End of the Mineoro link on youtube

[WM6]

Originally Posted by ivconic

A

Actually; i always wanted to read detailed technical explanation about TM808 design.

The problem with these T/R searches is that you can not have anything metallic on you, otherwise you alone generate false signals. So a plastic digging tool or hunting for two.

[ivconic]

Originally Posted by WM6

The problem with these T/R searches is that you can not have anything metallic on you, otherwise you alone generate false signals. So a plastic digging tool or hunting for two.

I am awared of that.
I am interested in precise explanations of it's working principles. Not generally explained, but in exact details. For example; i would like to know how they calculated coupling relation between Al loop and small coil inside it? What relation? What is resonance of Al loop? What happening if loop was with different sizes? What are merrits and what drawbacks from such coupling. Is loop size dependable on working frequency and how? How possibly that loop can be suitable for such low frequency? Is it the coupled coil the one which solving that issue?
Working frequency in relation to all of that? Etc..etc...

Wild guess: instead Al loop, why not use another coil coupled with existing one on ferrite rod? Depths will be lower but better directional sensitivity maybe achieved? Other type of coupling? Coil?

Following simiillar logic we can come to conclusion that any other nonmotion metal detector can also be easilly adapted to work as 2 box? Right or wrong?

[Esteban]

Originally Posted by ivconic

Actually; i always wanted to read detailed technical explanation about TM808 design. Not manual, not review - but details about electronic stages, roles of each stage and idea of design itself.
I can not say that i don't know how 2 box supposed to work, i know some details of course. But i would like to see and read facts from designers. Pitty i never saw anything simillar. I like Payne's articles just because he talks pretty straightforward and it is easy to learn from him. I can say that also i liked Carl's articles on HH subject; also straightforward and understandable. Andy Flind also, Don Lancaster also. But majority of others are writing pretty general, hard to learn details.
So speaking of TM808...Esteban..you would be mostly on your own, when designing such coils..

I can point you on "Deep seeking metal locator" by Phil Wait and Roger Harrison, i beleive you already saw that project. There you can see pretty good explained coil & loop coupling, for such matters that you are planing to explore...

I found very interesting the Phil Wait and Roger Harrison project. Tank capacitor, mechanical adjustment for zero, tune capacitor and other points are very delicate here. When persons construct it, they forget that is extremely important the final adjustment. Here the most failed.

Anout TM808, maybe in patent are explained function of each stage. We have schematics of this, also PCB in SMD version posted here few years ago... Now, somebody built it and wich performance present in comparisson the original? Hummm! Here is the problem. I used the original detector and the only big problem I found with it is the bad performance in terrain extremely wet... This detector is very sensitive. I remember I found with it copper mineral, green mineral.

[WM6]

Originally Posted by ivconic

. For example; i would like to know how they calculated coupling relation between Al loop and small coil inside it? What relation? What is resonance of Al loop? What happening if loop was with different sizes? What are merrits and what drawbacks from such coupling. Is loop size dependable on working frequency and how? How possibly that loop can be suitable for such low frequency? Is it the coupled coil the one which solving that issue?

What do you mean by "Al loop and small coil inside it"? Maybe schematic is some unclear regarding coils, but Al loop are not inductive coupled to "small coil" but electric connected by wire in one only coil. "Small coil" are secondary winding inside ferite potcore and form togheter with Al loop one coil which resonate down harmonic to primary (tunable) LC tank. So loop and "small coil" byself resonate out of TR frequency and are by this only slightly coupled which cause by near target escape from balanced (tuned) nulling at given resonance and by this tone in RX (like by un-nulled device).

[ivconic]

Originally Posted by WM6

What do you mean by "Al loop and small coil inside it"? Maybe schematic is some unclear regarding coils, but Al loop are not inductive coupled to "small coil" but electric connected by wire in one only coil. "Small coil" are secondary winding inside ferite potcore and form togheter with Al loop one coil which resonate down harmonic to primary (tunable) LC tank. So loop and "small coil" byself resonate out of TR frequency and are by this only slightly coupled which cause by near target escape from balanced (tuned) nulling at given resonance and by this tone in RX (like by un-nulled device).

Is that was the case!? I mixed it up than! Had also another project on my mind. Never mind, my question is still there, only preformulated. Calculations..i am interesting to see what calculations were used there..

[ivconic]

Since my memory is not serving me well lately i just checked at :

http://www.geotech1.com/forums/showt...ighlight=tm808

and yes, that's what i ment, although i formulated it wrong.
Al loop is connected with primary winding and IT IS COUPLED with secondary winding.
You are right and i am right also. Only i missed to say that loop is a part of primary coil...
So...i will preformulate again question; what are calculations for relation between loop dimensions and primary coil? And all that in relation to secondary coil? How to calculate best relation?
For example; i would want to make loop with much different dimensions, so i must correct primary and secondary coils also, right?

[WM6]

[quote=ivconic;106244]Since my memory is not serving me well lately i just checked at :

http://www.geotech1.com/forums/showt...ighlight=tm808


Sorry, I am not discuss TM808, I discuss "Deep seeking metal locator" by Phil Wait and Roger Harrison you mentioned in post #25. I do not remember TM 808 schematic, I was never interested in it.

[ivconic]

Sorry, I am not discuss TM808, I discuss "Deep seeking metal locator" by Phil Wait and Roger Harrison you mentioned in post #25. I do not remember TM 808 schematic, I was never interested in it.

Never mind actually. Principles should be the same.