mono coil IB

[Tinkerer]

Correct, the compensation is on the RX. I will post the circuit with white background.

With the compensation on the TX, using a bucking coil, the coil field is less uniform and therefore has less depth penetration.

Compensating on the RX side leaves a cleaner TC magnetic field.

This compensation coil can be placed anywhere and of any amount of turns/inductance. The electronic compensation network does the adjustment and balancing.

[mickstv]

Yeah I had the same problems when I was working on the TEM and trying to compensate on the TX side.

I might try the RX side compensation. Set it up with manual control first, then try to work out an automatic control.

[Tinkerer]

Preamp with Flyback compensation

Here is the complete preamp circuit to the ADC

[mickstv]

Here is the complete preamp circuit to the ADC

Thanks Tinkerer.

[Tinkerer]

Yeah I had the same problems when I was working on the TEM and trying to compensate on the TX side.

I might try the RX side compensation. Set it up with manual control first, then try to work out an automatic control.

If you feel like experimenting, we could use a modified TEM TX, (continuous current, non reactive sample time)

[mickstv]

If you feel like experimenting, we could use a modified TEM TX, (continuous current, non reactive sample time)

I might as well, but I'll have to find up the TEM circuit I built first. To you have a circuit for the modified TEM TX ?

[Tinkerer]

I might as well, but I'll have to find up the TEM circuit I built first. To you have a circuit for the modified TEM TX ?

I will look for it.

I also have a few first run PCB's (not populated) of the RX as shown below. Note that there were some mistakes but fixed. Let me know if you want one.

[mickstv]

I will look for it.

I also have a few first run PCB's (not populated) of the RX as shown below. Note that there were some mistakes but fixed. Let me know if you want one.

Once I get the TX circuit from you and if I get it working correctly, I might buy a RX board.

Thanks Tinkerer.

[Tinkerer]

Once I get the TX circuit from you and if I get it working correctly, I might buy a RX board.

Thanks Tinkerer.

I am not selling any PCB. I am offering to give you a PCB for FREE.

[mickstv]

I am not selling any PCB. I am offering to give you a PCB for FREE.

Thanks for the offer Tinkerer.

Although I'll still see how I go with the TX first. Have you been able to find the schematic for the TX section yet ?

[sinclairuser]

hi all, been reading this and other searched threads, as i still haven't found a coil design that suits my project.
i'm putting a vlf and pi in the same enclosure, for specific tasks, the coil design is where it get troublesome.
i dont care what design i use either as long as it fits in one coil shell, my first idea was to use a foster type pi with high inductance, build the coil ib style, use a vlf that had specs near to the coil then tune the vlf to the coil.
allthough the rough breadboard worked, the pi did not like having the unpowered vlf connected to its coil, so i am now dual switching the two detectors, pi on vlf off and vice versa, both+ and - simultaneously, diodes/caps protect the vlf from the pi circuit at the coil.
its very early days but both boards detect metal and dont detect each other, but its very complex, crude and far from ideal.
so something like a single loop ib coil may help here.
thanks,
aly.

[Tinkerer]

Coil matching circuit

This is a circuit that matches the input of the signal coil that has 316uH inductance
and the compensation coil that has 15uH inductance.

Both coils pick up the TX voltage pulse of 300V, in opposite phase.

The 2 signals are matched and nulled.

Only a very small residual TX signal is left, but the target signal remains and is then amplified.

This circuit does the job, but it could be much simplified and improved.

Any suggestions?