SMT Bandito Info/Build

[Silver Dollar]

Hmm I'm looking to tune the coil a bit but am confused. The TX is around 10 khz but the RX calculates to 10.867 khz.
On TGSL the TX vs RX frequency is about 1.5khz difference...

[Koala]

Well I saw 16" and loud audio with the TGSL once but I'm back to using the SMT Bandito
as it fits in the Tracker case. The plan is to get the coil working then tweak the board a
bit more and see what it can do. I tried the Minelab oscillator but couldn't get the AB+C
mode working as not enough -5V. The Original Bandito is still less noisy too, I'm not sure
how to fix that. Reading the TGSL thread again it can be the pot, the coil, the board or most
anything. It can go away for 45 minutes then come back etc....

Experimenting I had echoes in the taget signal, sustained tones after detection and rhaspy
tones. There's a lot going on there. It's like a fractal thing the closer you look the more complex
it gets! Well I think it will be usable as is. I'll try it on real ground soon and see what happens!

I mainly used the center tapped coil as making a sheild is tough! I have some shielded coils that
don't fit in the housing! You loose 1 or 2 DB with the centertap but gain the loss with shield so
is probably a wash. I just hope it is OK on wet grass...

I thought I understood how things worked on these devices but found the real world sometimes acts
differently than you expect. For instance I was playing with the 4.7uf caps on the TGSL. I matched a set
with the highest value I could find (To get the lowest frequency so as to let more signal through). The
matched ones were 4.5uf but the ones I took out were 4.9uf! I tried the 4.5's and they seemed to work better!

Don't forget the original Bandido II µmax had a red zone at the end of the sensitivity knob and if you use the machine in the red zone you get an occasional beep.

I agree that getting the shield right is hard. Depth isn't everything out in the field stability and target separation are equally as important.

[Silver Dollar]

Well I saw 16" and loud audio with the TGSL once but I'm back to using the SMT Bandito
as it fits in the Tracker case. The plan is to get the coil working then tweak the board a
bit more and see what it can do. I tried the Minelab oscillator but couldn't get the AB+C
mode working as not enough -5V. The Original Bandito is still less noisy too, I'm not sure
how to fix that. Reading the TGSL thread again it can be the pot, the coil, the board or most
anything. It can go away for 45 minutes then come back etc....

Experimenting I had echoes in the taget signal, sustained tones after detection and rhaspy
tones. There's a lot going on there. It's like a fractal thing the closer you look the more complex
it gets! Well I think it will be usable as is. I'll try it on real ground soon and see what happens!

I mainly used the center tapped coil as making a sheild is tough! I have some shielded coils that
don't fit in the housing! You loose 1 or 2 DB with the centertap but gain the loss with shield so
is probably a wash. I just hope it is OK on wet grass...

I thought I understood how things worked on these devices but found the real world sometimes acts
differently than you expect. For instance I was playing with the 4.7uf caps on the TGSL. I matched a set
with the highest value I could find (To get the lowest frequency so as to let more signal through). The
matched ones were 4.5uf but the ones I took out were 4.9uf! I tried the 4.5's and they seemed to work better!

[Koala]

Sounds good my IDX gets just under 16" with a 27cm DD but looses lots in the ground.

Ivconic made both normal and center tapped and found the normal had more depth but center tap had better discrimination but that detector originally designed for a center tap coil.

[Silver Dollar]

Well I did some testing today. I had cut the original cable as it was 8 foot long and
I put a connector on it today and tested the Original Bandito and the SMT one.

The Original wouldn't ground balance on a piece of ferrite but might need an internal
adjustment for the new short cable. But it got;
9 - 10" Gold
12" Silver
All Coins 9"

The SMT Bandito nulled ferrite ok and got;
10" - 11" Gold
12 - 13" Silver
9" All Coins

With the new 9" DD coil I just made;
10" - 11" Gold
11" - 12" Silver
9" - 10" all Coins

The new coil is a 6.0 mh TX and 6.5 mh RX center tapped with no shielding. Some random beeps were
apparent. Here's a picture;



The null was around 200 mv at pin 7 of the first opamp but went way up while the hot melt was applied
then back down to 73 mv after it cooled. That might be too low. We are aiming for 4 mv at the coil which
should be 200 mv at the output of the first opamp. I saw 500 mv with the original coil...

[mschmahl]

Here is a link for the german forum http://www.detektorforum.de/smf/eige...-t54227.0.html where firebox write some info´s.

[Koala]

Firebox http://www.youtube.com/watch?v=1HiHej59W2Y do not look to shabby even though its maxed out. Homemade coil by the look of it and minelab mod visable on the board.

Even with any mods the Bandido ii µmax should out preform the original Bandido for depth slightly either something amiss with the board or we don't know the correct specs for the 5 pin µmax coils.

[Silver Dollar]

It's funny when I work on the TGSL I wish it to be more like Bandito and when I work on Bandito I
wish it to be more like TGSL!

I decided to use the TGSL TX coil and 14.7 mh RX but then thought of swapping to the Minelab
oscillator and then remembered the TGSL doesn't fit in the Tracker housing. So I tried the Bandito
on the TGSL TX/14.7 RX and it performed poorly! A few inches less than the TGSL on most things.
(I got 16" on silver on the TGSL on one test!). But that's the board I will use in the Tracker housing
so I have to make it work with a new coil.

So I'm going to put the Minelab oscillator on the Bandito and try a few combo's to see how good I
can get it. Note: I ran the original Bandito on most of these coils and it worked much better than the TGSL
or SMT Bandito. It had less random beeps and better than SMT Bandito depth but a bit less than TGSL.
All in all a factory unit and coil is hard to beat!

[Silver Dollar]

Yes the new coil is a 9" DD. Using the exact same inductance's/resistances and even the
same cable (stock was 8' I cut it down to 4' and am using 1/2 for new coil) I get much less
depth, I'm not sure what's going on...

I like thinner shielding but found it too hard to work with thin mylar as it kept breaking. I used
some mesh screening on another coil that worked good but added a lot of thickness to the coil
(It has to fit in the housing and be slightly movable). I had kitchen ALU foil on this one but took
it off thinking it was killing my signal...

[Koala]

Well using the 34.5 mh coil and retuning the RX a bit I get 13 1/2" on silver and 10" on Gold.
Coils are a bit lower though and there's occasional chatter but not too bad. The sound is a bit
ragged and not as punchy as the original coil. Not sure if I should try to null and pot this coil or not....

Are you making 27 DD If so I would expect the home made to surpass the original for pure depth. Always amazes me how much depth I get with an original whites 8". Having said that the coil is well nulled. Only a few millivolts on the output of the amp. Have not looked inside but suspect that a piece of graphite has been used. The sine wave is very choppy which is what i get if a piece a graphite between the two coils of a DD.

I have always used a space blanket for shielding again not as good as the original. Fine 95% of the time but in some conditions get an occasional chirp. Must be shield as on dry powder sand it work 100%. Not happy with the space blanket method because over time it starts to fail. Must be some sort of oxide forming or breakdown of the blanket