Italian VLF design

[ivconic]

Totally agree too.
Having the Deus for ~7 years i can now remember many oldies that i had in the past and compare what i did than with them and now with present one.
I am totally sure that some oldies will perform the same or even better than most modern ones , on some sites that i know.
Sometimes too many features is not the advantage but is disadvantage.
Short practical example:
My hand-made TGSL was totally deaf on irons. So as on few "desirable" alloys too.
Yet it was super sensitive on small silver coins.
So , when i purposely go to site when i expect to find silver coins; all i need is my TGSL.
So i start walking in total silence. I can walk like that for 50-100 meters.
Once it makes sound; i am sure it is silver coin. On that particular site.
And what happens with the Deus there?
I got so many "squeeks&squaks" .... "warooom-warooms" and "teee-tats" on literally each step that i make.
It simply "feels" everything.
Than curiosity starts itching me madly. I must dig out and see what is all about.
99% junk.
So at the end of a day i am totally exhausted from digging, having overall less silver coins that what would i have with silent TGSL.
And whats better more ; with TGSL i wouldn't dig so many holes that day. Nor i would get sick from constant squeeky music all day long.
...
Now.. i am not saying TGSL is better than Deus (i bet there are few malign cretins to notify this and place bedlam of replies... actually i can think now only on one ultimate cretin to do something like that)...
So no, TGSL is far even from been competitive to Deus. No way. Deus is superior in all possible aspects, of course.
But at the end of a day , on some specific sites; fact is that i am more happier with TGSL.
Or 1265... or 1266... or 1220B... depends on exact site, on the first place.
...
Of course, powerful as it is, the Deus, also so rich with features and various adjustments; very easy could be set and adjusted to totally mimic the poor TGSL behavior. Of course.
But... who on Earth will do something like that, having such a beast in hands?
Not me. For sure. I tried. No help.
Curiosity will itch me to death... and than i start "turning knobs" wildly!

[dom44]

I agree with you sinclairuser here in Australia minlabs are the holy grail in detectors people use them a few times then on sold, they think the more you spend on a detector the better your chances you just can't go past the time tested method of research your area and learn your detector. the best books I have read on treasure hunting was "The Treasure Hunters Manual" By Karl von Muller no longer in print this also applies to metal detecting, He has found a lot of valuable treasure and states its 90% research and 10% finding it.

[sinclairuser]

i find it fascinating that with all todays technology and advances these simple early vlf's still do the business.
well designed well built detectors are timeless.
having said that some folks over in the USA still have a place for old bfo and tr's too, i suppose a good basic well built unit will always find stuff, add to that 30/40 years practice with it and they shine.

iv'e personally seen old fishers, tesoros, cscope and whites machines pull finds out of a spot supposedly "cleaned out" by xp deus and other modern detectors.
on any ground and old fella with his trusty old Red baron will find more than a novice with a deus simply because he has learned the nuances of his machine, add the skill of years of detecting and that is why so many old guys find these UK hoards, on well detected ground.

some of these "old" designs were always good but there is a skill to using them properly.

[dom44]

here is the sprint file if anyone wants it http://s000.tinyupload.com/index.php...38661501642492

[ivconic]

If i recall correctly; initial idea was not to make it "concealed" but underwater.
Also i stand corrected; it is not directly TGSL but more likely Silver Sabre version.
Things are too similar with those early Tesoro models.
I did them all. Also made many "strip down"-s.
So i take them all as pretty much one and same design.
Despite the fact that those are very early models, 30-40 years old; those are still "champions" on some soils and types of sites.
Panonia area (divided between Serbia, Croatia and Hungary) is well known area of best leveled agriculture plowing soils.
Also very well known by rich historical and archeological sites.
Most frequent finds are small and smallest silver coins. At the same time; that soil is heavily polluted with various ferro-originated junk.
Above all; heavily mineralized due long term chemical agricultural treatments.
Coins and other desirable finds are mostly up to 20cm depths. But totally covered with "chemistry", masked and polluted.
So... during the years i am getting very positive reports from hobbyists on some detector models ... as well as very negative reports on some other detector models.
Whats very indicative is that early Tesoro models are performing great under such conditions.
Many ... indeed many people are still using those models with great satisfaction.
Nothing is "obsolete" as long as it is doing the job fine.

[waltr]

dom44
Thanks for posting readable schematics.
Yes, this is very nearly a Tersoro.

[kt315]

DB seems we must refresh our loved topic on winter

https://www.geotech1.com/forums/show...etector!/page2

[dbanner]

longboard doing ApBerg underwater. Italia is not country where you can free hunting on beach. you must cover up
the detector in wine paper pocket/bag, on land, or in pants in case you are in cops' view, in water.

I see, so he had intended to conceal the device, hence the longboard design. He could hide it in his underpants, but where would he put the coil, up his a...?

[dom44]

thanks kt315 excellent information i am sure it will be helpful and some of the tesoro circuits you posted i don't have thanks.

[kt315]

The best part about this circuit is the long board layout. I love it.

longboard doing ApBerg underwater. Italia is not country where you can free hunting on beach. you must cover up
the detector in wine paper pocket/bag, on land, or in pants in case you are in cops' view, in water.

[dbanner]

Very nice PCB to stick into PVC pipe housing. Niced job dom44.
This is obviously a tesoro circuit. The TGS/royal sabre are very good detectors as far as sensititvity is concerned. This circuit is a stripdown of those. So performance will be comparable, if you can source a stock coil, even better.
The best part about this circuit is the long board layout. I love it.

[kt315]

tesoro pantera-royal sabre-GMT king cobra, amputated certainly to tesoro amigo-compadre. new? not.
all you say thats new is long forgotten old. negative voltage generator was to generate TWO tones, in right full schematic.
that we call NOTCH FILTER, that was insolently cutted in this 'new light tesoro one'.

PS. this is sure tesoro silver sabre I.


Re: Silver Sabre circuit ***IMPROVEMENTS***
Posted by Sean Goddard
Wednesday 10 April 2002, 11:33:00
In Reply to Re: silver saber circuit - Posted by Carl on 4/04/02

You could try different Op-Amps in the SS circuit, but if you look LONG and HARD at the existing ones, you wont find any which are better them in the areas which matter most.

You COULD try ones like the National Semiconductor LF353N (MUST be the N, as it's an "improved" version of the standard LF353.

I believe there's a newer version of the '442 as well which has better a current noise figure.

The "bottom" signal path has a constant retune and Isuspect is the "motion" path. Changing the time constants of the two "auto balancing" circuits i.e. the LF442 and the LM358 blocks, simply involves changing BOTH the 330K resistors.

You could try starting at 470K. This will "theoretically" give you better sensitivity to small items. Too high a value, and you will "smear" the motion signal.

Also, changing the value of the two 150K resistors on the "front end" LF353 to 330K will give a marginal improvement in depth and sensitivity, but too much will make the GB setting a LOT more critical, as well as making the detector VERY unstable.

Replacing the TIS75 VERY CRUDE synchronous demodulators with REAL "full time" demodulator circuits which also sample the negative portion of the target signal, will SIGNIFICANTLY reduce the system noise levels and drift, and make a much more stable machine.

Other methods are to amplify the incoming signal, and phase shift the ground and discriminate signals DIRECTLY, this means that you could dispense with the "wandering" Colpitts type TX oscillator in the top lefthand corner, and drive the thing with a crystal (VERY STABLE) one. Using a buffered take off of the coild drive signal for the Demodulator switching signal also reduces noise as it eliminates clock "jitter".

Finally, use "metal oxide" resistors THROUGHOUT, they're a LOT quieter than the cheap carbon ones used by Tesoro, and use OFC cable to do ALL the link-up. Keep ALL cables as SHORT as possible, and use screened cable if you can, only connect ONE END of the screen when running a single wire to controls, this will avoid creating multiple paths for any noise picked up on the screening, also connecting the screens at ONE COMMON point in a "star" ground will also help.

I could list over 30 simple and immediate improvements which took me just over two hours to come up with, but Tesoro aren't going to pay me for them.

Hope someone finds this info useful.
---
Sorry I don't have time right now to go into all the details of the improvements which have been suggested. Most of them will not improve anything, or will screw up things that are already good compromises.

The Silver Sabre circuit is one of the most successful beeper platforms in this industry. I think it dates to about 1986, and products which are very nearly the same thing are being manufactured today. Admittedly it is not particularly sensitive, but it is easy to build with readily available parts, and has an excellent discriminator.

I recommend building it just the way you see it on the schematic, using a purchased Tesoro searchcoil. If you happen to know how, you might want to substitute CMOS switches for the JFETS, which however is not likely to improve performance. If you're using a Tesoro coil of the specified type, I would discourage you from attempting to operate it at a different frequency or using a crystal controlled transmitter: although conceptually easy, there are many potential pitfalls in doing such things, which are not obvious.

Attempts to increase the sensitivity of this circuit are likely to either fail, result in only slight improvement, or cause other problems (which may not be obvious at first). If a person is striving for high sensitivity, the Silver Sabre is not a very good foundation for such a quest.

If, once you've gotten the circuit to work satisfactorily, you want to play around with it, the easiest thing to do is add simple "features", for instance an external ground balance knob and a switch to disable discrimination.

[dom44]

I thought it was very clever the way they used the negative voltage generator to generate the tone as well keep the part count down, that's what caught my eye first and threw me off from working out it was TGSL

[ivconic]

"Drawn: Ap".
So it is ApBerg.
My memory serves me well after all.
From time to time...

[ivconic]

to hard to keep track of them all ivconic this version has a nice pcb and does work well
handy for a small portable unit.

Yes it is.
Whatever applies to TGSL; applies to this one too.
Since i got it from Nakky or ApBerg; i would call it "Dutch version", although "Sceatta" resembles on Italian.