TESORO GOLDEN SABRE

[Max]

I tried similar variations of TGS oscillator with LTSpice. Results:

 
JFet Vcutoff      Zener          Vcoil P-P
------------      -----          ---------
-.5 V              4v3             -3.5 to 3.5 
-.5 V              6v0             -5.2 to 5.2
 
-2.75 V            4v3            -6.4/-6.9 to 6.5/6.7 (instability)
 
-5.0 V             4v3            -7.7 to 7.4
-5.0 V             6v0            -7.7 to 7.4

Conclusion: coil voltage is sensitive to JFet cutoff voltage and Zener breakdown voltage. If JFet breakdown is small (-.5), can be corrected somewhat by increasing zener breakdown. If JFet breakdown is big, zener not affect - maybe lose gain control.

With JFet cutoff of -2.75, LTSpice showed significant instability, peak voltages changing. Other cases may have had smaller instability too.

The instability shown by LTSpice was very fast, every other cycle. But slower limit cycles very possible in real life.

Maybe instability not important because lock-in amp is synchronized.

JFet cutoff is important because it affects the voltage of your coil oscillation. Variations in J107 cutoff voltage would make production models of TGS have different depth. What did Tesoro do about that? Test each J107?

-SB

Hi,
original piece was TIS75, J107 is a replacement.

Kind regards,
Max

[Max]

bigfoot coils... advantages ? Anyone knows ?

Hi,
I was thinking at bigfoot coils yesterday... cause I read some interesting reports on other forums... and will like to know if anyone here tested some original bigfoot coil on TGS or other Tesoro's uMax stuff.

I know that good OO coils can be made for these uMax... but OO are large when using full diameters...

The bigfoot I have in mind is the 3x18'' one... all white...

What about that bigfoots? Are really so performative on small stuff ?

It's worth try to replicate one for use with TGS ?

Kind regards,
Max

[maxbiri]

Hi Max

Interesting yours big DD!
Is the 2 coil ovelapped 20 mm?
In yours opinion which is a good ovelapping meausure? Is a % of coil's diameter?

Thanks in advant

Bye Maxbiri

[Max]

Hi Max

Interesting yours big DD!
Is the 2 coil ovelapped 20 mm?
In yours opinion which is a good ovelapping meausure? Is a % of coil's diameter?

Thanks in advant

Bye Maxbiri

Hi,
it's something 23-24 mm inner separation from one coil to the other. Don't used a formula to get it... just tuned nulling voltage and phase for best results.

I noticed that small overlaps are good at widescan coils... I've made smaller with narrow overlap area and work very nice.

The problem is pinpointing: the coils made this way are good as widescan action but the pinpointing is difficault...often after dug soil you need external pinpointer to find the spot, and with a big coil like this it's sure you need one.

Kind regards,
Max

[miki73]

Max can you thell us,you use aluminium foil for shilding on booth coil or onlu rx coil?

Regards!

[Max]

Max can you thell us,you use aluminium foil for shilding on booth coil or onlu rx coil?

Regards!

Hi,
I use always shields on both tx and rx coils. I use, depending on what I have available or usable for that, the following as shielding material (in the order described):

1. mylar
2. foil
3. graphite varnish

Kind regards,
Max

[DIRCEU]

Hi,
I use always shields on both tx and rx coils. I use, depending on what I have available or usable for that, the following as shielding material (in the order described):

1. mylar
2. foil
3. graphite varnish

Kind regards,
Max

Hi ! MAX

I intend experiment graphite shields on TGS(L) coils.
Exactly where and when can I use coils with graphite shields?
How to conect wire or terminal on graphite?
How the high resistance ohm. stuffs work in magnetic(eletromagnetic) fields?

Thanks in advance

DIRCEU

[Max]

Hi ! MAX

I intend experiment graphite shields on TGS(L) coils.
Exactly where and when can I use coils with graphite shields?
How to conect wire or terminal on graphite?
How the high resistance ohm. stuffs work in magnetic(eletromagnetic) fields?

Thanks in advance

DIRCEU

Hi,
the graphite I used expecially in CC coils, cause it's not easy shielding all with foil or mylar in that case. Also I've used in pinpointers as well.

You can use also in other situations. One advantage of graphite is that you just need to spray it inside the housing before apply and positioning the coil(s). You need uniform surface to shield with it... very flat or with little imperfections is ok, and many housing are so, many stuff you can find this way too to employ as homemade housings.

Usually putting graphite on e.g. insulant tape is not a good idea... so you could need using a paper tape around the rubber tape before apply graphite paint.

Terminal is like in Dave Emery's article , where he employed nickel varnish (super shield) to shield the example coil. You cut some strips of copper foil or other material suitable and place inside housing with e.g. instant glue. Then leave a free space (use masking tape) for later soldering of shielding wire... then spray over the graphite varnish. That's it: when it dry you have a very good contact and can solder on copper easy.

About resistance: with graphite is higher than with foil or mylar. No problem.
You need a path for static charges discharge... and that resistance is suitable for that purpose. It could vary much with various paint kind... and if brush applied or in cans... I suggest spray can, cause it's easy and give always good results. You need resitance in the range of 1-10Kohm per cm for best results.

The scope is not blocking magnetic field... but give faraday cage to stop capacitive interaction with soil.

You often don't need gap with graphite (when high resistance) but often a 1-2mm gap you made with a strip of paper tape... I do so... you remove after like in custom cars painting the tape and leave the narrow gap there.

Kind regards,
Max

[maxbiri]

Thanks foe answer Max.

Bye Maxbiri

[Unregistered]

Max what you use on your 30cm DD coil,foil or graphite?


Regards!

[DIRCEU]

Hi! MAX

Many thanks for explanations.

Today I tested my TGS with omega coil on beach.
In ALL METAL MODE ...sensibility almost fully clockwise produce ocasional falses and detect a coin at 23 cm+_ on dry sand.
On wet sand...no conditions...many falses.

In DISCRIM. MODE sens. almost at end detect a coin at 23 cm too.(on dry sand)
On wet sand (near water) 1/3 sensibility half discrim. adj. with some falses detect a coin at 12cm+_.
Our beaches has lots of black sands and pull tabs

Regards

DIRCEU

[Max]

Max what you use on your 30cm DD coil,foil or graphite?


Regards!

Hi,
in first I've made used mylar. In this you see in the picture had just foil... so used foil.

Performance is similar.

Kind regards,
Max

[Max]

Hi! MAX

Many thanks for explanations.

Today I tested my TGS with omega coil on beach.
In ALL METAL MODE ...sensibility almost fully clockwise produce ocasional falses and detect a coin at 23 cm+_ on dry sand.
On wet sand...no conditions...many falses.

In DISCRIM. MODE sens. almost at end detect a coin at 23 cm too.(on dry sand)
On wet sand (near water) 1/3 sensibility half discrim. adj. with some falses detect a coin at 12cm+_.
Our beaches has lots of black sands and pull tabs

Regards

DIRCEU

Hi,
for beach hunting is maybe better using PI, unless you use TGS only on dry sand... which is still very good.

A simple PI could solve many problems at wet sand... but, of course, no disc.

Kind regards,
Max

[amtech2005]

TESORO GOLDEN SABRE

Max , I was told that after you finish building a vlf circuit , and it can be the Golden Sabre or Bandido or any Tesoro , that it is best to wind and make the smallest diameter search-coil possible 4 to 5 inch or less !! The smaller the TX field the better , and this will help to align , test or correct any circuit problems . And then this will eliminate Chatter when the gain or sensitivity is at maximum with a full size search-coil . We all have our personal alignment or test proceedures . But maybe when we slap on a big Search coil right away , that is a big mistake ???? Smallest search coil first , then we calibrate or test with maximum gain at minimum noise , then we increase the coil size and re-check the gain , noise , and Tx waveform . I wonder what size search-coil Tesoro does on its initial tests at the factory ?? Maybe they use a Tiny 2 inch I.B. dummy coil and do a sweep analysis right before the audio IC ???........... Take Care........Eugene

[Max]

Max , I was told that after you finish building a vlf circuit , and it can be the Golden Sabre or Bandido or any Tesoro , that it is best to wind and make the smallest diameter search-coil possible 4 to 5 inch or less !! The smaller the TX field the better , and this will help to align , test or correct any circuit problems . And then this will eliminate Chatter when the gain or sensitivity is at maximum with a full size search-coil . We all have our personal alignment or test proceedures . But maybe when we slap on a big Search coil right away , that is a big mistake ???? Smallest search coil first , then we calibrate or test with maximum gain at minimum noise , then we increase the coil size and re-check the gain , noise , and Tx waveform . I wonder what size search-coil Tesoro does on its initial tests at the factory ?? Maybe they use a Tiny 2 inch I.B. dummy coil and do a sweep analysis right before the audio IC ???........... Take Care........Eugene

Hi,I think they use the 5'' as reference during tests... but maybe smaller ? Don't know.... just remember they have the 5'' around... used for trashy sites... probably they prefer using it at the end.The larger the coil the more the noise... right: this is expecially about 50 or 60 Hz noise entering the big RX... much more easy than on smaller ones, I know.But I'm lucky with the 30cm DD cause it gets just a little more than 10''DD , standard coil for homemade TGS.If you rise gain to max in my big TGS you can spot some chatters from time to time... with monostable ON you notice that.But there's a silly trick: rotating the notch pot (even when notch is disabled) you can reduce and about totally null that effect.

Kind regards,
Max