Lrl from Italy

[mustefa ubram]

hi franco
Franco I corrected according to your guidance

[FrancoItaly]

It seems to me that it is fine, but the definitive proof is the good functioning. I must admit that it is not easy to set up, in this period I am working on a sensor stage of a lrl that I realized long ago, its sensitivity is low, while revealing the phenomenon. I think the reason is the low beta of the transistors but unfortunately where I am I don't have the possibility to try other transistors. I have yet to try removing R10 / C13 to get the maximum gain.

[sakher]

test frequncy

Hello my frinds
where is the best points on the circuit to test frequency?

[FrancoItaly]

If you mean the input frequency of the sensor stage you can only calculate it theoretically with the values of L1 / C10 + about 10pF of the parasitic capacitance of the TR2 base / emitter, or you can use an external oscillator and check for what frequency there is a variation to the out of the sensor stage. However the most important thing is to establish which is the best frequency on the test field, C10 can be 10 or 15 or 20pF, or nothing, only the base / emitter capacity.

[sakher]

If you mean the input frequency of the sensor stage you can only calculate it theoretically with the values of L1 / C10 + about 10pF of the parasitic capacitance of the TR2 base / emitter, or you can use an external oscillator and check for what frequency there is a variation to the out of the sensor stage. However the most important thing is to establish which is the best frequency on the test field, C10 can be 10 or 15 or 20pF, or nothing, only the base / emitter capacity.

Thank you Mr.Franco, Is there required frequency range that i must measure it ?

[FrancoItaly]

Thank you Mr.Franco, Is there required frequency range that i must measure it ?

There is no particular frequency required, it is just a matter of finding the best value for C10. I found that my lrl (in my country) also works well with L1 = 2 turns and C10 = 10pF, or L1 = 3 turns and C10 = 22pF. I think that the phenomenon emits in the range 80 - 120Mhz and that it is important that there are radio or TV stations that transmit in that frequency range that act as a "stimulus". This could explain why my lrl (but I also believe others) does not work in certain areas.

[sakher]

Thank you very much

[taher5739]

Hello dear franco
I have a question from you
Have you tried an antenna amplifier on the test field?
If your answer is yes What has Results?
Thanks for your patience.

[FrancoItaly]

Hello dear franco
I have a question from you
Have you tried an antenna amplifier on the test field?
If your answer is yes What has Results?
Thanks for your patience.

In my case the sensitivity has increased by about 20%. The main advantage is that the antenna amplifier compensates for the fact that the sensor stage has not been adjusted for the highest possible sensitivity.

[taher5739]

Sensitivity for gold or silver has increased, or both?
I want to know if adding the filter to the antenna amplifier section ,
Can make a distinction for copper or gold?
i wish you success in life

[havoc88]

Dear Franco which coil is right? or very sensivity

1. or 2. picture?

There is no "right" or "wrong" coil at least if both of them have three turns of wire plus there is no special reason to have vertical or horizontal position, only practical workspace on your pcb.

[k.hasanzade]

Dear franco
Thanks first for the design of the circuit that you design
I have a few questions
1. What is the reason for changing the circuit coil?
2. It is better not to install the first coil vertically and the second wire sheet horizontally؟
3.What is the new circuit calibration method?
best reguard
k.hasanzade

[FrancoItaly]

Sensitivity for gold or silver has increased, or both?
I want to know if adding the filter to the antenna amplifier section ,
Can make a distinction for copper or gold?
i wish you success in life

I buried silver and gold objects in my test field. Silver, buried for about 2 years, responds well, while gold, which has been buried for less than a year, responds little. In my previous test field (not here but in Italy and that I no longer have available) instead the gold responded well and it was a thin bracelet.
The amplifier antenna increases the sensitivity for all metals and I do not believe that the addition of a filter can be useful, however I did not do this test.

[FrancoItaly]

There is no "right" or "wrong" coil at least if both of them have three turns of wire plus there is no special reason to have vertical or horizontal position, only practical workspace on your pcb.

I agree, the coil is part of a resonant circuit and there is no risk of self-oscillation. In fact, if there were two coils belonging to two different stages and tuned to the same frequency, there would be this risk and placing the two coils perpendicular to each other would reduce mutual coupling.

[FrancoItaly]

Dear franco
Thanks first for the design of the circuit that you design
I have a few questions
1. What is the reason for changing the circuit coil?
2. It is better not to install the first coil vertically and the second wire sheet horizontally؟
3.What is the new circuit calibration method?
best reguard
k.hasanzade

I refer to the antenna amplifier not to the antenna amplifier 2 which I suggest to build after the antenna amplifier.

1. The amplifier antenna increases the signal received from the antenna (let's call it phenomenon) and increases the total gain of the sensor stage which in some realizations may not be sufficient.
2. With the addition of the amplifier antenna there is always only one coil which is only moved.
3. The calibration method remains the same, only you have to do so before mounting the antenna amplifier. Subsequently the amplifier antenna is mounted and on the test field the 4.7K trimmer is set for maximum sensitivity.