TESORO GOLDEN SABRE

[Max]

Hi Max

Air test : The coin with 25mm diameter from 30cm of coil .it isn’t very
Good result when compare with your built and ivconic
Also the test area contains heavy electrical interference and noises.
Because My office placed in power cable factory



I using shielded wire with 2mm dia .



The chair, check it, contain very small staples. Not under coil, far it
Thanks for your guide .
Best regards.

Hi,
ok, but 2.5cm coin at 30cm is not that bad too. It's a good result for an homemade VLF, considering also the TGS/TGSL has not a very powerful transmitter stage, but weak.

The wires are ok, and chair also.

I think then that maybe you need more careful tuning at coil, and find a place with less noise to explore all sensitivity of device.

If too noise around you'll not spot the real maximum sens of device cause noise will prevent you running it (stable) at maximum sens.

Kind regards,
Max

[Max]

Another point: minimum sensitivity threshold is about 3.3 mV -- so theoretically we can't detect anything that is less than that at output of LM308. If people say detector is quiet, then what good is making circuit noise lower, because it is already below sensitivity threshold? If you currently use sensitivity at maximum sens, then making noise lower is only useful if you can then increase gain too.

So, if we have zero circuit noise, and no RF, etc., then existing design of sensitivity control limits depth of target. A little noise actually helps because it adds to target signal and lifts above sensitivity threshold so you hear it. But noise will make crappy audio because choppy when just at sensitivity threshold.

So if we make very low noise circuit, maybe need to make sensitivity threshold lower and increase gain.

However, if make sensitivity threshold lower, we have to watch out for complete recovery -- even tiny amount of residue can interfere with threshold if low enough. I notice this with LTSpice when trying slower response filters - recovery residue is problem for sensitivity threshold.

Just trying to learn all these factors, better know how to build good TGSL.

Cheers,

-SB

Hi,
yes you're right. If the device can run absoutely quiet there's no reason to limit the gain too much, so the sensitivity.

Of course, that's depends not only on design but on e.g. S/N due to construction (board, wires, components, soldering, ground plane if any, cleaning process, kind of box employed, wiring to coil etc etc)

In good construction practice, with very hi S/N I think is good push lower that threshold, gaining about detection.

I will try it soon.

Kind regards,
Max

[Alexismex]

Thank you very much Max for your good explanation on dual amp, many times i think about that without response , now thank to you it is clear in my mind why it is better to design with dual amp,you win a 10 and a good beer , thank again,
saludos from Mexico
Alexis

[ivconic]

Hi,

a portable oscope will do that. I can't test for that but will be really interesting.

The big part of noise to consider is about 3 factors:
- electrical noise
- rf noise
- internal noise

For electrical noise (that always produce low frequency radiated EM noise too) I mean very low frequency kind of noise... like from e.g. a fluorescent lamp near... an electric motor running... oscillations produced in the bounce of a switch inside home... and similar stuff.

For RF noise I mean expecially radio noise from VLF/LW range to some MHz (short waves) + some very near transmitter running also in VHF/Frequency modulation too.

Which problems ?

Electrical noise is easy to see at home... any time someone will switch a lamp on I get sound in my TGS/TGSL from meters away... also from 15meters away! That's cause all the house is full of copper wires around... and any fluctuation will be a near fluctuation too... that propagates by wires and on other e.g. equipment like power supply, scope etc

At the end... if using battery, the stuff is about the same... I get sound from electrical noise at distance.

The RF noise is more subtle: you can't see it unless you know there is or you're looking for it.

When you're near a powerful transmitter , for example, you get all that noise for free!

That's disappointing sometimes. In a city/town you'll always get some amount of RF noise... and also e.g. mobile phones transmitters will give you troubles.

The advantage is that a thin shield will block most of RF noise!

But then electrical noise you'll not solve even with shield.

Internal noise depends of components: use less noise rated and will get real advantages. E.g. avoid old TL062...and use TL072/TL082 and also LM358 if you can (use e.g. TLC2262 there or other), you'll notice the difference.

Kind regards,
Max

Thanks Max,
you put some light on my doubts. I wasnt sure but had some simillar doubts. Now is more clear to me and makes more sence.
Regards!

[simonbaker]

Hi,
a portable oscope will do that. I can't test for that but will be really interesting.

The big part of noise to consider is about 3 factors:
- electrical noise
- rf noise
- internal noise

For electrical noise (that always produce low frequency radiated EM noise too) I mean very low frequency kind of noise... like from e.g. a fluorescent lamp near... an electric motor running... oscillations produced in the bounce of a switch inside home... and similar stuff.

For RF noise I mean expecially radio noise from VLF/LW range to some MHz (short waves) + some very near transmitter running also in VHF/Frequency modulation too.

Which problems ?

Electrical noise is easy to see at home... any time someone will switch a lamp on I get sound in my TGS/TGSL from meters away... also from 15meters away! That's cause all the house is full of copper wires around... and any fluctuation will be a near fluctuation too... that propagates by wires and on other e.g. equipment like power supply, scope etc

At the end... if using battery, the stuff is about the same... I get sound from electrical noise at distance.

The RF noise is more subtle: you can't see it unless you know there is or you're looking for it.

When you're near a powerful transmitter , for example, you get all that noise for free!

That's disappointing sometimes. In a city/town you'll always get some amount of RF noise... and also e.g. mobile phones transmitters will give you troubles.

The advantage is that a thin shield will block most of RF noise!

But then electrical noise you'll not solve even with shield.

Internal noise depends of components: use less noise rated and will get real advantages. E.g. avoid old TL062...and use TL072/TL082 and also LM358 if you can (use e.g. TLC2262 there or other), you'll notice the difference.

Kind regards,
Max

Another point: minimum sensitivity threshold is about 3.3 mV -- so theoretically we can't detect anything that is less than that at output of LM308. If people say detector is quiet, then what good is making circuit noise lower, because it is already below sensitivity threshold? If you currently use sensitivity at maximum sens, then making noise lower is only useful if you can then increase gain too.

So, if we have zero circuit noise, and no RF, etc., then existing design of sensitivity control limits depth of target. A little noise actually helps because it adds to target signal and lifts above sensitivity threshold so you hear it. But noise will make crappy audio because choppy when just at sensitivity threshold.

So if we make very low noise circuit, maybe need to make sensitivity threshold lower and increase gain.

However, if make sensitivity threshold lower, we have to watch out for complete recovery -- even tiny amount of residue can interfere with threshold if low enough. I notice this with LTSpice when trying slower response filters - recovery residue is problem for sensitivity threshold.

Just trying to learn all these factors, better know how to build good TGSL.

Cheers,

-SB

[aft_72005]

Hi Max

Air test : The coin with 25mm diameter from 30cm of coil .it isn’t very
Good result when compare with your built and ivconic
Also the test area contains heavy electrical interference and noises.
Because My office placed in power cable factory

why don't you try something shielded cable instead ?

I using shielded wire with 2mm dia .

Also, the CHAIR ! Are you sure the chair has no metal inside like iron rivets or nails ?

The chair, check it, contain very small staples. Not under coil, far it
Thanks for your guide .
Best regards.

[Max]

I am interested in noise people talk about, where it is from.

In my laboratory (spare bedroom, no workbench), with my ridiculous unshielded coil and breadboard circuit, the coil creates the major part of noise. Not unexpected, it is a huge antenna for any kind of emf.

If I disconnect coil from circuit, noise drops down factor of ten (but still a lot).

So only way to observe typical working noise must be outside I assume. (But then scope not available. Maybe can run it from car battery.)

I am interested if anyone can do this: get outside with a scope and detector. Measure noise (I guess at output of LM308 ) with coil connected, then disconnected. Then measure noise shorting inputs to op amps one at a time up the chain, how does the noise change? What is the critical source of noise?

You would guess that LF353 pre-amp and LM358 front stage would be where noise is critical. Why is LM358 not an ultra low-noise component, like a biFet op amp?

Another source of noise would be subtle jitter in the JFet gate driver circuits. Very difficult to see because such big strong signal. But if LM393 triggers at slightly different points, it shifts driver square wave a little, causes "phase noise" so to speak. A little noise in the TX oscillator can change the zero crossings of the the LM393 that makes the gate driver signal, making "phase noise". But you hope that the same noise goes into the coil and back out the RX signal and gets balanced out. Who knows.

The wires from the descrim switch of course can pick up noise, but is after the LMM393, hopefully swamped and no effect. But that noise can maybe feed through the JFet gate to the JFet Source and get into the LM358 input.

So main experiments are:

1- noise with coil.
2 - noise with coil disconnected.
3 - noise with front LM358 input grounded before the 100K resistor.
4 - noise with front LM358 input grounded directly.

-SB

Hi,
a portable oscope will do that. I can't test for that but will be really interesting.

The big part of noise to consider is about 3 factors:
- electrical noise
- rf noise
- internal noise

For electrical noise (that always produce low frequency radiated EM noise too) I mean very low frequency kind of noise... like from e.g. a fluorescent lamp near... an electric motor running... oscillations produced in the bounce of a switch inside home... and similar stuff.

For RF noise I mean expecially radio noise from VLF/LW range to some MHz (short waves) + some very near transmitter running also in VHF/Frequency modulation too.

Which problems ?

Electrical noise is easy to see at home... any time someone will switch a lamp on I get sound in my TGS/TGSL from meters away... also from 15meters away! That's cause all the house is full of copper wires around... and any fluctuation will be a near fluctuation too... that propagates by wires and on other e.g. equipment like power supply, scope etc

At the end... if using battery, the stuff is about the same... I get sound from electrical noise at distance.

The RF noise is more subtle: you can't see it unless you know there is or you're looking for it.

When you're near a powerful transmitter , for example, you get all that noise for free!

That's disappointing sometimes. In a city/town you'll always get some amount of RF noise... and also e.g. mobile phones transmitters will give you troubles.

The advantage is that a thin shield will block most of RF noise!

But then electrical noise you'll not solve even with shield.

Internal noise depends of components: use less noise rated and will get real advantages. E.g. avoid old TL062...and use TL072/TL082 and also LM358 if you can (use e.g. TLC2262 there or other), you'll notice the difference.

Kind regards,
Max

[Max]

Yes i have almost the same experiences.
Usually i put TL082 when not having LF353, works just fine there. NE5532 is just not working at present setup. I think it will work just fine too, if we readjust components arround it. TL072 is actually TL082 so..same story - it can be used there pretty successfully.
Recently i got LS204 in metalic case. Not tested yet, but i will test those for sure.
It is not a big deal to replace and readjust front end at TGSL.
What bugs me more are LM308 and LM393. OK..TL081 also tested instead LM308 and to tell you the truth; those really do the job with less noise.
But LM393 is a real pain in the .......coil!!!
I am sure that TLC2262 can replace those, even work better, but i simply cant find those in local shops!
Or even better TLV2262.

Another thing...LM358 could be replaced with something better, but which one? I was thinking to put there 4 x opamp instead 2x LM358.
Is it good idea?
I am planing to redraw pcb for that matters soon.
What should i consider to put there? TL074,TL084? LM324? LF444?
So far i used mainly LM324 in many circuits and those suits all the demands.

I am quite unexperienced refering some specific questions, so i will freely ask here, please dont laugh;
are there any changes (benefits,drawbacks) if two double op-amps are replaced with one 4xop-amp? Refering hums,power drains, signal paths etc.etc...?
Reasons why am i asking this funny question is more than naive..but hey, i want to learn and be sure.
Theoretically it should be the same thing; 2x double or 1xquadro...same thing.
But in practice i noticed some thing; usually those cheap chinesse detectors DO have quadros more than singles? Why? Production costs?
Other hand, branded machines usually do have plenty of "doubles" and rarelly some "quadro"....
Ok...many branded's do have TL074, 27m9, LF444 and similars... and also more "doubles" but my (weird) statistics is pushing me to start thinking on this as some special reason.
I havent seen any 27mxx or LF... on chinesse toys, but mostly LM324's and TL064's. Again, on branded machines usually are mentioned and very rare "quadros" like TL064 and LM324..?
Is this only my imagination or there is something else there?

Hi,
the LS204 is good there, tested too... (just forgot about before you wrote in your post...) so can use there.

The 5532 is a transistor input amplifier... and probably the reason why it's not so smart there is related to that. Fet amplifiers are fairly better at TGS preamp.

You're right about the chinese Mds don't use the good components... reasons are related to costs... cause also they need to product hundred thousands of that machines... and they must cost really few , so single piece cost is a big issue in that scale of production.

They also use quads more for similar reasons... the quads have often costs similar to a dual ! So if use e.g. TL064 the cost (on hi-volume) is really near a TL062 and not 2xTL062 as one could expect: that's related to manifacturing of device... making a quad is not more expensive than making a dual in the silicon technology... and having one enclosure/package instead of 2 make , really, a cost difference instead. A machine for packaging will need double the time to make 2 epoxy enclosures instead of one, larger.

The difference... there IS. It's mostly related to noise propagation: even in quality parts, with extremely good channel separation, you'll get troubles from very near tracks of signal path! In cheap op amps the channel separation is rarely an issue... it's average and LM324 is an example of that.

We must think our MDs like hi-fi audio devices: most audio designers very often use dual op amps instead of quads just for the reasons of above.

Then there's also the supply rejection issue...to consider. A quad (not always) usually do not offer enough supply rejection compared to a dual design.

Are details... but important either when making audio hi-fi designs or good MDs, that's why big players like the dual op amps and usually avoid the quads.

An example: in Vladimir's TGSL design you use the TL082 instead of 2xLm308, right ? How do you feel about ?

I made the board, works good, but noticed that there are problems with the TL instead of 2xLM308... and problems are not related much to the quality of op amp (TL082 is better about noise respect to LM308 ) but to the too near signal tracks there: it's a layout problem!

So, the details are important when try to put to the extreme a good design.

We sacrifice space and components for the best results.

Kind regards,
Max

[simonbaker]

coil noise

I am interested in noise people talk about, where it is from.

In my laboratory (spare bedroom, no workbench), with my ridiculous unshielded coil and breadboard circuit, the coil creates the major part of noise. Not unexpected, it is a huge antenna for any kind of emf.

If I disconnect coil from circuit, noise drops down factor of ten (but still a lot).

So only way to observe typical working noise must be outside I assume. (But then scope not available. Maybe can run it from car battery.)

I am interested if anyone can do this: get outside with a scope and detector. Measure noise (I guess at output of LM308 ) with coil connected, then disconnected. Then measure noise shorting inputs to op amps one at a time up the chain, how does the noise change? What is the critical source of noise?

You would guess that LF353 pre-amp and LM358 front stage would be where noise is critical. Why is LM358 not an ultra low-noise component, like a biFet op amp?

Another source of noise would be subtle jitter in the JFet gate driver circuits. Very difficult to see because such big strong signal. But if LM393 triggers at slightly different points, it shifts driver square wave a little, causes "phase noise" so to speak. A little noise in the TX oscillator can change the zero crossings of the the LM393 that makes the gate driver signal, making "phase noise". But you hope that the same noise goes into the coil and back out the RX signal and gets balanced out. Who knows.

The wires from the descrim switch of course can pick up noise, but is after the LMM393, hopefully swamped and no effect. But that noise can maybe feed through the JFet gate to the JFet Source and get into the LM358 input.

So main experiments are:

1- noise with coil.
2 - noise with coil disconnected.
3 - noise with front LM358 input grounded before the 100K resistor.
4 - noise with front LM358 input grounded directly.

-SB

[ivconic]

Hi,
today I tryed again and again to spot the difference between LF353 (used in original design) and TL072...

I made that a number of times so didn't expect anything new... this post just to signal what I think of both.

So far I tested also TL082, TL062, TLC2262, MC33178 and NE5532A at that place.

Start with others... OK TL082 is same of TL072 so read ahead for details. TL062 is not good there, too noise. TLC2262 and MC33178 work somehow... but not that good there.

The NE5532, just forget about, doesn't work any good.

TL072 is good at preamp: I use always during testing and it's good always, same for TL082, are stable, not much noise... and good performance.

So what's the difference between 072 and old LF353 ???

It's more sens with LF353, not much, but more.

Say that can add up to 10% more performances than on TL072, so if e.g. you have 1eur at 30cm with TL072 expect also 33cm with the LF353.

The price is more chatters, sometimes you trigger detection and the LF353 generate more "oscillations" in the output sound that last for a while... on TL072 you'll not see that, if everything right.

That's it.

I'd like to know of other comparision too... with other low noise stuff.

Kind regards,
Max

Yes i have almost the same experiences.
Usually i put TL082 when not having LF353, works just fine there. NE5532 is just not working at present setup. I think it will work just fine too, if we readjust components arround it. TL072 is actually TL082 so..same story - it can be used there pretty successfully.
Recently i got LS204 in metalic case. Not tested yet, but i will test those for sure.
It is not a big deal to replace and readjust front end at TGSL.
What bugs me more are LM308 and LM393. OK..TL081 also tested instead LM308 and to tell you the truth; those really do the job with less noise.
But LM393 is a real pain in the .......coil!!!
I am sure that TLC2262 can replace those, even work better, but i simply cant find those in local shops!
Or even better TLV2262.

Another thing...LM358 could be replaced with something better, but which one? I was thinking to put there 4 x opamp instead 2x LM358.
Is it good idea?
I am planing to redraw pcb for that matters soon.
What should i consider to put there? TL074,TL084? LM324? LF444?
So far i used mainly LM324 in many circuits and those suits all the demands.

I am quite unexperienced refering some specific questions, so i will freely ask here, please dont laugh;
are there any changes (benefits,drawbacks) if two double op-amps are replaced with one 4xop-amp? Refering hums,power drains, signal paths etc.etc...?
Reasons why am i asking this funny question is more than naive..but hey, i want to learn and be sure.
Theoretically it should be the same thing; 2x double or 1xquadro...same thing.
But in practice i noticed some thing; usually those cheap chinesse detectors DO have quadros more than singles? Why? Production costs?
Other hand, branded machines usually do have plenty of "doubles" and rarelly some "quadro"....
Ok...many branded's do have TL074, 27m9, LF444 and similars... and also more "doubles" but my (weird) statistics is pushing me to start thinking on this as some special reason.
I havent seen any 27mxx or LF... on chinesse toys, but mostly LM324's and TL064's. Again, on branded machines usually are mentioned and very rare "quadros" like TL064 and LM324..?
Is this only my imagination or there is something else there?

[eclipse]

Hi,
yes... it's old... it's a Thomson-CSF's metallic LF353... very old!

http://en.wikipedia.org/wiki/Thomson-CSF

Kind regards,
Max

More than 10 years old... few years before I first heard what's a transistor
no wonder I haven't seen this logo before.
I like the weapon avatar mania, Ill stick with the clever cavemen for now

[Max]

Speaking of Thom(p)son...

Max...here is better avatar for you !!!

Uhm... I like the AK too much...

[ivconic]

Speaking of Thom(p)son...

Max...here is better avatar for you !!!

[Max]

LF353 vs TL072 etc

Hi,
today I tryed again and again to spot the difference between LF353 (used in original design) and TL072...

I made that a number of times so didn't expect anything new... this post just to signal what I think of both.

So far I tested also TL082, TL062, TLC2262, MC33178 and NE5532A at that place.

Start with others... OK TL082 is same of TL072 so read ahead for details. TL062 is not good there, too noise. TLC2262 and MC33178 work somehow... but not that good there.

The NE5532, just forget about, doesn't work any good.

TL072 is good at preamp: I use always during testing and it's good always, same for TL082, are stable, not much noise... and good performance.

So what's the difference between 072 and old LF353 ???

It's more sens with LF353, not much, but more.

Say that can add up to 10% more performances than on TL072, so if e.g. you have 1eur at 30cm with TL072 expect also 33cm with the LF353.

The price is more chatters, sometimes you trigger detection and the LF353 generate more "oscillations" in the output sound that last for a while... on TL072 you'll not see that, if everything right.

That's it.

I'd like to know of other comparision too... with other low noise stuff.

Kind regards,
Max

[Max]

Hi Max, it's not AD.
Here is a picture of the device, looks old isn't it...?

Hi,
yes... it's old... it's a Thomson-CSF's metallic LF353... very old!

http://en.wikipedia.org/wiki/Thomson-CSF

Kind regards,
Max