DOD coil for TDI

[WM6]

From the other side, why the Tx signal to decrease the Rx signal????? Here i use seperate coils for Tx and Rx.

Probably cos TX oscillations induce direct parasitic signal to RX coil that can suppress, change or even negate targets signals.

[Geo]

I connected a 1k resistor parallel to damping resistor and now the Tx waveform is "perfect".
Depth remains low .

[Geo]

There is a crack at RX signal and i can't fix it.
Why????

[Tinkerer]

There is a crack at RX signal and i can't fix it.
Why????

[ATTACH]34295[/ATTACH]

Do you have damping resistors on the RX coils?

[Geo]

Yes, one 680R at Rx input. Now i will try one resistor for every D winding and will try for a better null.
Problem is that i"ll have free time after one week (maybe).
When i destroy the null of one D (not everyone D) then i have big signal without this "crack". Maybe bad balance between two D and O coil.

New coil... new problems!!!. As we say here at Greece ""new donkey new walked""

[Tinkerer]

Yes, one 680R at Rx input. Now i will try one resistor for every D winding and will try for a better null.
Problem is that i"ll have free time after one week (maybe).
When i destroy the null of one D (not everyone D) then i have big signal without this "crack". Maybe bad balance between two D and O coil.

New coil... new problems!!!. As we say here at Greece ""new donkey new walked""

You need to put a damping resistor on the TX coil and on each RX coil.
Then you can try to null the 2 RX coils.
For a perfect null you need to adjust the phases of the two RX coils, shifting the phase of one coil, the match the other coil.

[Geo]

DOD coil did not work for me . Near to null position the signal is very deformed, maybe because D and O coils are not symetrical.
Now i try a OOO coil and it seems to be better but i have not finish it yet.

[Geo]

Finally i finished the OOO coil and tried it at field. Tx coil has 30cm diameter and Rx coils have 24cm diameter.
Results are good, so i have about 10% more depth than the 12" original coil.
Also i have the same depth with GB=on or GB=off. This is because the coil is very quite and i can work with GB=on and potentiometer at "11". Ground at field is so mineralised that with 12" coil and Gb=on i have gound balance at position "6". The only basic problem is the big dimentions. Maybe i must give another try at DOD coil. Also i must give more gain at TDI because is so quite.

[WM6]

Maybe i must give another try at DOD coil.

Thanks for report Geo. It is worth to give OOO a second try.

Balancing principle are the same with OOO, but somewhat more delicate, cause of shape.

Dimensions of OOO shape outcome problematic in practical hunting.

[Geo]

Hi wm6.
I will try the DOD again on new year.
With DOD we have smaller dimentions so if it works ok then i want to construct a 50... 60 cm diameter coil.
But it need more experiments...

Regards

[nickel_n]

Hi Geo
What are the specs of your OOO coil? Tx, Rx inductance? damping R ?and wire gauge?

[Geo]

Tx coil is 330uH, 30cm diameter with wire 0.6mm.
Rx coils are 24cm diameter with wire 0.3mm, near to 400uh and everyone has a 470 Ohm damping resistance.