2 boxxxx :)

[Thomas]

Yes, that would be much better, easy to find 7555. I would try 2n5401 for 3906.

[Geo]

Detectors of the transmitter-receiver with a frequency above 20 kHz work well only in the beach.In the ground work well at frequencies below 18 kHz.

Before 30 years with the same 2box locator i located a metalic box about 20x30x10cm at depth 2m at a mountain.

[totob]

Finally I finished building (Re-make of the Treasure Witcher by Charles Drake),
but it is sensitive only to very large metal at least 30/20 cm at distance 20 cm.
Also I noted that the reciever battery decharging fast which leade to weakening of the power of reciever.
I hope any one can fix theseproblems through below pictures.

transmitter

[IMG][/IMG]

reciever

[IMG][/IMG]


[IMG][/IMG]

coils

[IMG][/IMG]

Final form

[IMG][/IMG]

[smity]

Totob, you sensors balanced? If so, how?

[mikebg]

Totob, you sensors balanced? If so, how?

Induction balanced or weight balanced?

[smity]

It seems that there are balanced in weight.: LOL: Why "receiver coil" you are right angles? Why are not parallel? And how do you balance in "0"?

[Qiaozhi]

Totob, you sensors balanced? If so, how?

For use in the field, the right-hand coil is moved so that it is parallel to the ground. I think it's only in that position to keep it steady for the photo.

[Geo]

Problems.......
1.Coils must be vertical between them.
2. Distance between coils must be at least 80...90 cm if you are looking for objects with dimentions as a soda can or larger.
3. It is good to place the oscilator near to Tx coil and the receiver near to Rx coil. Every pcb must have its own battery

[totob]

Totob, you sensors balanced? If so, how?

Yes the reciever coil in the right angle, at this position i hear very low tone (balance in 0).
Also when it is in the horizontal position to the ground the balance in 0.
so the two positions is ok

[totob]

Problems.......
1.Coils must be vertical between them.
2. Distance between coils must be at least 80...90 cm if you are looking for objects with dimentions as a soda can or larger.
3. It is good to place the oscilator near to Tx coil and the receiver near to Rx coil. Every pcb must have its own battery

I don't get a tone at distance 80cm, only at maximum 60 cm when the battery of transmitter is fully charged.
After few moment of working the power of transmitter becomes weak, that's leading to shortage distance necessary between coils, (30 to 40 cm).
note: when i cheked the 9v battery of transmitter i find it 6.5v

3. It is good to place the oscilator near to Tx coil and the receiver near to Rx coil. Every pcb must have its own battery: I don't understand this

[Davor]

IMHO it could be possible to turn any half way decent VLF into a real passive two box Rx with discrimination and all. Guess someone else already did that, but it is my 2 cents anyway.
In the odd case that this does not exist I know the exact way to do that.

[damyzo]

Great job Guru. Does it work and do you build it at home. I want to build this metal detector But i want to be sure that is correct. Thanks !!!

[totob]

Problems.......
1.Coils must be vertical between them.
2. Distance between coils must be at least 80...90 cm if you are looking for objects with dimentions as a soda can or larger.
3. It is good to place the oscilator near to Tx coil and the receiver near to Rx coil. Every pcb must have its own battery

I don't get a tone at distance 80cm, only at maximum 60 cm when the battery of transmitter is fully charged.
After few moment of working the power of transmitter becomes weak, that's leading to shortage distance necessary between coils, (30 to 40 cm).
note: when i cheked the 9v battery of transmitter i find it 6.5v

3. It is good to place the oscilator near to Tx coil and the receiver near to Rx coil. Every pcb must have its own battery: I don't understand this

[ODM]

I don't understand this

It means to build the transmitter and receiver circuits as separate from each other, powered with separate batteries, to isolate them from each other.

[chemelec]

note: when i cheked the 9v battery of transmitter i find it 6.5v

The Transmitter Draws considerable Current.
Just a Small 9 Volt Battery is Not very good.
You need a Higher Amperage Battery.