TESORO GOLDEN SABRE

[Silver Dollar]

The frequency should be the same as the TX.

The way it works is the receiver is purposely detuned from the transmit to avoid phase
changes. So your transmit should be 14.0 - 15.0 khz and the receiver is tuned to a different
frequency (usually 1 - 2 khz higher) but receives the transmit frequency just at a lower
amplitude (because of the detuning).

[golfnut]

3.5x20us = 14.3kHz

[sdesic]

Recorded a video of testing.
https://www.youtube.com/watch?v=vDwj...ature=youtu.be

Is this too big ferrite for this test ? or too close
I was using smaller 3-4 cm rod and it was OK.

Half dollar is not showing always - kennedy 1972 - not silver

[sdesic]

tried again - next setting GB - lost silver
and again - little bit better - used half of ferrite
no one says how many cm away and how big ferrite

next time I will use different trim pot - multiturn gives more adjusting sensitivity

tommorow - field test

[Koala]

The real ground not ferrite is whats important

I normally move the ferrite towards the coil stopping about two cm away. No hard and fast rules as long as the balance point is not at the end of the pots movement.

For best depth in disc mode set is slightly negative so there is a faint bong noise

[golfnut]

If you set geb control so you get silver but also get ferrite, then slowly back off the control so you just lose the ferrite - you should still have the silver.

If you back it off excessively to really get rid of ferrite, with margin - you may loose the silver ( as silvers response is 'late' phase wise ) and ferrite is 'early'

Sure there is no susbtitute for your local ground as that is what you will be detecting on.


I was sceptical, but I set up a
modded 14kHz Garret to ferrite and anything other than that setting falses on my soil.
same on
Un modded ACE 250
Same with my deus
Same with my IDX


my IGSL. This design was the most difficult to get going correctly and I used to not get full ferrite reject and I used to loose some metals too during construction.
It als didnt like wet grass, but this may have been how I wierd the coil and my screen. Althought it worked I never really trusted it and most hobbyists wouldnt get on on with these.


It says my soil is like ferrite.

Aincient high mineral soils like Oz I would imagine could be tricky to GEB and still get all target alloys on a dual channel device. A third channel would likely be required to geb. With CH1 to iron end and ch2 out toward siilver



I often use a few types of ferrite,

I have a small peice from an AM radio 1cm long 1cm dia
a clip-on mains filter ferrite which if quite chunky, 3cm long 1.5cm dia
a ferrite ring, painted red 1.5cm across ( generally, avoid rings for targets, but ferrite rings seem ok for GEB tests )


All of these ferrites reject with the same setting.

Distance rule of thumb dont go closer than about 2cm, as a big chunk can detune or pull the Tx or Rx loops and then the false is from the loop pull, not the kits inability to average out the single phase response from the ferrite.

[paku]

have you test enable on Disc mod then test with gold ring or gold coin

[sdesic]

I was testing today in field - 4 hours
Went to my "clean" hunted out location (hunted out with surf pi pro)
There were some false signals - one beep on swing or change of terrain (bump in ground or similar)
Found lot's of foil ;( but I wanted to find gold so I dug everything
4-5 square nails I recognised in all metal mode and rejected in disc but I have them in my bag
Found also one Celtic fibula - leftovers from more than a year of hunting
Minie ball, musket ball, few shotgun and rifle casings...
more than a fun day...

Used half of sensitivity to stabilize TGSL

I will try to find smaller ferrite - round from radio
I have one big (in video) and two halves (of same size), few circular ferrite rings

[Silver Dollar]

I'm bumming. I had my TGSL working fine on an original brown Tesoro coil then decided
to make a minelab style coil. Now it beeps like a woodpecker. Must be the 14 mh RX
picks up too much signal?. Sens doesn't do anything neither does changing the null.
Maybe the RX is tuned too close to the TX? I figured on 1.5 to 2 khz difference..

[zoomtronic]

I just were playing with coil balance using USB Oscilloscope







On RX coil i just placed function generator tuned to 14.5KHz
and that is the channel 2 on scope,
on first scope channel i connected RX coil
And moving coils across each other i got perfect null position

[manny77]

I've some questions about my tgsl:

When i firstly build it, kit contains TL071 and not LM308. I know that original LM308 was superior op-amp but non easy to find and pricey... So i mounted OP07 for u104 and u105. Not a big step ahead but probably a little better on the field. Searching for optimal op-amps i see that OP77 are something like state of the art... I have to expect another improvement or nothing so special mounting them?
I could have them easily...

OP77 datasheet:http://www.datasheetfind.com/details/1223605.html

Seeking for tgsl refinements i'm waiting for NJM2068 as frontend for rx coil, replacing LF353 (Thanks davor and silver dollar)...hope in sens benefits...

Speaking about tx oscillator, i see not perfect shape of sine wave (distortion on the top). I know that early in the forum someone investigated that issue. Anyway i don't see if a clear solution for that problem was found. Is a good, almost perfect, sinus desirable? IGSL, if i'm not wrong, has a variable resistor for R3 to adjust sine distortion. Can i apply that to tgsl edu? Which are the benefits?

Too much questions? hope not!
Thanks in advance

[6666]

Good Questions Manny, interested in the answers to.

[Jerry]

Speaking about tx oscillator, i see not perfect shape of sine wave (distortion on the top). I know that early in the forum someone investigated that issue. Anyway i don't see if a clear solution for that problem was found. Is a good, almost perfect, sinus desirable? IGSL, if i'm not wrong, has a variable resistor for R3 to adjust sine distortion. Can i apply that to tgsl edu? Which are the benefits?

Yes you can apply that to the TGSL. I tried it a couple years ago. It will clean up the TX waveform for a nice clean sine wave. However, I was not able to see any difference in performance in either air tests or in the field.

Jerry

[Silver Dollar]

I found a difference on my Bandito. A pure sine wave got a bit more in air test but
A slight distortion is better for falsing. It hits the rail and stops amplitude variations.

I made a new minelab style coil and have something funny going on with it. I nulled
it by connecting to TX and scoping the RX wires directly. I nulled it making sure to be
on the right side of null with min amplitude (10mv) but when connected to
the PCB a scope from ground to one of the RX points on pcb shows 850 mv. So I
grounded one RX wire and then got 2v! This is right where the coil wires enter the pcb
so no effect from opamp...

I ran the TX and RX wires separately and a shield wire (tied to gnd at PCB) maybe
needs the Tesoro wiring scheme?

[paku]

is that have anyone test this TGS Board
http://eversite.org/download/TGS.zip