THE ELUSVE 1us TC TARGET

[Tinkerer]

This solution reduced hand's influence on the connecting cable but not absolutely

It needs the right cable. I dont know of any better way than "trial and error" to chose the right cable. I must have tried 100 different cables, including many cables I assembled myself.

[Tinkerer]

When two "guru" members dialogue, the practice have to be the true of last instance! The practice show that the perimeter of the target gives the strength of the received signal in PI system.

You mean the surface area. Correct, if the area is reasonably flat.

[Detectorist#1]

This solution reduced hand's influence on the connecting cable but not absolutely

[Detectorist#1]

I continue to work on this problem. Now, I check the results with using of separate Tx end stage and first Rx stage on one small board inside searching head.

[Detectorist#1]

But both of you are right- the type of the cable and right connection to the MD's box is very important especially in fast PI.

[Detectorist#1]

When two "guru" members dialogue, the practice have to be the true of last instance! The practice show that the perimeter of the target gives the strength of the received signal in PI system.

[pito]

you have a problem with shield not me.

[Tinkerer]

calculations, simulations are not the same in real world, have you measured the shield to grounding capacitance ?

check the AMX coil thread

[pito]

calculations, simulations are not the same in real world, have you measured the shield to grounding capacitance ?

[Tinkerer]

then how come you have = High current in the cable induces a (relatively) high current in the shield. = ???
follow post #70, I am not want to guessing any more.

capacitane/inductance calculations (mogami.com)
The mogami inductance calculator can give you an idea about inductance in cables. The Mogami cables are of the best in the world.

AC resistance of parallel conductors (mogami.com)

[Tinkerer]

[ATTACH]n419523[/ATTACH] Here is the last breadboard experiment of the preamp. with a gain of 15x47. The black trace on the scope shows the signal of a 25x25mm kitchen foil. I will now starting to draw the layout of the Preamp PCB. I will also end this thread and continue on the AMX RX thread where is belongs. https://www.geotech1.com/forums/foru.../408950-amx-rx

[pito]

then how come you have = High current in the cable induces a (relatively) high current in the shield. = ???
follow post #70, I am not want to guessing any more.

[Tinkerer]

my guess (based on info you provided) , you are using 2 wire audio cable with the shield, for Rx one wire and ground for Tx second wire and ground,
You are offering a circuit for a VLF detector = for any balancing

The coil cable is composed of 4 wires + shield. 2 wires for TX, 2 wires for RX, the shield of the coil is connected to the shield of the cable. Cheap cable from ailiexpess.
I als bought a similar cable with 5 wires, in case I want to try with a center tapped RX.

[pito]

Yes, it is a single frequency compensator, over 95% compensation for sine wave, for pulse I think it will be about 80%.

[Carl-NC]

You are offering a circuit for a VLF detector = for any balancing

The nulling circuit in post #63 will only work for a narrowband single frequency. Won't work for MF or pulse.