My design and its depressing resoults

[Pep_T]

I spotted now one unintentional mistake on schematic.
D15 cathode goes ONLY to D1 anode.
There is an excess, a point connecting the D15 cathode also to the D16 cathode and D2 anode.
That connection does not exist. Otherwise, you will hear the same sound in both channels.
It is one of many schematic revisions. But it is the final.
Somewhere in the process of revising from revision to revision; it just happened that that connection point was added unintentionally.
Otherwise, there is no such error on the pcb that I published then.
Ignore that connection and you can completely omit D15 and D16.
Two lines going from the 4024 to two separate audio outputs; they must be separated and not joined.

Found it, nothing terrible, thank you for bringing that up!

[Carl-NC]

3rd ed is still under construction. I don't have a release date, but it may push into 2024.

[Pep_T]

Hi, what do you suggest me to do? If the 3rd edition will be out in less than a year I do not think it will be a problem to wait. Who better than you to advice me

[Qiaozhi]

Hi, you should be Mr. Overton, right? My pleasure. Is the edition you mentioned freely available? I do not see anything in the firs link except for the ISBN of the book. If not I will wait for the 3rd edition that, as I read, should be published shortly, right? I am looking forward to buy it whenever it gets out.

ITMD is available from Amazon.
Here's a link to the UK site -> https://www.amazon.co.uk/Inside-Meta...7619541&sr=1-1

[Pep_T]

I spotted now one unintentional mistake on schematic.
D15 cathode goes ONLY to D1 anode.
There is an excess, a point connecting the D15 cathode also to the D16 cathode and D2 anode.
That connection does not exist. Otherwise, you will hear the same sound in both channels.
It is one of many schematic revisions. But it is the final.
Somewhere in the process of revising from revision to revision; it just happened that that connection point was added unintentionally.
Otherwise, there is no such error on the pcb that I published then.
Ignore that connection and you can completely omit D15 and D16.
Two lines going from the 4024 to two separate audio outputs; they must be separated and not joined.

I might have spotted another possible mistake: U7B and U7D inputs are flipped. Since U7A and U7C are not flipped and the two part of the schematic are complemetary, I suspect neither U7B and U7D should be.
But again this are pure speculation based on the simmetry of the 2 circuit section.

[Skippy]

Quote:"I am starting with an IB detector. Here's what I did so far:
1. TX coil: 2. RX coil: 180 turns, 0.35mm wire diameter. Coil diameter is 22cm, L = 4.6mH. Shielded with aluminum foil connected to GND.
No-one has picked up on this error: Al is way too conductive, and will kill sensitivity. Graphite paint is the preferred shield - conductive, but not excessively so. There are other alternatives, like metallised mylar sheet, or woven cupro-nickel fabric, but graphite is the simplest. Alternatively, you can use a long narrow strip of paper. Apply adhesive tape ( Scotch tape, Sellotape ) to one side, for strength, and coat the other side heavily with pencil lead from a 6B artists pencil. Then spiral wrap the paper around the coil. Make a mechanical connection to a thin piece of tinned copper wire, to join to ground.

[ivconic]

Quote:"I am starting with an IB detector. Here's what I did so far:
1. TX coil: 2. RX coil: 180 turns, 0.35mm wire diameter. Coil diameter is 22cm, L = 4.6mH. Shielded with aluminum foil connected to GND.
No-one has picked up on this error: Al is way too conductive, and will kill sensitivity. Graphite paint is the preferred shield - conductive, but not excessively so. There are other alternatives, like metallised mylar sheet, or woven cupro-nickel fabric, but graphite is the simplest. Alternatively, you can use a long narrow strip of paper. Apply adhesive tape ( Scotch tape, Sellotape ) to one side, for strength, and coat the other side heavily with pencil lead from a 6B artists pencil. Then spiral wrap the paper around the coil. Make a mechanical connection to a thin piece of tinned copper wire, to join to ground.

I kinda disagree.
I made 200 probably tens more than 200 coils so far.
EACH one shielded with thin adhesive Al foil.
TGSL is not that deep alright, but GEB&DISC works 100% ACCURATE.
White's Classic III copies, numerous, all working deep.
Wave, Golden Mask IV copy... very deep.
But SMW...! Deepest VLF ever!
So... in practice Al foil is not problem at all.
Your opinion might be relevant only in case of use of some thick "kitchen" foil,
I can't tell, I always used extra thin self adhesive Al tape.

[ivconic]

I might have spotted another possible mistake: U7B and U7D inputs are flipped. Since U7A and U7C are not flipped and the two part of the schematic are complemetary, I suspect neither U7B and U7D should be.
But again this are pure speculation based on the simmetry of the 2 circuit section.

Both ways you'll get workable detector.
If you followed the topic from the start (can't blame you, it is huge with lot of irrelevant posts); you'll know that later Davor appeared with his indeed good modifications.
I suggest you to find the page where Davor gave his modified version. It seems to me his version is quite better.

[Pep_T]

Both ways you'll get workable detector.
If you followed the topic from the start (can't blame you, it is huge with lot of irrelevant posts); you'll know that later Davor appeared with his indeed good modifications.
I suggest you to find the page where Davor gave his modified version. It seems to me his version is quite better.

[....]

Your opinion might be relevant only in case of use of some thick "kitchen" foil

Yeah, thats on me, did not read it complitely but I promised myself I will. Thanks.

To be honest, I am using some kitchen alluminum foil, but is extrimely thin, It was really difficult to wrap it around the coil and not tear it down. It is held down by a non isulated copper wire, but the wire is not thin, 0.8mm diameter to give the coil some strenght

[Skippy]

Did you leave a small (1mm - 5mm ) gap in the foil, so there is not a complete loop of foil ? This is very important, the difference is massive.

[ivconic]

Yeah, thats on me, did not read it complitely but I promised myself I will. Thanks.

To be honest, I am using some kitchen alluminum foil, but is extrimely thin, It was really difficult to wrap it around the coil and not tear it down. It is held down by a non isulated copper wire, but the wire is not thin, 0.8mm diameter to give the coil some strenght

I guess there is self adhesive Al tape in local shops?
Here I can buy Al foil but also Cu foil, both self adhesive and thin.
Haven't tried with Cu foil yet, haven't made coil for long time now.
Ever since I switched to stock coils to use with my diys.
...
Randomly I search Aliexpress and day by day their offer is richer and richer.
There are good coils by very affordable prices!
For example; you can buy separate Garrett Ace coil from there.
I had few of those in the recent past, 100% good copy of Garret Ace, working exactly the same.
Same with X-Terra copies, Fisher Gold Bug Pro copies too.
I had those Chinese copies and tested them, I have no remarks at all.
Here are some links:

1) Fisher Gold Bug Pro copy: https://www.aliexpress.com/item/1005...d=kDZa3DF3UfNI
2) Another Fisher Gold Bug Pro copy: https://www.aliexpress.com/item/3261...d=4mDa791qdDRA
3) Garrett Ace copy: https://www.aliexpress.com/item/1005...d=an3KyDzV0HHB
4) Minelab X-Terra copy: https://www.aliexpress.com/item/1005...d=lOGDtgksrBcw
5) Can't recognize this one, but looks promising: https://www.aliexpress.com/item/3285...d=c2uhtS9oOHlB
6) This one is probably poor design, but price is fantastic, shaft, coil, enclosure... total pay off: https://www.aliexpress.com/item/3283...d=lXPjIkW8parU

[ivconic]

Separate coils:
1) https://www.aliexpress.com/item/1005...d=Sf6tMGKNBZUG
2) https://www.aliexpress.com/item/1005...d=0ZV7wsgzGdS5
3) https://www.aliexpress.com/item/1005...d=6ZPUUz8iW6rI
4) https://www.aliexpress.com/item/4001...d=Y8Et13NM34ck
...
and so on...
You see my point?
Why torturing and making diy coils today?

[Olly]

Separate coils:
1) https://www.aliexpress.com/item/1005...d=Sf6tMGKNBZUG
2) https://www.aliexpress.com/item/1005...d=0ZV7wsgzGdS5
3) https://www.aliexpress.com/item/1005...d=6ZPUUz8iW6rI
4) https://www.aliexpress.com/item/4001...d=Y8Et13NM34ck
...
and so on...
You see my point?
Why torturing and making diy coils today?

I see your point, that's an awful lot of headaches and time saved isn't it?

Have you used any of these with a TGSL, or what would you suggest from Aliexpress as a good match for the TGSL?

[ivconic]

I see your point, that's an awful lot of headaches and time saved isn't it?

Have you used any of these with a TGSL, or what would you suggest from Aliexpress as a good match for the TGSL?

For TGSL... tough! Bad luck!
Tesoro coils from older series are simply "awkward" for finding the stock replacement.
I have no clue, honestly speaking.
Coil for Fisher Gold Bug Pro is what I used several times.
Inuctances and resistances are just sweet for adapting in diys.
But unfortunatelly not for Tesoro based diys.



P.S.
Coil for Fisher Gold Bug Pro:
TX = 0.87mH, 0.846mH, 0.85mH...... 33 to 42 ohms
RX = 8.7mH, 8.12mH, 8.61mH, 9mH... 1.8 to 2.9ohms

[Pep_T]

Did you leave a small (1mm - 5mm ) gap in the foil, so there is not a complete loop of foil ? This is very important, the difference is massive.

Yep, 1cm gap and no ground loop.

I am really considering buying a MD head (thanks for the link! I did not know I could have found them for this cheap!) and concentrate on the electronics. I'll keep you posted and in the meantime I will continue the reading on the TGSL conversation.