Balanced VLF Tx

[WM6]

If someone wish to try Davor's Clapp-Version of his VLF TX Balanced Oscillator, this DipTrace design may help:

[WM6]

Some power switching scope sim. on Clapp Balanced VLF TX:

[Aziz]

You Beauty Balanced Sine-Wave!

Hi all,

has anyone tried the super-duper oscillator "invention" yet?
Me saying: Wow! Wow!

It makes sense to make the regulation control loop to adapt it into existing VLF projects. But I personally don't need the regulation in DSP software.

BTW, the oscillator works very fine and I couldn't find critical issues. The spice sims are working correct and giving comparable results to the real world. Oh yes!, a perfect sine wave too.


Cheers,
Aziz

[WM6]

It makes sense to make the regulation control loop to adapt it into existing VLF projects.

Can you suggest / draw such control loop in here present TX oscillator?

But I personally don't need the regulation in DSP software.

Hi Aziz, do you intend to write DSP software for your PC Sound Card project?

Without your real contribution in writing software support "PC Sound Card MD" will become dead project.

I cannot see anyone here except you capable to write software part of solution.

Ideal solution: using PC tablet and software written under android OS.

[Davor]

BTW, the oscillator works very fine and I couldn't find critical issues. The spice sims are working correct and giving comparable results to the real world. Oh yes!, a perfect sine wave too.

Which one did you build?

[lonelyWOLF]

Aziz-Davor s (magic emiter inductors) tx
scope knops at 5v DC time .2us

[Aziz]

Which one did you build?

Post #159:
http://www.geotech1.com/forums/showt...089#post160089

The one I'm following with my laptop/netbook/tablet PC VLF project.
Even it hasn't an RX amplifier (and hence is a passive version), the sensitivity is remarkable. And I haven't used a tuned RX coil yet (no capacitor connected and tuned yet) .
The lock-on onto the TX reference is working fine. I just have to compensate the effects of TX coil voltage variation (some kind of digital regulation loop). It will also compensate the voltage drift (battery voltage diminishing), ground effects, losses, etc.. .

Aziz

[Aziz]

Aziz-Davor s (magic emiter inductors) tx
scope knops at 5v DC time .2us

Brilliant half sine waves! That's the real magic there.
And very nice sine waves.
Well done!
Aziz

[Aziz]

Can you suggest / draw such control loop in here present TX oscillator?

Hi Aziz, do you intend to write DSP software for your PC Sound Card project?

Without your real contribution in writing software support "PC Sound Card MD" will become dead project.

I cannot see anyone here except you capable to write software part of solution.

Ideal solution: using PC tablet and software written under android OS.

Hi,

the control loop hardware part is trivial. It should just keep the TX coil voltage constant. Best implemented in the emitter section of the oscillator.

I wouldn't do the DSP software in Android platforms (no money, no fun and I'm totally poor and bankrupt).
The DSP software is trivial too. You need FFT, lock-in amp and some DSP implementation.

When I do it and give it for free, all the big players would hate & kill me.
*LOL*
Aziz

[Davor]

Now this is actually a bad idea: balancing the existing single ended Tx. There are several good reasons why this is a bad idea, and most important is that it requires a floating Tx coil. Any configuration with grounded Tx coil is not going to work well. It also can't cancel 2nd harmonic, and the only advantage could be for supplying a DD coil with semi-balanced Tx signal. It would reduce Tx/Rx capacitive coupling, but otherwise it ... is not a good idea.

Maybe someone will find some use for it.

The right side is the existing circuitry, and the left side is a single ended coil replacement circuitry. Please observe the 2nd harmonic (it is optimised!) which is certainly not cancelled.

[Davor]

A small addition, I played with my old friend 4049 and it seem that it will be a perfect platform for an off resonance oscillator based on a cross-quad configuration. Total current is about 8mA and maximum load of any gate is less than 4mA at any moment.

Pure Zen.

[WM6]

A small addition, I played with my old friend 4049 and it seem that it will be a perfect platform for an off resonance oscillator based on a cross-quad configuration. Total current is about 8mA and maximum load of any gate is less than 4mA at any moment.

Pure Zen.

Thank you Davor, very much. I am very interesting in this design and plan to play with it.
At which point of 4094 off-res-oscillator can be best to take signal (to connect) for the following stages like buffer amplifier?

[Davor]

At Vss
It is already demodulated there, and there is no trace of a fundamental frequency. The major problem is pushing such oscillator into a regime that is just below saturation. It can be done quite simply by tuning the R14.

[Davor]

Here is my sim of the off-resonance oscillator solution with 4049. It is most sensitive to targets ~30us tau, so I guess it qualifies. A pair of 22pF capacitors set it off. I designed it as suggested in a Carl's and George's book - with a choke. Now, it is a bit tricky, because in off-resonance you are using a coil at a frequency where the Q is greatly diminished and it influences the amplitude of oscillation. Chokes are not famous for their high Q so oscillation level MUST be tuned. You tune it by R4.

Feel free to play with this model. Most probably you'll come up to something more interesting than I have. It is supplied with a switched target with 20us tau, and you can change it directly by setting the inductance of the coil. If you need 40us, just put 40uH for a coil. If you need copper, just put 150uH. You can also play with coupling.

[Aziz]

A small addition, I played with my old friend 4049 and it seem that it will be a perfect platform for an off resonance oscillator based on a cross-quad configuration. Total current is about 8mA and maximum load of any gate is less than 4mA at any moment.

Pure Zen.

Beautiful. I like it.
Aziz