Balanced VLF Tx

[Aziz]

Pretty nice... for comics industry, how about real life?
Does anybody of you ever tried to materialize those comics?
Pals you are talking too much and now is time to transfer all those in material world.
Make something from all of that!
How about one simple metal detector project... for a start?
Cheers!

Hi Ivconic,

ok, I have provided the hardware part for the nice toy.
Who is going to make the DSP software part now?

This "comic" is a brilliant simple and powerful detector platform to implement the whole VLF detector technology in software. It looks really very simple ... (but can knock out a lot of VLF detectors *LOL*).

Cheers,
Aziz

[WM6]

At least i did draw pcb...

Nice work ivconic. You use Davor's solution.

Can you post black-white slide too? And schematic (if) you draw. Seems R2 is missing in your PCB?

[Davor]

Of course
One must adopt marketing ways of expressing ideas in nowadays economy. The funniest part - I'm not selling anything!

[Sergey_P]

and as a bonus gets 60% more coil current for free

I=U/(wL)

[ivconic]

At least i did draw pcb...

[ivconic]

Pretty nice... for comics industry, how about real life?
Does anybody of you ever tried to materialize those comics?
Pals you are talking too much and now is time to transfer all those in material world.
Make something from all of that!
How about one simple metal detector project... for a start?
Cheers!

[Aziz]

Must see my new VLF oscillator detector controller.
BTW, you can play with the spice file if you like.

SingleFrequencyOsc-VLF-passive-pnp-03.zip



Cheers,
Aziz

[Carl-NC]

Good morning again guys,

(was very late last night *LOL*)

I want to mention, that the crucial point and all of the merit of the whole circuit is in the magic emitter inductor(s). And I haven't seen any LC oscillator having an feedback like the emitter inductor. The transistors base current is a half sine current (owed to the fact of emitter inductor PS: ... oops, b.s. detected! no, the cross-coupled voltage is a half sine anyway but the supply voltage over the oscillator is a half sine, which is owed to the fact of using emitter inductor) and the whole current injection into the resonant LC circuit is some kind of frequency locked current injection.

Are emitter inductors a "don't do"-rule in electronics? If yes, oooops sorry!
*LOL*

Cheers,
Aziz

PS: added, b.s. killed

Emitter inductors are common with on-chip VCO's. My 2.4GHz VCO had one, and I copied what everyone else was doing.

[Davor]

This is a slam dunk

I played just a little bit with now famous cross-quad oscillator and came up to something beautiful. I combined my initial design with Aziz' and mixed in some Clapp-style tricks, and voilà - a booster cross-quad configuration. I also dropped the emitter resistors for simplicity that resulted in somewhat higher 3rd harmonic, but let it be ... for now.
So what you see is an oscillator that will use my existing beloved FKK coil with Musketeer specs for IGSL, working at precisely where it is supposed to oscillate, at 60% more voltage and current than it is supposed to provide, without Aziz' chokes. Vcc bound of course.
There is a caveat though. The oscillator won't start if the series capacitors are not at least 4 times larger than the lateral ones, and I guess it is highly advisable to use foil capacitors as series ones, which may turn a bit spacious.

Whoever cares to do so may rejuvenate the existing rig using the existing coil (provided it is not nailed on one side to the ground ) with the balanced oscillator, and as a bonus gets 60% more coil current for free

Enjoy, a Cross-Quad Clapp-style booster oscillator:

[Aziz]

Good morning again guys,

(was very late last night *LOL*)

I want to mention, that the crucial point and all of the merit of the whole circuit is in the magic emitter inductor(s). And I haven't seen any LC oscillator having an feedback like the emitter inductor. The transistors base current is a half sine current (owed to the fact of emitter inductor PS: ... oops, b.s. detected! no, the cross-coupled voltage is a half sine anyway but the supply voltage over the oscillator is a half sine, which is owed to the fact of using emitter inductor) and the whole current injection into the resonant LC circuit is some kind of frequency locked current injection.

Are emitter inductors a "don't do"-rule in electronics? If yes, oooops sorry!
*LOL*

Cheers,
Aziz

PS: added, b.s. killed

[Dave J.]

And having fun doing it!

[Davor]

So in fact we are re-stirring the stale waters

[Dave J.]

See my post in the 4-quadrant thread.

The Teknetics T2 (Hartley topology, top half of a full bridge) uses an emitter inductor, but my more recent designs are not Hartley topology and don't use an emitter inductor. Chinese counterfeiters already know all this, no harm in telling y'all.

In general I favor transmitters that are Vcc-bound. However I've done it the other way successfully using active transmitter regulation via a feedback loop. Perhaps Carl has thrown a 'scope probe loop over the top of an MXT searchcoil while lowering it to a tub of magnetite sand, and will be tempted to comment on what he saw...............................

Active transmitter regulation isn't even new, Jack Gifford was doing it in the 1970's. Funny as it seems now, the transmitter is what was regulated via a feedback loop and the rest of the system wasn't regulated. The 1975-85 era was a revolutionary era for metal detectors, lots of new stuff being tried by several very good engineers and a lot of what's on the market today is based on what emerged from that era.

--Dave J.

[Davor]

True, but the emitter inductor is a novel twist to it. This approach may liven some existing rigs with the existing coils as it gives more bang per supply voltage.
I'm still inclined towards an initial solution that is Vcc bound because it is considerably less noisy.

So cross-coupled H-bridge is christened cross-quad? Nice and catchy.

[Carl-NC]

[ATTACH]21782[/ATTACH]

This is essentially identical to a 2.4GHz VCO I did for a GSM chip many yrs ago. It used an on-chip center-tapped spiral inductor, only 3 turns total.

Still, the cross-quad is better for MDs, IMO.