TESORO GOLDEN SABRE

[Dennis the Mennis]

Output LF353

Hi DtM -

Thanks for extra info.

W and M is a nice way to explain the detection waveform due to coil polarity. When coil is backwards, you can see why we can get a double-beep easily.

I was wondering if you have display options for displaying Multimeter type of measurements at the same time as the graph - for example, the RMS and peak voltage values?

Can you show us the outputs of your LF353 for fun?

Cheers,

-SB

Hi Simon ,

In this YouTube link : http://www.youtube.com/watch?v=TVrISTKtxAw

I've recorded some of the 'coil nulling ' : Tx vs. Rx on output of LF353 .

With this set of coils ( shielded ) I don't get any closer as 35-40 degrees ...

For the detection in All Metal Mode the shift doesn't seem to care that much...

I didn't experiment that much in Disc mode or Notch Mode because it didn't discriminate that much so I had my (wrong ? ) focus in the All Metal


best regards,

Dennis the Mennis

[habitbraker]

Hello!
I have one question regarding to operation of tgsl.
Why isnt there full voltage swing (from +8 to -5V) on the outputs of comparators(U102a/b)?
But instead of that only negative referenced to ground?
I understand that it is neeeded for n-chan jfet to work corectly(not to forward bias).
But input to comparator is +/- isnt it?

[simonbaker]

Hi Simon ,

In this YouTube link : http://www.youtube.com/watch?v=TVrISTKtxAw

I've recorded some of the 'coil nulling ' : Tx vs. Rx on output of LF353 .

With this set of coils ( shielded ) I don't get any closer as 35-40 degrees ...

For the detection in All Metal Mode the shift doesn't seem to care that much...

I didn't experiment that much in Disc mode or Notch Mode because it didn't discriminate that much so I had my (wrong ? ) focus in the All Metal


best regards,

Dennis the Mennis

Quite excellent DtM! Nice way to show your new scope.

I'm interested also in the LF353 output that drives the sync pulse, what does it look like?

I get those little spikes on the RX signal also. I suspect it is caused by the negative power rail circuitry, but not sure.

Your TX signal looks more sinusoidal than mine. Do you have the JFet in the oscillator or not?

You mentioned Notch -- did you build the full TGS circuit with the notch and battery check and everything?

I think next you should start using the discriminator mode -- that's where the fun begins!

Regards,

-SB

[simonbaker]

Hello!
I have one question regarding to operation of tgsl.
Why isnt there full voltage swing (from +8 to -5V) on the outputs of comparators(U102a/b)?
But instead of that only negative referenced to ground?
I understand that it is neeeded for n-chan jfet to work corectly(not to forward bias).
But input to comparator is +/- isnt it?

Hi habitbraker:

It seems you answered your own question well I think. Output does not go above ground so the JFets work correctly.

Maybe the answer is that the LM393 comparator requires a "pull-up" voltage for the output which is different from the supply and input voltages? So we can make the max output voltage anything we want.

The purpose is simply to make a square waves with voltage range from V- to ground from the TX sine wave input. We also put in some phase shifts with the discrimination pot and the ground balance pot before making the square waves.

Regards,

-SB

[habitbraker]

Thaks for response!
But that was my question - why output voltage of com. doesnt go above ground?

In other words - voltage on inputs of comparators is bipolar(Tx signal). Then why the output voltage is only below ground instead of -5 <--0--> +8 ??

[Gwil]

LM393 Output

Hi Habitbraker

The LM393 doesn't have the same kind of output circuit as an op amp, which can swing close to the positive and negative supply rails. Its output is the collector of an npn transistor whose emitter is connected to the negative rail - an "open collector" output. Therefore the output is either pulled down to the neg. rail or open circuit, when it is pulled up by whatever is connected to it. This feature is shown in the LM393 data sheet.

For all sorts of semiconductor data sheets, try http://www.digchip.com/

Gwil

[habitbraker]

Thanks Gwil!
This is the explanation I needed!!
Now it makes sense

[habitbraker]

Could the method described in this patent http://www.geotech1.com/pages/metdet.../US4486713.pdf be same as TGS uses?

[simonbaker]

Could the method described in this patent http://www.geotech1.com/pages/metdet.../US4486713.pdf be same as TGS uses?

It's pretty close, although the TGS does not directly compare amplitudes of the two detected channels in a single comparator like that. Rather, it uses two separate comparators, each having a reference threshold, and the two outputs are logically "AND"ed together, creating a detection logic circuit where each channel must detect the target independently for final audible detection. Also, the patent diagram has an "Absolute Value" block in each channel which I'm not sure of the function, but does not exist in the TGS.

I don't pretend to really understand the details of this patent (or others), the details are hard for me to be really clear on without exhaustive study, and patent writers always try to hedge their ideas to include myriad variations by implication.

Regards,

-SB

[dfbowers]

It's pretty close, although the TGS does not directly compare amplitudes of the two detected channels in a single comparator like that. Rather, it uses two separate comparators, each having a reference threshold, and the two outputs are logically "AND"ed together, creating a detection logic circuit where each channel must detect the target independently for final audible detection. Also, the patent diagram has an "Absolute Value" block in each channel which I'm not sure of the function, but does not exist in the TGS.

I don't pretend to really understand the details of this patent (or others), the details are hard for me to be really clear on without exhaustive study, and patent writers always try to hedge their ideas to include myriad variations by implication.

Regards,

-SB

No surprise there I guess, if there are similar. Jack Gifford's name (Tesoro company owner) is on the patent.

[simonbaker]

No surprise there I guess, if there are similar. Jack Gifford's name (Tesoro company owner) is on the patent.

Good one. I was too lazy to check. I wonder what other patents he has?

-SB

[dfbowers]

Good one. I was too lazy to check. I wonder what other patents he has?

-SB

Well, I made some assumptions when I said that Jack was the owner, but Tesoro is owned by the Gifford family.

Here is the history of the company:
http://www.tesoro.com/info/about/

[simonbaker]

Well, I made some assumptions when I said that Jack was the owner, but Tesoro is owned by the Gifford family.

Here is the history of the company:
http://www.tesoro.com/info/about/

I like their philosophy of no frills detectors. I think they accomplished that very well.

Cheers!

-SB

[Dennis the Mennis]

Quite excellent DtM! Nice way to show your new scope.

I'm interested also in the LF353 output that drives the sync pulse, what does it look like?

I get those little spikes on the RX signal also. I suspect it is caused by the negative power rail circuitry, but not sure.

Your TX signal looks more sinusoidal than mine. Do you have the JFet in the oscillator or not?

You mentioned Notch -- did you build the full TGS circuit with the notch and battery check and everything?

I think next you should start using the discriminator mode -- that's where the fun begins!

Regards,

-SB

Hi Simon ,

This the output of the LF353 pin 1 that drives the sync pulse .
Although there is some distortion it seems to dissapear in the next stage.



The next 2 images are the outputs of the LM393 ...









And yes , I did build the complete TGS with notch and batterycheck : When I was reading all the posts at that moment the TGS had proven itself ... I thought .

I saw the TGSL pcb's offered by Silverdog , maybe my next project.

Whenever you need some more images for comparison let me know.

kind regards ,

Dennis the Mennis

[ApBerg]

Hallo Danny,

Think you have not a good receive signal, tray to adjust it with the 'receive cap' .

Make a 'Receive Cap' test circuit and see how the receive signal changes...