Lrl from Italy

[FrancoItaly]

self oscillating sensor stage.

This new version should be more sensitive than the original one, although it is simpler, unfortunately I have no possibility at the time of doing field tests. Briefly, it's about bringing the sensor stage into self oscillating (in my case about 15 Mhz) and regulating L1 / C1 on a harmonic. This will increase the sensitivity. The setup is different from the other version, in fact here we want the self oscillating of the stage and not avoid it.
Let's see what are the differences from the original version:
- there is no quartz oscillator.
- there are no resistors and capacitors
of emitter, to have the maximum
gain.
- In parallel to L1 there is a capacitor
variable instead of a fixed one.
Self oscillation depends on the following factors:
- the gain of the transistors,
those of type BC ... C are required.
- the value of C3 and C4.
- the drawing of the pcb.
Since this lrl derives from the previous one and is simpler, you can use the same pcb, even the setup is simpler:
Adjust C1 until a voltage in the range 2 - 5 V is obtained at the output of the sensor stage. If the output is> 5V then decrease C3 or C4. If the output is zero, then increase C3 or C4.
Also with this lrl touch the antenna with your hand and check that the signal decreases.

[FrancoItaly]

I must warn you that this version does not detect the phenomenon or at least in a point of my land where my other lrls give a signal. Maybe L / C1 is tuned to too low a frequency, I'll make some tweaks and then let you know.

[brain]

I must warn you that this version does not detect the phenomenon or at least in a point of my land where my other lrls give a signal. Maybe L / C1 is tuned to too low a frequency, I'll make some tweaks and then let you know.

Did you use s9014 transistor? DC current gain hfe value min 60 max 1000

[FrancoItaly]

Did you use s9014 transistor? DC current gain hfe value min 60 max 1000

I use BC183C, gain in the range 500 - 800, but the probleme is not the transistors.
Probably the frequency of L1 / C1 = about 40 pF is too low to detect the phenomenon, at least in my area. I want to try to trigger the oscillation by connecting the collector of TR3 directly with L1 / C1 through a capacitor (few pF) and instead of C1 a capacitor of 22 pF.

[brain]

huge difference .signal gets too sensitive .

[AurumKid]

This design and circuit of Mr. Franco, which has been slightly strengthened by our good friends, and of course it is much better to increase the distance of the sensor from the discipline. However, it is very powerful and sensitive.

hello sir can you share your complete files for this project. i want to try this.

[FrancoItaly]

hello sir can you share your complete files for this project. i want to try this.

I advise you to make the original project first, which is certainly working, while the later versions as far as I'm concerned are not stable or do not work in the field, but currently I do not have a test field but only an area where the original lrl provides a good signal.

[FrancoItaly]

I place the new display stage that allows a better adjustment of the threshold and the power stage, alternatively you can use any stabilized power supply.

[AurumKid]

thank you sir for your kind support i will start collecting all parts needed to build the 8Mhz circuit.

[AurumKid]

is it ok to add digital VU meter to the circuit or is there any available circiut with VU meter in this thread forum?

[FrancoItaly]

is it ok to add digital VU meter to the circuit or is there any available circiut with VU meter in this thread forum?

It is possible to use digital VU meters, however it is more complicated to put a buzzer and adjust the threshold, in my opinion 3 LEDs are more practical. However, other LEDs can be added.

[liudengyuand]

Must use metal casing

[liudengyuand]

So far, I have made a silver coin with a diameter of 4cm can reach a detection distance of up to 100, but its depth is only tens of centimeters, which is far lower than my depth requirement. I don?t know how your detection depth is, whether there is Tested?

[FrancoItaly]

So far, I have made a silver coin with a diameter of 4cm can reach a detection distance of up to 100, but its depth is only tens of centimeters, which is far lower than my depth requirement. I don?t know how your detection depth is, whether there is Tested?

Do you mean 100m?

[liudengyuand]

yes