After zeroing, the search depth became worse!?

[Ravensouth]

In the beginning I measured directly at the RX coil and zeroed it to 0.01V. Later I learned that I need to measure the pin 7 at the LF353 to zero correctly. With the LF353 I came to a value of 560mV. Before I zeroed in the LF353, my search depth was 32cm, with a 1 euro coin. Now she is maybe 10cm and 15cm with a hammer. Can it be due to the high tolerance of my multimeter? With the Oszi, the zeroing would be more accurate, but I have none available. The batteries in the multimeter I have changed for safety's sake. The batteries for my circuit (8x1,5V batteries) would still be full (12,14V according to my multimeter). How do I get the zeroing right? Did I do something wrong?

Best regards
Raven

[kt315]

i had noticed if i answer then George and Carl begin answer after me. why not BEFORE me??
do your comments and do not wait my comments.

Did I do something wrong?
---
yup. sure wrong because there is not details procedure 'how-to-make'. whites, tesoro, first texas specialists are keeping
all techniks in deep secret. FIRM SECRET.

ok. you have to have oscilloscope. russians use a half or 1/4 of kopeika (kopeika is old Soviet coin, in USSR hard era, we call that time THE REAL SOCIALIZM).
first stage you must balance your coil as minimum as you have to have. certainly you look on preamp output.
second stage, you must sure balance your coil in MICROVOLTS. that doind by MOVING the kopeika piece in different directions
in a space RX - TX. you get absolute minimal voltage with some phase. MICROVOLTS.
fix it with transparent glue.
take a piece of ferrite in hand and move on coil. its like a ground. must be no reaction.
take a coin. you see ...
take a ferrous. you see ...

[Qiaozhi]

i had noticed if i answer then George and Carl begin answer after me. why not BEFORE me??
do your comments and do not wait my comments.

It's because Ravensouth made his post at 6:30am (UK time), and you posted your reply 16 minutes later. Also, Lithuania is in a time zone that is 2 hours ahead of the UK, and 9 or 10 hours ahead for Carl (depending whether he's in Texas or Oregon).

In the beginning I measured directly at the RX coil and zeroed it to 0.01V. Later I learned that I need to measure the pin 7 at the LF353 to zero correctly. With the LF353 I came to a value of 560mV. Before I zeroed in the LF353, my search depth was 32cm, with a 1 euro coin. Now she is maybe 10cm and 15cm with a hammer. Can it be due to the high tolerance of my multimeter? With the Oszi, the zeroing would be more accurate, but I have none available. The batteries in the multimeter I have changed for safety's sake. The batteries for my circuit (8x1,5V batteries) would still be full (12,14V according to my multimeter). How do I get the zeroing right? Did I do something wrong?

Best regards
Raven

You should not attempt to null your coils to zero. There needs to be a phase-offset appropriate to the design. In the case of the TGSL, it's needs to be around 20 degrees. Yes, you need an oscilloscope to do this properly.

[Ravensouth]

Could you recommend a cheap Oscilloscope . Without oscilloscopes, I probably can not get on with the TGSL

[Qiaozhi]

Could you recommend a cheap Oscilloscope . Without oscilloscopes, I probably can not get on with the TGSL

Opinions vary, but IMHO you will need an oscilloscope with a minimum of 10MHz bandwidth and 2 channels.
You should be able to pick up an analog scope secondhand at a cheap price. However, if you want to continue in electronics, it would be worth the investment to get yourself a more modern digital scope. Many people here have bought Rigol scopes, which appear to be really good value. Personally I use a GwInstek GDS-1022 that I've owned for a number of years. There are also Hantek scopes to consider.

https://www.rigol-uk.co.uk/Digital-Oscilloscopes-s/1826.htm
https://www.amazon.co.uk/Rigol-DS1052E-Digital-Oscilloscope-Bandwidth/dp/B005ZPGPI6/ref=sr_1_5?keywords=rigol+oscilloscope&qid=1569489 748&sr=8-5
https://www.gwinstek.com/en-global/p.../Oscilloscopes
https://www.amazon.co.uk/Hantek-DSO5...9489748&sr=8-4

Some people here also use PC-based scopes, but I cannot comment on these, having never used one.

[ivconic]

Could you recommend a cheap Oscilloscope . Without oscilloscopes, I probably can not get on with the TGSL

Oh yes you can!
First 20-30 coils for TGSL i "balanced" without scope and without any kind of instrument.
I had 2 channel scope at the time too, i was very lazy to annoy myself with it.
Why annoyance when it is doable fast and easy in just few steps.
Using only 1 Euro coin and small piece of ferrite.
It is trial & error method. Giving very good results after twenty minutes of efforts.
Move coils a bit, try with euro, try with ferrite. See what happens. Repeat. Repeat. Repeat until you get satisfactory results.
A bit of patience and there you did it.
I never actually had real need to change that method... until folks from forum started to annoy me much with questions how to do it.
To look more "profound" and "conversant"; i started to talk scopes and instruments... just to be compatible with forum yoyos.
With that method you can get pretty nice "balanced" coil and all you have to do later is just to fix it good with some resin or glue.
That's the naked truth.
Take it or leave it, whatever.

[ivconic]

Be aware and do keep in mind that there are places and areas at home where is impossible to balance coils, at all.
Due presence of various artificial ac em fields.
I did truly splendid coils in my old workshop. And later when i moved to another room; it was impossible for me to make any coil good.
Until i discovered the source of all the troubles.
I have a friend who tried for months to make proper coil. It was impossible in his house. We discovered that later.
That's the fact that nobody will emphasize or tell you.
So, first make sure that your workshop is in the "right" room of your home!

[ivconic]

Slightly of topic... but can be helpful a lot.
Once i made my first "Ivconic Zahori" and start "exploring" the rooms in my house; i was scared and amazed, both at the same time, to see the real picture and situation on these matters.
I literally "drawn" a precise "schematic" of areas at home where is impossible to balance any coil.
It becomes clear to me why i couldn't manage to make any proper coil in my new workshop.
So i decided to move back my workshop to old room, where it was before.
With huge risk to be damned forever by my wife.
Point is; is advisable to have any kind of similar instrument that can detect and measure spreading of artificial ac em fields at home.
Various households and appliances can be horrific source of real ac magnetic "storms" at home.
Usually we are totally unaware in what conditions we are living on.
Making good coils would be most trivial reason to move you to explore better your living place.

[ivconic]

Man never learns enough.
Yesterday i discovered that damn flashing 5mm led diode (i put on my diy guitar amp, to make it "fancy") is totally destroying FM reception on my radio.
Damn flashing diode! Must have some wild oscillator inside?
Yesterday i salvaged vintage Pioneer TX-720 tuner and was very happy to see how mighty it is in fine reception of the most distant stations.
It is made in 1981. I haven't seen anything better than that so far, relating to sensitivity and finest reception.
Coincidentally i switched diy guitar amp with that damn diode and Pioneer tuner died at once! All i got is perfect white noise from speakers.
Once i shut down the amp; tuner returned to life again. So!
Despite the fact that i used high quality RG58 copper shielded cable to connect it with outdoor antenna. Flashing led kills it anyway.
So.. damn led is going out!
Now after reading this story; you can only imagine what's happening with your coil balancing in case if you have any kind of similar hidden "enemy" there close to your workbench.

[Qiaozhi]

Oh yes you can!
First 20-30 coils for TGSL i "balanced" without scope and without any kind of instrument.
I had 2 channel scope at the time too, i was very lazy to annoy myself with it.
Why annoyance when it is doable fast and easy in just few steps.
Using only 1 Euro coin and small piece of ferrite.
It is trial & error method. Giving very good results after twenty minutes of efforts.
Move coils a bit, try with euro, try with ferrite. See what happens. Repeat. Repeat. Repeat until you get satisfactory results.
A bit of patience and there you did it.
I never actually had real need to change that method... until folks from forum started to annoy me much with questions how to do it.
To look more "profound" and "conversant"; i started to talk scopes and instruments... just to be compatible with forum yoyos.
With that method you can get pretty nice "balanced" coil and all you have to do later is just to fix it good with some resin or glue.
That's the naked truth.
Take it or leave it, whatever.

OK - Ivconic is correct. You can balance your coils without an oscilloscope, but it's not that simple to do.
Of course, it does help if you understand what's going on in the balancing process, and you have a mental picture of what's happening. Also, if you use a scope, you will see all the "noise" that Ivconic talks about in later posts.
In addition, fault finding a non-working design becomes much easier with a scope. No doubt you've read the many posts in these forums from people who are blindly changing components , or even totally rebuilding a design in a vain attempt to get a working unit. If you don't have a scope, it's analogous to having one hand tied behind your back.

However, if you don't understand how ground balance and discrimination work in the TGSL, then you're already in trouble.
There is no substitute for knowing what you're doing.

[ivconic]

OK - Ivconic is correct. You can balance your coils without an oscilloscope, but it's not that simple to do.
Of course, it does help if you understand what's going on in the balancing process, and you have a mental picture of what's happening. Also, if you use a scope, you will see all the "noise" that Ivconic talks about in later posts.
In addition, fault finding a non-working design becomes much easier with a scope. No doubt you've read the many posts in these forums from people who are blindly changing components , or even totally rebuilding a design in a vain attempt to get a working unit. If you don't have a scope, it's analogous to having one hand tied behind your back.

However, if you don't understand how ground balance and discrimination work in the TGSL, then you're already in trouble.
There is no substitute for knowing what you're doing.

"Mental picture" is my middle name!
Of course i agree with you Q. Completely truth.
I just wanted to tell a man that it is not end of the world because he couldn't manage to properly balance coil at first few attempts.
Balancing coils for VLF IB is most delicate part in whole process of making the detector.
It can be done without instruments though, in cases of simpler designs like TGSL is.
TGLS is having behavior that may be simplified to "go - no go" kinda explanation.
With two testing targets with quite opposite magnetic features, using logical thinking and deduction; pretty correct coil balancing can be done.
ON SIMPLER designs only, of course. I forgot to emphasize that.
But if we talk seriously; oscilloscope is mandatory. Of course.
Just for the reason you mentioned; you can also see the presence of interference too, using oscilloscope. Any possible hum too.
And with scope you can achieve pretty precise and tight balance too.
But since TGSL is simple and pretty tolerant design; more relaxed approach is good enough too.
...
I am buried deep into analyzing the case of flashing led diode now. Again i assumed wrong!
It is not the flashing diode; it is the D-class amplifier based on PMA chip! Sheeeesh!
Again; man never learns enough! So much from any "mental pictures"...

[kt315]

look on pic

[Qiaozhi]

look on pic

[ATTACH]47624[/ATTACH]

Anatolij - you will need to translate that for those ignorant of the Russian lingo.

[Ravensouth]

that's right

[Ravensouth]

At work we still have an oscilloscope left, which I will use tomorrow. It is believed to be a Tectronic. In any case, I will not find a trouble-free place in my flat as well as at work. I just have to try it with the oscilloscope. The zeros could be a bit problematic, since I had already fixed the coils with hot glue ... Oops ... well, maybe I'll get the glue off with a cutter knife. I also got a ferrite core. The balance I do with the ground or? Turn clockwise until the ferrite disappears? I could also send you pictures if necessary