BandidoII DISC phase shifter LOOK at this!

[Unregistered]

Hello Max,

Like I sad, relax, your on the good way, the dd coil works well.
There can be some more sens, ad some extra rx windings on the tx coil.
Works like a trafo, like in the open centre coils. Experiment.
For briks and stones that are having some iron in it .....it is hard, and for the tesoros it is not possible.

Good luck

[Max]

Hello Max,

Like I sad, relax, your on the good way, the dd coil works well.
There can be some more sens, ad some extra rx windings on the tx coil.
Works like a trafo, like in the open centre coils. Experiment.
For briks and stones that are having some iron in it .....it is hard, and for the tesoros it is not possible.

Good luck

Hi,
yes...I'm relaxing with my DD coil...you are right for 0.30mm wire!
I'll try to follow your advices.
Unfortunately bricks-pottery-ceramics are just in some interesting fields...and that's boring for me to dig holes in hard ground to find just pieces of bricks.
If with tesoro is not possible to avoid this...question is :
- is it possible to avoid bricks-etc with a decent performance detector ??? (I mean for small objects search like coins, ring etc) If so, wich detector or kind of detector can do that search regardless of pottery-bricks ???

Best regards,
Max

[Unregistered]

Hello Max

The tesoro's, I made copy's from, all have problems with large rusty iron and large stones that have some iron in them, I was thinking of large briks that were used for buildings and streets.
Thats different form your pottery, next can help?
You can tray to make some adjustment in the ground preset, this is a very importend adjustment. In the past I was searching with a family member...(my sister!) she was finding large silver coins Philips from Spain !! I dit NOT detect them : all to blaim the ground preset I made in the golden !!
The cap that is used in this ground circuit, (some times in schematics 150 pf) must have a lower value :15 to 30 pf ( I never made the bandido uMax so dont now for this circuit ). You can make some tests with the pottery that makes your problems, take some home and make ground preset adjustments. Also look at the amplitude from the first opamp, making a extra meter circuit that shows ampl. fall and rise can give some indication ???

Now making the 1280, the first test : small, thin gold is a problem (not detecting it), test with large building stones: it is also detecting them, made the first tests with DD 20 cm coil. Many adjustments but the low freq. is interessting.

Best regards and good luck

[Max]

Hello Max

The tesoro's, I made copy's from, all have problems with large rusty iron and large stones that have some iron in them, I was thinking of large briks that were used for buildings and streets.
Thats different form your pottery, next can help?
You can tray to make some adjustment in the ground preset, this is a very importend adjustment. In the past I was searching with a family member...(my sister!) she was finding large silver coins Philips from Spain !! I dit NOT detect them : all to blaim the ground preset I made in the golden !!
The cap that is used in this ground circuit, (some times in schematics 150 pf) must have a lower value :15 to 30 pf ( I never made the bandido uMax so dont now for this circuit ). You can make some tests with the pottery that makes your problems, take some home and make ground preset adjustments. Also look at the amplitude from the first opamp, making a extra meter circuit that shows ampl. fall and rise can give some indication ???

Now making the 1280, the first test : small, thin gold is a problem (not detecting it), test with large building stones: it is also detecting them, made the first tests with DD 20 cm coil. Many adjustments but the low freq. is interessting.

Best regards and good luck

Hi,
thanks for the hints. I found that every vlf I've used till now suffers from bricks-pottery-ceramics detection. Not in the same way of course...but always I can detect bricks and fragments, sometimes also small ones.
I was shocked by goldscan4 ability to detect pieces of them at incredible distancies I never seen before...also with other PI machines.
At the moment I have 3 PIs working, my homemade bandido and a classicIII and all of them detect bricks quite easy.
Think that both VLF/IB and PI kind of detectors suffer that problem, with conventional coils for them...not with special arrangments like separate big tx coil on the ground and portable rx coil like one can do with PI type...taking rx coil more above from the ground level (10-15cm are good for this).

I've made test in past with Two-boxes and avoid much problems but this stuff works with larger objects...and are not always reliable.

Also BFOs and BFOs-PLL suffers from bricks detection...

One my friend as a Minelab unit that suffer too of bricks detection...wow

What to say...it's not an easy problem to solve I think...and I'll wonder if someone have solved also in any good handheld detectors !

Someone knows if there is such kind of "immune" detector ???

Best regards,
Max

[Max]

Errata corrige: my caps are Carl's second set !

Hi all,
I'm sure now that 130pF is wrong there as Gary stated. I found having 22pF is right to reproduce goodrat's diagrams for that part of the circuit.
Also with 22pF I get near-to-total iron disc as bandido II must have when in disc mode. Imbalances occourrs only when masses of iron or sheets of it are really close to coil then perturbating too much filed lines.
So I think that the magic number is 22 !

It's interesting the use of 100Kohm resistor to modify phase shift but I think that this way one can go easy out of disc for iron and then failing rejecting it.

I don't know if is a good idea to have 30pF there...maybe if you NT change cap to 22pF you don't need resistor but just original pot.

Now I'm happy with disc (values of caps are the goodrat's sets present in Gary's revised schematics) and just play with some depth gain...using DD coil design.

I've just realized a DD of 22cm diameter like this:
120 turns tx 0.30mm wire tuned to 10KHz
120 turns rx 0.30mm wire

Both are about 23ohm in resistance.

Used tape for first wrap...then mylar/al for shields (wrapped too) then again another winding with electrical tape.

I get 2eur coin at 30cm in disc mode...and 32 in all-metal...and that's fine for a 22cm coil ! Yes...I lose pinpointing...and have to deal with the DD sensitive area under overlappings...but wow it goes deeper than with concentric round 8''. DD was really easy to make for bandido using that data...and really effective!

Much less noise with mylar shields...just get a little down in frequency to 9.860Hz...but seems not a problem. Disc works fine and deep !

Best regards,
Max

Hi all,
JUST A LITTLE CORRECTION ON WHAT I WROTE FOR THOSE CONFUSED THAT NEED TO BUILD BANDIDO II UMAX:

"Now I'm happy with disc (values of caps are the goodrat's sets present in Gary's revised schematics) and just play with some depth gain...using DD coil design."

WAS AN ERROR, I MEANT CARL'S SECOND SET OF VALUES THAT IS:
C16 : 39pF
C10 : 22pF
C14 : 8.2 pF
C13 : 10pF
C18 : 22pF

I've got that values from Gary's revised schematic and in a earlier post he said:

"Those Values were given to me by "Carl Moreland" in an email to me.
He said he measured them Out of Circuit.

On the Other hand "Goodrat" emailed me and Said he measured a Tesordo Detector.
C10, 13, 14 and 18 were all 5pF.
C16 and C29 were 10nF.

So take your choice."

With these values I get the same goodrat's diagrams but CAPS VALUES ARE THE LISTED ABOVE NOT 5pF or 10nF as goodrat mailed to Gary.
I think they are absolutely right
I'd like to send many thanks again to Carl for pulled up them and measured out of original SMT circuit of bandidoII uMax though he can't guarantee these are right values. I think they are.

I was confused cause got the same diagrams that goodrat posted in a previous post but with these values Carl sent to Gary not with goodrat's values.

Best regards,
Max

[chemelec]

Hi all,
JUST A LITTLE CORRECTION ON WHAT I WROTE FOR THOSE CONFUSED THAT NEED TO BUILD BANDIDO II UMAX:

"Now I'm happy with disc (values of caps are the goodrat's sets present in Gary's revised schematics) and just play with some depth gain...using DD coil design."

WAS AN ERROR, I MEANT CARL'S SECOND SET OF VALUES THAT IS:
C16 : 39pF
C10 : 22pF
C14 : 8.2 pF
C13 : 10pF
C18 : 22pF

I've got that values from Gary's revised schematic and in a earlier post he said:

"Those Values were given to me by "Carl Moreland" in an email to me.
He said he measured them Out of Circuit.

On the Other hand "Goodrat" emailed me and Said he measured a Tesordo Detector.
C10, 13, 14 and 18 were all 5pF.
C16 and C29 were 10nF.

So take your choice."

With these values I get the same goodrat's diagrams but CAPS VALUES ARE THE LISTED ABOVE NOT 5pF or 10nF as goodrat mailed to Gary.
I think they are absolutely right
I'd like to send many thanks again to Carl for pulled up them and measured out of original SMT circuit of bandidoII uMax though he can't guarantee these are right values. I think they are.

I was confused cause got the same diagrams that goodrat posted in a previous post but with these values Carl sent to Gary not with goodrat's values.

Best regards,
Max

One thing I would mention is that just Parallel PCB Traces could add 5pF or More in places.

So Unless your actually Using an Origional Bandido Board, its probably anyone guess to Correct values.

[Max]

One thing I would mention is that just Parallel PCB Traces could add 5pF or More in places.

So Unless your actually Using an Origional Bandido Board, its probably anyone guess to Correct values.

Hi Gary,
yes that's true. Also smd components have always better tollerances than most other normal ones...and this is another factor to keep in mind expecially for cap...where tollerances are often higher than e.g. resistors used (1%).
I think that thos values are anyway ok...cause in testing I get exactly same diagrams as goodrat posted...and Carl pulled out that caps from the circuit to measure more exactly.
I've noted that also a wrong shield on coil have a drammatic effect on disc.
Really difficault to make good bandido clones without SMT and good coils.

Best regards,
Max