After zeroing, the search depth became worse!?

[Ravensouth]

I tried to zero the coils again and got the following values: A) Directly at the RX coil I reached 0,000V AC according to the multimeter. B) At the pin 5 of the LM358 I also reached a 0V DC voltage. C) At the pin7 of the Lf353 I have about 200mV ... is that too much? Strangely enough, I did not achieve these best values until after removing the GND from the RX (-). Now I send only mass over the TX (-).

[Ravensouth]

On Monday, I'll try again to measure these results with the oscilloscope. But these results are not 100% perfect, right? I was able to eject the ferrite with the ground poti. Then I tried the 1 euro coin. I only got a depth of 24-27cm in the disc on High Sens. All Metal mode did not work because there were too many glitches in the room

[ivconic]

On Monday, I'll try again to measure these results with the oscilloscope. But these results are not 100% perfect, right? I was able to eject the ferrite with the ground poti. Then I tried the 1 euro coin. I only got a depth of 24-27cm in the disc on High Sens. All Metal mode did not work because there were too many glitches in the room

I think you got optimum with that coil.
As you noted: "...My inductance was 5.4mH at Tx and 5.8-5.9mH at Rx..."
Well...
I would suggest you to make another coil, this time TX~5.7mH and RX~6.2mH, both with 0.25mm.
Also look at this sketch; that's the way how i wired my coils, all of them:

[ivconic]

RX lead that goes to inverting input of LF353; goes to common GND, but down there in coil only, not up there in detector's housing and on pcb.

[Ravensouth]

Hmm well to know. I will reconnect the RX to the GND. Are not there other solutions to reduce the voltage at pin 7? Can this be due to the coil, if the pin 7 200mV a but, although I zeroed RX to 0.000V and pin 5 on the LM358 is also 0V?

[ivconic]

Hmm well to know. I will reconnect the RX to the GND. Are not there other solutions to reduce the voltage at pin 7? Can this be due to the coil, if the pin 7 200mV a but, although I zeroed RX to 0.000V and pin 5 on the LM358 is also 0V?

What LM358!?
Wire gauge you used?

[Ravensouth]

Wire Gauge = 33 AWG, 0,25mm alloyed. I'm talking about the LM358 on the circuit (IC). What makes sense now I do not know. For that I would have to look at the circuit again

[kt315]

Hmm well to know. I will reconnect the RX to the GND. Are not there other solutions to reduce the voltage at pin 7? Can this be due to the coil, if the pin 7 200mV a but, although I zeroed RX to 0.000V and pin 5 on the LM358 is also 0V?

i see you are not able understand my answers to you. read this
https://www.geotech1.com/forums/show...er-coil-inside

[Qiaozhi]

Here's Ivconics' original coil making document.

[ivconic]

Wire Gauge = 33 AWG, 0,25mm alloyed. I'm talking about the LM358 on the circuit (IC). What makes sense now I do not know. For that I would have to look at the circuit again

Don't bother with LM358 by now.
It's all about the coil.
You shall try to make another coil with closer specs.
I think you are almost there.

[kt315]

if you use a foil for shielding of coil nobody is able to help you to balance the coil.
we must see pics of your coil. not naked text from you.

[Denots]

You asked for a suggestion for an oscilloscope, I bought a hantek DSO5102P, you can get one for ?200 and it is very good, I’m still learning how to use it but for the few months I’ve owned it it’s taught me so much, you can pick up a second hand analog scope on eBay but then you won’t have as many nice features but still be able to get the job done, a digital scope will let you do a whole lot more though

[kt315]

you can buy o-scope or not buy, digital or old, - no decision if you do not inderstand what you must get.
optimal decision, THE way, for you is to buy tesoro coil on ebay "broken cable. need repair. as-is"
and close this subject. i see hundreds of threads on balancing of a coil and noone was ended with good result.
this is 'dead matter' for you. if i suggest you to begin from simplest PI detector - bara, surf - that is.

[kt315]

how REAL tesoro coil is.
you must do same way. NOT WHAT YOU TRY THERE DO.

[kt315]

.... ....