IN 1980-81 (B & W PHOTO)

[Geo]

Before emit the BFO an only hertz, the amplification enlarge this "soft breeze". With this type of detector (I had one of 80's generation) I found a copper plate 120 X 60 cm (very big) at 50 meter distance and 1.5 meter depth with a coil of 11-12 cm diameter.

The old coil I saw was turn by turn, but other models has classic winding. The BFO is a transmitter since is an oscillator and at the same time is a receiver, so attention with the "obsolete".

Here exactly the middle and the end of 80's pistol I had:

Hi Esteban.
Perhaps if it published the schematic of this 80's detector in forum it was found guys that would make good and intelligent modifications so that it becomes enough better . You do not know some time what becomes
Regards

[gold24h]

frequency

I would like to build one of these,what frequency does the transmitter transmit and the receiver receive?

[okantex]

hi

Hi Estebanif this pistol detector is a kind of BFO
where is the reference oscilator coil?
and why why there is a antenna in radio part.
and does it work when it is turned to ground(what we do when pinpointing with mineoro)I wonder its dept penetration in this position.

[Esteban]

Hi, the reference coil is in the black head.

In the radio is the called "classifier".

[okantex]

Excuse me ,I am just tryiing to learn about electronics you know.
if refrence osc. in black )also beat osc must be in bleck because it is the one we use in bfo),so what is the antenna for in radio ?
clasifer must get signal from beat osc. ,if not what is the cable for between black and clasifier?

[Esteban]

Search coil is the front, the circuit is in the black head, include the fix oscillator with his coil. The zero is make with precise tandem. This circuit is linked to the aluminium box with the shielded cable, in where is the radio and classifier control with potentiometer.

Variations there are severals, but the principle is equal in the major part.

[gold24h]

Can anybody explain how this works,does it resonate the buried metel.The black part must be a transmitter,it is possible to transmitt a signal in the air at say two watts power and receive the signal at a mile or more for mhz frequency range,but how could the signal go from the air then enter the ground where the metel is and cause it to resonate.If the metel was truly resonating you could receive the resonated signal from a mile away with a good receiver.