Lrl from Italy

[FrancoItaly]

With 8mHZ crystal the distance is 3 meters. With 16MHz crystal the distance is shorter
The spot has small stones with nuggets.
I do not know what is happening, so I asked if anyone has tried to let me know

Has the 16 Mhz version been tuned on a harmonica? With this device the sensitivity is higher because the mixer has a higher efficiency. I don't think the oscillator frequency is very important, because the frequency on which the phenomenon acts is in the FM range. However, it may be that the sensor stage amplifies more at a lower frequency.

[Rubin]

[QUOTE=FrancoItaly;161517]Has the 16 Mhz version been tuned on a harmonica?

Correct!!
As you say the frequency is not important, but I think detector don't working if oscilator has crystal <4MHZ.
Anyway, I changed all the components in the alarm section with 10 led as a voltmeter. In this case it works better.
Maybe the first part of the preamplifier has more gain and the circuit can detect rocks with nuggets. The circuit now can detect ghost targets,in practice dont working on real targets. So the next time I try to put the gain on first section lower.
We see..

[Jeg]

[QUOTE=Rubin;161518]

Has the 16 Mhz version been tuned on a harmonica?

The circuit now can detect ghost targets,in practice dont working on real targets. So the next time I try to put the gain on first section lower.
We see..

Do you consider gold nuggets as ghost targets? You should realise that this device catches a physical effect and not metals. You are lucky if you catch GOLD nuggets and not iron. Sooner or later you will bumped on to something more valuable. :-)

[Rubin]

[QUOTE=Jeg;161519]

Do you consider gold nuggets as ghost targets? You should realise that this device catches a physical effect and not metals. You are lucky if you catch GOLD nuggets and not iron. Sooner or later you will bumped on to something more valuable. :-)

I'm not saying nuggets of gold , that's your conclusion
I said nuggets on metal stones unknown to me.
Therefore, the extracted soils can be detected as targets.
In this case maybe need a gain for reject any external parasitic signal as stones

[Jeg]

Sorry. Since yesterday i thought that you were talking about gold nuggets. So you can excuse my surprise

ps. Think again the second suggestion of Franco about a real target somewhere there before going for modifications.

[Rubin]

Sorry. Since yesterday i thought that you were talking about gold nuggets. So you can excuse my surprise

ps. Think again the second suggestion of Franco about a real target somewhere there before going for modifications.

No problem. I should have mentioned it from the beginning
Buried target tests have been performed, but in really "hard" soils, stones with nuggets can also be detected as targets.

[Jeg]

Thanks for sharing Rubin. I think it is difficult to avoid such cases no matter the frequency or the gain. If those soils are highly charged then receiver will be confused as all receivers i guess
which utilize electric field reception.

[JHERICKU]

Hi to all..To master Franci and friend Jeg..
My first attempt was not successfull so I decided to remake it based on the circuit I attached here.. can anyone review the circuit I made if there was mistakes on it..I made the power stage separated to sensor as master Franco stated..I don not have tupe C transistor so I used bc548b..
These were my observations:
1.1.853 volts without quartz on output..When I touched the antenna it increases to 3.911volts.
2.5.678volts with quartz on output and decreases when touched..
3.two leds were on,The first was steady and the second led qas blinking...Is this normal Franco?
4.The buzzer was annoying,it continuously beeping so loud and no way to lower it..
5.the voltage output was increasing when I touched the potentiometer knob..

What do you think Jeg?
ps.I used 4mhz quartz on 8mhz display one led..

[FrancoItaly]

If you read carefully the advice I gave for calibration, you see that without quartz the sensor stage DC output must be 0 V, otherwise self oscillation is present, and it is a condition to be avoided. The good news is that if there is self oscillation it means that the transistors have sufficient gain. Decrease C13 / C14, 330 pF or less, if not enough, increase R10 / R12, 1.2 K or 1.5 K.

[JHERICKU]

Thank you Franco..I will do ur advice..Is itnormal the leds are lighting?one was steady and the other one was blinking?I thought it only lights when there is a detection?

[Jeg]

Hey Jh
Also check in your diagram what i have in a red cycle. Are those points connected between each other as it should?
Check the green lines. It looks like your ground (-) connects to pins 2,3,4 while it needs to be attached only to 4.
I don't see something else. The rest of the circuit looks good.


After checking that you should follow what Franco wrote you above until you see zero volts at the output of sensor without crystal.

[FrancoItaly]

In the power stage the LED flashes when the supply voltage drops below 16V, and this is adjusted by means of the potentiometer P1. You can use a stabilized power supply instead of batteries and set it to 16V, then adjust P1 until the led starts flashing.

[JHERICKU]

Greeting to all especially to master franco..With potentiometers on max one led was on lights..when I placed my hand about 6 inches if turn off..when I toucehd the antenna..all leds will lights..
Any idea master?Thank u..

[FrancoItaly]

Greeting to all especially to master franco..With potentiometers on max one led was on lights..when I placed my hand about 6 inches if turn off..when I toucehd the antenna..all leds will lights..
Any idea master?Thank u..

As I have already said, the important thing is that by touching the antenna there is a change in signal, usually it is a decrease.

[ERDOGAN37]

https://www.youtube.com/watch?v=ZNoytV-mPKs