Aquasound

[pustareka]

execuse me jump in aqua topic. heatkit very good ingeneering. relaxation oscillator and precise nullig coils. worth study and replication. as had been told by ancients: what is difficult - it is false. this project is simple and genous very great for selfmade teach.

[dbanner]

You may also try a RX coil without CT, optional arrangement from the patent.
See if you still have the distortion.

[Altair]

If I eliminate the bucking coils and try to balance RX and TX like a normal OO, everithings goes well; no distortion at all.

[dbanner]

Soon I hope to return to this project, in a few days time I will begin testing a new coil.

[dbanner]

A distortion of the RX signal might be caused by an imbalance of the two buck coils.
That is probably why the patent specifically staes to balance the RX for zero phase shift, the feedback pots will fine balance the voltage null.
I am only guessing what could be the problem.

Just wind the buck coils to be identical, so they impart equal effect on the rx. Use sufficient number of turns to bring the rx in the ballpark of null, but with zero phase. Let the feedback pot do the rest.

[Altair]

Concentric coplanar coil balancing seem to be not an easy task. The two bucking coils setting left me an high residual voltage (about 88 mV). Oscilloscope show me a distortion of RX signal that is not present without bucking coils and this is the cause of residual high voltage.

[dbanner]

DB, i had told how to get deep null and how whites gets deep null. 0.00uV. you have to read again a thread.
https://www.geotech1.com/forums/show...er-coil-inside

Ah yes, I remember now, a closed loop. Thanks for that kt.

[kt315]

DB, i had told how to get deep null and how whites gets deep null. 0.00uV. you have to read again a thread.

https://www.geotech1.com/forums/showthread.php?24481-whites-treasuremaster-coil-inside

[dbanner]

Tomorrow I begin making the PCB. So we can make this project together and compare results. Will be good experience.
I will put pics of my finished PCB tommorow.

[Altair]

Also, 6mv peak to peak was achieved in White's concentric coplanar type coil. In the patent for that coil is use of electrostatic shield ( a layer of foil) between the RX coil and the feedback coils to prevent capacitative coupling between Rx and feedback. This electrostatic shield is connected to the D.C ground.

Maybe this is required to be able to achieve a deep null.

Thank you dbanner!

You focused me on an important detail I was missing!

[dbanner]

Also, 6mv peak to peak was achieved in White's concentric coplanar type coil. In the patent for that coil is use of electrostatic shield ( a layer of foil) between the RX coil and the feedback coils to prevent capacitative coupling between Rx and feedback. This electrostatic shield is connected to the D.C ground.

Maybe this is required to be able to achieve a deep null.

[Altair]

Connect the feedback pots and adjust. You should be able to transition through either side of 0 volts on the RX V(out). Perfect null is impossible by mechanical geometry unless you put small tuning inductor in series. Only possible by electrical means.

Or you may wish to play around with small loops of wire for entire day. Remember there are two feedback windings, hence two fine tuning loops.

Yes, I will see with pots if low nulling is really needed.

[dbanner]

Another idea would be to balance each half separately and then connect together, although I never tried it.

[dbanner]

Connect the feedback pots and adjust. You should be able to transition through either side of 0 volts on the RX V(out). Perfect null is impossible by mechanical geometry unless you put small tuning inductor in series. Only possible by electrical means.

Or you may wish to play around with small loops of wire for entire day. Remember there are two feedback windings, hence two fine tuning loops.

[Altair]

I am trying to balance my center tapped concentric coplanar coil, it's not an easy task! playing a bit I get a minimum of about 88mV that is not ideal indeed. the difficult is also to mantain the same inductance of the two semi-coils due to different path of wires that occour during winding.
Any tips are welcome.