Analog Demodulator Stability Problem

[Carl-NC]

The resistive channel (R) is actually the quadrature channel (Q) and is used for the all-metal signal. Normally you want to use a ground-balanced version of the R channel, what I call the G channel. That way the AM signal is immune to ground. The disc signal uses both X & R, as Altra says.

[pito]

sometimes they use Ux and Uy

[Daves]

The resistive channel (R) is actually the quadrature channel (Q) and is used for the all-metal signal. Normally you want to use a ground-balanced version of the R channel, what I call the G channel. That way the AM signal is immune to ground. The disc signal uses both X & R, as Altra says.

Carl, I have a firebrick that responds like ferrite, close to ferrite.
I tried putting coin on the brick in the left, middle and right corner.
I tried sticking coin under the brick in the left, middle and right corners.
Note: I have the brick in hand, doing an air test. It's not underground.

Would you look at the id differences between All Metal and Disc modes? What is the reason of this? How can disc mode give such a stable id? Are there different filters used?
Note: The device I tried works as direct sampling. It takes the TX clock from the TX driver and transmits it to the ADC and the data goes to the processor. There is no analog demodulator.

All Metal (Target=Coin)

Coin on Brick, Right Side: 75,34,77,38,73,47,74,45
Coin on Brick, Center: 48,49,46,36,48,46
Coin on Brick, Left Side: 35,74,31,76,28

Coin under Brick, Right Side:70,57,70,56,70,56
Coin under Brick, Center: 56,61,57,61,58,62
Coin under Brick, Left Side: 57,71,56,70,56,71

Discrim (Target=Coin)

Coin on Brick Right Side: 70,66,69,65,61
Coin on Brick, Center: 55,49,56
Coin on Brick, Left Side: 67,65,66,63,64

Coin under Brick, Right Side: 65,66
Coin under Brick, Center: 63,61,62
Coin under Brick, Left Side: 65,66

[Carl-NC]

Without access to the code I can't say what is going on. Typically Disc mode uses 2nd derivative signals while AM is 1st derivative or maybe even static.

[Daves]

Without access to the code I can't say what is going on. Typically Disc mode uses 2nd derivative signals while AM is 1st derivative or maybe even static.

Carl, I tried using the 2nd derivative and the 1st derivative, but I could not see any difference in obtaining the target id. I can't understand the difference in the id list I wrote above.

[moodz]

This discussion is like giving someone a watch or someother complex mechanism and asking them how it works but without taking it apart / opening it to see how it actually works ....

The other consideration is the a priori knowledge that there is a coin under the brick .... try a double blind test. Have someone else put random or no target under random bricks or no brick where you cant see either brick or coin and then analyse the results.
Because in real search ... you cant see em.