Ideas to tinker

[Tinkerer]

I'm wondering about EFE and GB also. Maybe TEM is better if the coil is stationary, detecting moving targets?

I tried to apply the method to stationary systems, like "Ground Loop", where a large TX coil is laid on the ground and then one walks within that loop with the RX coil. Tried this with a loop of 20 meter diameter. Run into the problem that the field strength within the TX loop is not uniform. I varies between the center and the rim.

Trying to layout 10 sample window signal paths in analog finally got so complicated that I searched for a digital solution.
Could not find any help for DSP. DSP needed real programming skill, whereas I just barely managed to setup a sequential timing schedule for an 8bit PIC.

Tried several other methods, more about that later.

[green]

I would like to see how the EFE field is controlled, or the GB, but I already asked many questions. Thanks again.

I'm wondering about EFE and GB also. Maybe TEM is better if the coil is stationary, detecting moving targets?

[Tinkerer]

Are you looking at right side circuit?

This one is right. the one before had a 1420 Ohm damping resistor.

[Jose]

TEM. reminds me of horizontal TV output with TRC.
I have seen some TVs, which worked with the horizontal output transistor without heat sink.
I also remember that they had efficiency diodes in parallel, the horizontal frequency was 15625 Hz and the pulse width was 64 us. just to get an idea of how often it can operate.

[green]

Interesting experiment.

This is not TEM. TEM recycles the Flyback power. This makes it more power efficient than traditional PI.
The side effect is that it becomes more VLF like. I have run it with up to 15 Amps peak current, (real circuit, real 6ft diameter coil, #10AWG wire) at high repetition rate, while consuming a fraction of what a traditional PI would consume.

Are you looking at right side circuit?

[Tinkerer]

Thanks Tinkerer, it looks clearer now and the use of a balanced coil is justified.
As Eclipse says, the TX width must keep a certain relationship with the frequency, so that it does not oscillate, I think of a relatively higher frequency than traditional PIs.
I would like to see how the EFE field is controlled, or the GB, but I already asked many questions. Thanks again.

I used to take 5 to 10 sample windows, then add or subtract the windows among each other.

The 0 crossing is the important spot in time. Before the 0 crossing, you see the decay of the targets.
After the 0 crossing, you see the "target charge".

The full interaction of the magnetic pulse with the target during the whole cycle is complex and I don't know how to explain it.

Maybe if somebody who is good at drawing could try to put my explanation into graphics it could become understandable.

Of course it could be explained with mathematics. We can see that LTSpice calculates perfectly what is happening. Unfortunately this is way beyond my capability.

[Tinkerer]

Changed 24in_DD normal PI to what I think is TEM? Looks good.

Interesting experiment.

This is not TEM. TEM recycles the Flyback power. This makes it more power efficient than traditional PI.
The side effect is that it becomes more VLF like. I have run it with up to 15 Amps peak current, (real circuit, real 6ft diameter coil, #10AWG wire) at high repetition rate, while consuming a fraction of what a traditional PI would consume.

[green]

Changed 24in_DD normal PI to what I think is TEM? Looks good.

[green]

Added Rx coil to simulation. Looks like it would be worth trying with real circuit.

[Tinkerer]

Normal PI looks at R signal. Ground from my back yard and ground from California cancel with the same sample settings. They don't if I look at the X signal(when Tx current is changing). How does the TEM cancel ground? Is it looking at the X signal or am I missing something?

You are right.
In this sense it is like a VLF, TX current is always ON and changing. VLF demodulation looks at the 0 crossing.

[Jose]

Thanks Tinkerer, it looks clearer now and the use of a balanced coil is justified.
As Eclipse says, the TX width must keep a certain relationship with the frequency, so that it does not oscillate, I think of a relatively higher frequency than traditional PIs.
I would like to see how the EFE field is controlled, or the GB, but I already asked many questions. Thanks again.

[green]

Normal PI looks at R signal. Ground from my back yard and ground from California cancel with the same sample settings. They don't if I look at the X signal(when Tx current is changing). How does the TEM cancel ground? Is it looking at the X signal or am I missing something?

[eclipse]

Excellent.

On the TINKERER-TEM, the decay goes to about 0, but does not stay, it crosses over. So your 0 is the crossover point.

The crossover point can be manipulated. If the TX cycle is too long the coil starts ringing soon after reaching 0.
But if you increase the frequency the ringing time overlaps with the next TX cycle.

[Tinkerer]

The first image shows the response of both methods to target 50 us.
In the second image, the target response 50 us and current in the coil in the TEM method.
It was also observed that at the moment the target signal is reaching zero, the current in the coil is increasing.[ATTACH]50935[/ATTACH][ATTACH]50936[/ATTACH]

Excellent.
You can see that the traditional PI decay curve goes to about 0 and stays there until the next TX pulse.
On the TINKERER-TEM, the decay goes to about 0, but does not stay, it crosses over. So your 0 is the crossover point.
For the TINKERER-TEM you need a separate RX coil. You can use an IB or Induction Balance setup like a DD coil, or a concentric RX coil. There are several variations.

[Jose]

The first image shows the response of both methods to target 50 us.
In the second image, the target response 50 us and current in the coil in the TEM method.
It was also observed that at the moment the target signal is reaching zero, the current in the coil is increasing.