Detector with ferrite core coils

[lucifer]

Article translated from Bulgarian magazine published in 1972.

[detectoman]

ok very interst i need coils specifications and wires cal, conversion of components momenclatures to occidental denominations, and other details if exist, thanks
this cores configuration, is very extrange for me

[lucifer]

There aren't any more explanations and details in original article. But Gervm mentioned Russian and US models using the same principle. I hope to upload them soon.

[ApBerg]

Hello Lucifer.

Thanks for the info !

Best regards.

Ap

[mikebg]

Lucifer,
This is the circuit diagram of Bulgarian mine locator model MT60 or MT62. It is designed by Bulgarian engineers in 1960 or 1962 and made of Bulgarian transistors produced under license from a French company. This article contains false information and was written incorrectly too. It is not done properly and not explained correct the block diagram in Fig. 1. There are many errors in the circuit diagram Fig. 2 and coils data. Each bias resistor (connected with its lower lead to base of a transistor), should be connected with its upper lead to respective collector. For example the upper lead of resistor R8 is connected to lower lead of resistor R7. Resistor R4 and capacitor 2uF are used for amplitude modulation. There is hardly a normal designer in the world to use in a design two potentiometers so different in value as 25K and 26K!
For selectivity are used two tuned tanks formed by Tp1 and Tp2. These are transformers for pocket radio with steel core, adjusted with capacitors to resonate at TX frequency.

[Geo]

Hi Mikebg.
Can you post the original schematic????

[mikebg]

TWIN LOOP with ferrite and metal cores

Detectorman, this configuration is incompetent design of sensor type TWIN LOOP, because the excitation with TX coil is in two opposite directions. Therefore, sensors can not suppress the signal from the ground and interference from distant sources. Besides three ferrite cores, there are two metal cores in sensor, which adjust fine induction balance.

The shown in article design was made by radio amateurs in 1967 when they were soldiers in the army and had parts available for this mine locator. After having finished their military service, they are spread the circuit diagram of mine locator among Bulgarian ham radio designers.
They perfected that sensors instead of 3 ferrite rods are used 2 pieces П-shaped ferite cores for transformer from horizontal deviation of the TV (because they have not found a suitable E-shaped ferrite core). Instead fine adjustment with metal cores, amateurs tune induction balance by shifting one turn of RX coil. In the folded position, the modernized mashine has size 4 x 12 x 40cm.
Sensors with ferrite cores have the following advantages:
1. Small size. That matters for military mine locator.
2. High Q-factor of the tuned tanks. To create a narrow band metal detector, it is also important. However this machine is broadband because TX is not CW, but amplitude modulated with sound frequency.
3. The timeconstant of ground signal is small because TX coil has a small diameter.
If the design is of interest for you or for someone from this forum, let announce this. We can put the task of the REMI group to make drawings and photographs of the original and of improved by amateurs version, and to write new article without errors. However, this happens only at the beginning of 2010. :-(

[Gervm]

I think it is not nesessery for anybody make the same detector but if you take idea then change transistor amplifire with one OPAMP add active filter on another OPAMP and you`ll get very simple, litle and light device for biginers that can find a coin at depth 15 sm or deeper. And now look at this fabrik head. Are there many differenses whith bulgarian?

[mikebg]

Geo, this will happen in January. For now I can make correction of published block and circuit diagrams only according my own shabby memory.
Gervm, the Bulgarian sensor has 3 ferrite rods and 4 cores for adjustment. Both RX coils are on vertical rods. This is russian design with only one horizontal TX rod and only two different cores (ferrite and bronze).

[Gervm]

I say about idea you can realise it more perfecly or less but it is good food for mind. May be somebody find more effective orientation of TX and RX coils and technological solutions. It is not interesting to make the same. Your result must be better.

[detectoman]

thanks to your mikebg, and gervm, i aprecciate very much you attention for me, may be one modified actual circuit of this, can build one functional good detector, semms fine and powerfull machine, embrace for my brothers

[detectoman]

i have interest on these detector, please mikebg have you any other details? yes i await to january

[mikebg]

Sensor for BG mine locator MT62

Sensor for BG mine locator MT62
1. TX coil winding - 1 off
2. Ferrite rod short (for RX) - 2 off
3. RX coil winding - 2 off
4. Ferrite rod long (for TX) - 1 off
5. Ferrite core - 2 off
6. Bronze core - 2 off

[mikebg]

Amateur sensor for schematic MT62

Amateur sensor for schematic MT62
1. RX bobbin - 2 off
2. TX bobbin - 2 off
3. Capacitors type MKP (for TX) - 2 off
4. Ferrite core type П - 2 off

[mikebg]

Wiring

Wiring inside ferrite sensing head (amateur variant).
All bobbins are winded in the same direction.