TGSL Tuning & troubleshooting

[simonbaker]

better test

I think I was too hasty with my first tests in my workbench with dfbowers TGSL -- or the noise has subsided.

With careful adjustment of sensitivity and a little chatter, it looks like I can get detection with Euro close to 30 cm, and quite solid at 20 to 25 cm. So I it proves that dfbowers MD is very solid and quiet compared to what I have constructed, and it means I should continue to work on my circuit and make some solid finished coils to test with, and make sure the cable is good.

Update: I think the reason I get better results today is that I'm orienting the search coil on its side, perpendicular to floor. If I make it parallel to floor, I get bad results again. So some particular noise vector here it seems. Funny .

Q for dfbowers: just for the heck of it, would you try an air test with your coil parallel to the ground, but around a meter off the ground? And maybe some other directions?

-SB

[dfbowers]

I think I was too hasty with my first tests in my workbench with dfbowers TGSL -- or the noise has subsided.

With careful adjustment of sensitivity and a little chatter, it looks like I can get detection with Euro close to 30 cm, and quite solid at 20 to 25 cm. So I it proves that dfbowers MD is very solid and quiet compared to what I have constructed, and it means I should continue to work on my circuit and make some solid finished coils to test with, and make sure the cable is good.

Update: I think the reason I get better results today is that I'm orienting the search coil on its side, perpendicular to floor. If I make it parallel to floor, I get bad results again. So some particular noise vector here it seems. Funny .

Q for dfbowers: just for the heck of it, would you try an air test with your coil parallel to the ground, but around a meter off the ground? And maybe some other directions?

-SB

Simon,

I never really thought about it. At times I would move the coil 360 degrees to try to isolate sources of noise but could not pin point anything. Also, I have found that hidden airducts and metal construction materials in the floor and walls have some bearing on testing. Most on my test were done with the coil in a vertical plane, parallel to the walls. I have a basement that is sub-terranian with a concrete floor that makes a good testing location but I have to wait for TVs and PCs to go off upstairs.

I have had absolutely fantastic results relic hunting though, a good quarter mile from any structures at all. The unit functioned just as good as any store-bought unit.

One detector in my arsenal, the Shadow X5 is really noise sensitive as well, more so that the TGSL. Somethimes it barely functions in the house at all.. but outside is completely different.

Head to the beach!!

Oh.. try testing very early in the morning before anyone has had a chance to turn on any electrical devices.. you may notice a difference as well'

Don

[Vladimir]

I think I understand. It looks like audio cables with RCA connectors. Each pair of wires is one shield and one inner wire.

The reason I ask is that I have used the same cable types sometimes.

But I think maybe there is a problem with these, depending on how much noise is around.

Here is why:

I think the TX cable is OK. It is the RX cable that may be the problem.

The reason is that because the LF353 is a differential amp, it should ignore common mode noise signals.

But if we use a pair of wires where one is the shield, then I think noise affects the wires differently, because the outer wire shields the inner one. So maybe the differential amp picks up the noise differential.

It seems like a twisted pair inside a separate shield might be better. Any noise that gets through the shield should affect both wires equally, and then be ignored by the diff amp.

However this is complicated by the fact that one of the RX wires is grounded at the coil shield. In that case, maybe the audio cables are best after all?

I'm really am not sure what is best. You seem to get good results with audio cables, but you also made mods to reduce noise.

I find the cable wiring difficult to understand, especially the grounding of the RX coil in the shield. I wonder if differences in cabling is causing some TGSLs to be more sensitive to touch or feedback beeping. I think there needs to be some testing of this, and check what cables we use.


-SB

I have tried to use the cable that was recommended Ivconic, the noise level was similar as before. My thoughts go in the direction that the number of turns in the Rx and Tx do not have a good relationship. I tried with coil 2x61 turns and got worse sensitivity (4-5 cm less). But the noise was considerably smaller.


regards

[simonbaker]

Simon,

I never really thought about it. At times I would move the coil 360 degrees to try to isolate sources of noise but could not pin point anything. Also, I have found that hidden airducts and metal construction materials in the floor and walls have some bearing on testing. Most on my test were done with the coil in a vertical plane, parallel to the walls. I have a basement that is sub-terranian with a concrete floor that makes a good testing location but I have to wait for TVs and PCs to go off upstairs.

I have had absolutely fantastic results relic hunting though, a good quarter mile from any structures at all. The unit functioned just as good as any store-bought unit.

One detector in my arsenal, the Shadow X5 is really noise sensitive as well, more so that the TGSL. Somethimes it barely functions in the house at all.. but outside is completely different.

Head to the beach!!

Oh.. try testing very early in the morning before anyone has had a chance to turn on any electrical devices.. you may notice a difference as well'

Don

I will definitely enjoy testing in the field - looking forward to it.

I had this off-the-wall idea that maybe there were some long-range, extremely low transmissions confounding me... read "submarine communications". There is a big installation a few hundred miles north of here, who knows what locally, and I believe you've got one over in Virginia. But they would affect outdoors as well as indoors, so your field tests nix that idea.

I'll keep dividing and conquering as you recommended earlier.

-SB

[tragac3]

cable

Best cable for TGSL is double coaxial such as Vladimir is shown, it has been proven many times .

[simonbaker]

Best cable for TGSL is double coaxial such as Vladimir is shown, it has been proven many times .

I don't think Tesoro uses such cables though, maybe for a reason.

Regards,

-SB

[Vladimir]

I don't think Tesoro uses such cables though, maybe for a reason.

Regards,

-SB

Hi Simon
We have already proved that the original Tesoro, modifications are better ... why not accept that they have a mistake in the choice of cable?
I would never replace my TGSL for Tesoro TGS.
Regards

[simonbaker]

Hi Simon
We have already proved that the original Tesoro, modifications are better ... why not accept that they have a mistake in the choice of cable?
I would never replace my TGSL for Tesoro TGS.
Regards

Yes, I accept that as possible. It would be nice to test it somehow too.

Regards,

-SB

[Vladimir]

Reason:

[simonbaker]

Reason:

Don't forget most of those Tesoro MDs use a concentric coil, which is really preferable if you can get the same depth.

Regards,

-SB

[Vladimir]

I know that, but with the DD coil I got a better sensitivity (# 209). The self-construction is difficult to make a good concentric coil.
Regards

[simonbaker]

I know that, but with the DD coil I got a better sensitivity (# 209). The self-construction is difficult to make a good concentric coil.
Regards

Right - but that is probably a major reason TGSL beats Tesoro TGS in those charts, because of coil, not design.

But I always say if you get great results with whatever design, cable, coil you use, that is what counts. Your's works nicely. I just like to try to learn which individual parts may be superior, not always easy.

Regards,

-SB

[Vladimir]

You are right, it was necessary for almost two years of patient work that I got a usable and a good detector, try on the table and then the real ground, again and again. The final conclusion is that the problem is in the coils, the design also can be improved. After 15 years of working with metal detector, now I see how little I know.
Regards

[dfbowers]

I hope it's a good explanation?

Vladimir,

On the RX circuit, do you ground the shield inside the box or is it tied only to the shield in the coil?

[Vladimir]

Vladimir,

On the RX circuit, do you ground the shield inside the box or is it tied only to the shield in the coil?

On the coil and the board.