best reviews metal detectors for gold
Interesting information about treasure hunters
The simplest metal detector
The MD receiver scheme is the second option

Metal detector options

The working frequency is about 2 kHz.

The depth of the coin with a diameter of 25 mm - 9 cm;

The iron roll cover from the jar is 25 cm;

Is an aluminium sheet measuring 200 to 300 mm - 45 cm;

60 cm sewer hatch.

Connected search coils should be absolutely single in size and winding date. They should be arranged so that in the absence of foreign metal objects communication between them is practically absent, examples of coils are shown.
If the reel of the transmitter and receiver is positioned in this way, the signal of the transmitter in the receiver will not be listened to. When there is a metal object near this balanced system, so-called vortex currents appear in it under the influence of a variable magnetic field of the transmitting coil and, as a result, its own magnetic field, which leads to the receiving coil variable EDS.

The signal received by the receiver is converted by the phones into sound. The metal detector scheme is really very simple, but despite this, it works pretty well, and the sensitivity is not bad. The multi-vibrator of the transmitting unit can be assembled on other transistors of a similar structure.

The metal detector coils are 200x100mm in size and contain about 80 wire twists of 0.6-0.8mm. To check the transmitter, instead of an L1 coil, the headphones are plugged in and make sure that when the power is turned on, the sound is heard. Then, by plugging the coil into place, they control the current consumed by the transmitter - 5. 8 mA.

About the company
The receiver is set up at a closed entrance. The R1 resistor selection in the first cascade and R3 in the second set the voltage on the collectors respectively, equal to about half of the voltage of the power. Then, the R5 resistor is siper to ensure that the current of the VT3 transistor collector is equal to 5. 8 mA. After that, unlocking the entrance, connect to it coil receiver L1 and, taking the signal of the transmitter at a distance of about 1 m, make sure that the device is healthy.