil nulled well, there are some
mum "cracks" on ferrite rod with trimmer on 60%. I usually left that
way and later turns detector acts pretty well on soil.
But now, with this coil - not "cracks" at all! Trimmer at half - no
"cracks". Thin silver coin - yes, detected loud and clear!
Wow.
Ok, depth is lower than 27cm coil. 1 Euro coin detects very easy at 24cm
in air. 1.5cm nickel coin at 28cm.
Considering diammeter of this omega coil - 21cm, i think it is not
shallow comparing 27cm DD coil, not at all.
Next thing i'll do is to make 27cm Omega coil and than see real differences.
Bit now, i left out of wire, so this will wait for week or more.
But discrimination is really perfect. Large iron claws - absolutelly invisible
in disc mode.
What to say more? Need to finish it and than perform full test outdoor on the
real field.
Until than...


Regards Max!

Hi,
I have looked again at your pictures and I noticed that you have leaved too wide gap in TX.Why?As I can remember in magnum this were 1,5 cm?
Am I right?
Thanks

[WM6]

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!!!

Thank you ivconic I very appreciate your knowledge and experiences, rely uppon your help in future too. Thanks.

zzy one more outline maybe this cross section of active coil is closer to explanation your observation.

[ivconic]

Hello,
I cant understand this.Until now I have used 2 together shielded cabels wired the way showed on your picture.But now when I read this I see many changes!So how to wire?TX and RX stat points to 2 cores,shields of cables and faradey cages all together.But then where to conec the ends of RX and TX?And on other hand how to wire to PCB?Cores to upper points for TX and RX?And leave ground point for RX empty.And conect shields of cables to TX ground point only?
If you draw a new clear picture I will be very greatefull.
Thanks.

p.s.I went prospecting yesterday with my TGS and havent found a single coin,but many rubbish colored ithems and a few large Irons afcours.But I have noticed that when I go near a high voltage line,my detector is not working!~!When I pick up my coil I can hear the electricity passing buy!!!A little bit scary.....The problem is that this is a good spot and I cant took advantage of it.
This time I had a feeling that my detector is not penetraiting!!!The land were just prepared for seeding and there were hugh level differances!May be because of this were the poor performance?

Look my sketch again and read my words again. My words justifying my draw. So what is not understandable there???

[ivconic]

Hi,
I have looked again at your pictures and I noticed that you have leaved too wide gap in TX.Why?As I can remember in magnum this were 1,5 cm?
Am I right?
Thanks

No special reason. I was too lazy to pay attention on every detail...For me not important at all.
Magnum...do i give a shi. about Magnum?! Of course not. I do make my own coils without watching other things...Simply i dont bug myself with those.

[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!

Hi,
I agree with Ivconic: when you need make a coil for a particular detector is better mathing well L , inductance, cause this way you get right frequencies at both TX and RX... but also you'll get right phase shifts when properly tuned. Both things are really important in VLF MDs cause very often there are filters and expected frequency range where device works good... outside which it works bad way or just don't work; also about phase shift you need good alignment to original coils value with no target near... otherwise you'll get bad/strange disc behaviour in disc mode.

Resistance is a key factor too cause you can alter much Q factor of coil with diameter of wire selection and total resistance value change: that's why it's often better use larger diameters on large coils.... more lenght at each turn and you need thicker wire to preserve right Q on coil.

The problem with most designs is that they require strict L matching and hi Q too and this leave really few freedom for designer when try to make very large coils or particular shapes... but here we have top class designers/experimenters ...so it's not a big problem.

Also, I noticed too that on some Tesoro's designs L is not so critical as one could expect...if frequency at the end is right (so just changing caps if required) but much more important seems is phase shift between TX/RX.

Kind regards,
Max

[Max]

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°.

Hi,
could happen so if your coin to coil diameter are "near"... please don't misunderstud me... I'm not talking about 20cm diameter coins... but of some 3cm one and e.g. a 20cm coil.

What I mean is there are conditions where, expecially with smaller coils like 8'' or 5'', you can detect a very large coin better if tilted 90° than flat. I know that... and it depends on fluxlines there and effective surface of target exposed to them... that could be higher tilted than flat in some cases.

I meant the maximum performance are flat at "far" from coil... say that you have a coil of 10'' diameter (25cm) I mean you move an e.g. 3cm diameter coin at 1.2-1.5 diameters away (30-37.5) and detect it.

In this "far" area you'll get better results with coin flat... and much probably don't detect it if tilted 90° respect to coil.

Why this ? Easy: fluxlines patern is different "near" respect to "far"; in near conditions more "lateral" coupling exist and that's why you detect better your coin.

If you tune device to extreme sensitivity... and go in "far" conditions you'll see just flat coin detection: try it.

Kind regards,
Max

[Max]

Thank you ivconic I very appreciate your knowledge and experiences, rely uppon your help in future too. Thanks.

zzy one more outline maybe this cross section of active coil is closer to explanation your observation.

Yes... exactly what I mean!

[WM6]

Hi Max

regarding this movement. How can we explain that some coils/MD give away acoustic signal only in one way movement (e.g. right movement) on return movement (e.g. back to left side) it keeps silent. This repeatedly as rule not only once.

thanks for kindness,
regards

[zzy]

Thank Max and WM6 very much,my english is poor,so i can't understand what you mean at first. thanks for your explanation,now i know the reason.

my coil is 24cm diameter.and the TX frquence is exactly at 14.6KHz.
The question is:
How many phase shift between TX/RX in you machine?

thanks for kindness.

[WM6]

Thank Max and WM6 very much,my english is poor,so i can't understand what you mean at first. thanks for your explanation,now i know the reason.

my coil is 24cm diameter.and the TX frquence is exactly at 14.6KHz.
The question is:
How many phase shift between TX/RX in you machine?

thanks for kindness.

Good question, but how do you plan to measure phase shift? Do you have 2-channel oscilloscope? If not, better forget on phase shift and do your best with coil tunning/nulling which you can perform by ordinary multimeter. On phase shift you can then make interferences in case of instability your MD.

[Max]

Hi Max

regarding this movement. How can we explain that some coils/MD give away acoustic signal only in one way movement (e.g. right movement) on return movement (e.g. back to left side) it keeps silent. This repeatedly as rule not only once.

thanks for kindness,
regards

Hi,
if you refer to DD coils could be an easy explaination: asym coil.

In a perfect DD coil the center are will always get maximum signal, independent of which side you move the target respect to it.

In asym coil (due e.g. to epoxy work or other fixing...) you can have distorted field and most sensitive area not centered but shifted or disposed in a region of space different from one side to other of the coil.

In this case could happen easy you detect better if you move the target from one side only and worse if from other side...

This could happen also in other configs like e.g. omega or also coplanar coils if not really coplanar... (asymm)

But, generally speaking, well centered and symmetrical coils give same response on symm axis with no regard of direction you move the target to it ...if left or right side I mean.

Kind regards,
Max

[Max]

phase

Hi,
yes... this is a key question... and I have not all answers about...

I measured very different phase shifts in my coils for TGS (and bandido too) but I can say that my actual coil introduce just 4° phase shift between TX/RX... so not much, and work really fine for me.

On others I get different ...also much more like 9° or more. But some worked good too on TGS ... so I really don't understand why cause I expect big variations on disc etc but I cannot notice them also using ferrite rod to test etc.

Anyway... you need lot of patience with these coils... not all works good at first glance... and some will never work good... just throw them and make new if needed till you make your PERFECT one.

Kind regards,
Max

[WM6]

Hi,
yes... this is a key question... and I have not all answers about...

I measured very different phase shifts in my coils for TGS (and bandido too) but I can say that my actual coil introduce just 4° phase shift between TX/RX... so not much, and work really fine for me.

On others I get different ...also much more like 9° or more. But some worked good too on TGS ... so I really don't understand why cause I expect big variations on disc etc but I cannot notice them also using ferrite rod to test etc.
Kind regards,
Max

Upon what we can note mayor influence of improper phase shift?
Thanks

[zzy]

Hi,
Yes, I have a good 2-channel oscilloscope.
my phase shift between TX/RX is not big,i had forgot the exactly value.
Now my machine have another question:
In disc mode, it seems have't discriminabilit,
and when working how many current your machine consume.
my machine is about 40MA. I use a 12V battery.