Lrl from Italy

[mustefa ubram]

hi franco
I've tested the sensor output with 3 -2-1 capacitor of 1p.(c2-c3-c4)

The output voltage for each of the different

with 3 capacitor:2.5v

with 2 capacitor:5v

with 1 capacitor:6.2v
Which is the best situation?

edited

[FrancoItaly]

In theory there is no difference because the gain does not change, but if you wanted to increase the gain you can use the 3 capacitors and then have 2.5V and increase C13 / C14 until you have about 5V, but it is better to increase the gain of display stage, especially to avoid self oscillations.

[dream_man]

Hello dear Franco;
As you mentioned earlier, after preparing the circuit, we must disconnect c2,c3 and c4 and measure the output voltage, it must be zero. Then you suggested using a 1pF cap instead of c2,c3 and c4 and measure the output voltage, if it is lower than 5 we must increase c13 and c14. What about high amplification and self oscillation If we increase c13 and c14 in order to obtain a greater amplification?,,, I mean, is there any bad side effect on this circuit if we increase c13 and c14 in order to have a 5 volt output?... which one is better, using 1 single 1pF or using three 1pF in series and increasing c13 and c14? .. sorry for this question

[FrancoItaly]

Hi dream man,

We have to have some gain in the sensor stage and this depends mainly on the amplification of TR2 / TR3 / TR4, unfortunately (unlike operational amplifiers) can not be established during the design phase, so we must act on C13 / C14 to get the correct gain. I recommend for this operation to disable the oscillator and to vary C13 / C14 for maximum gain (no self-oscillation).Once it has obtained the maximum gain you can find the right value for C2 / C3 / C4.

Best Regards

[dream_man]

Thank you Franco for replying;
but how to ensure that we have the maximum gain. after disconnecting c2,c3 and c4, what output voltage we must have in the TR5 emitter?
by increasing the C13 and 14 we increase the output voltage while quartz is disconnected. So the main question is finding the right value for c13 and 14. Please recommend a way to realize the right value.

[FrancoItaly]

Hi dream man,
while quartz is disconnected you must have in the TR5 output 0 volt. With quartz connected and c2,c3 and c4 disconnected you may have a few volts at output and this is a parasitic coupling and this is not negative (if the signal is stable and the sighal goes low by touching the antenna). On the contrary connect C2/C3/C4 for about 5 volt at output, however, it is not necessary to have at all costs 5 V, a lower gain at this stage may be offset by the display stage.

Best Regards

[dream_man]

Thank you dear Franco for your productive information;
I disconnected the quartz and increased C13 and C14 to 4.7nF (472 tag) and at this value I have 0.05 volt in the TR5 emitter. Then I connected the quartz and in place of C2 and C3 I replaced a 3pF and 27pF in series and got a total capacitance of 2.7pF. At this state, the TR5 emitter has a 4.85 volt. Is it correct that I configured those capacitors in series to get 2.7pF ? or this value is high?... whats your suggestion if any? ... thank you in advance dear Franco.

[FrancoItaly]

I think it's perfect, every installation is a special case, which depends on the tolerance of the components, especially the gain of the transistors and the parasitic capacitance of the PCB.
I also want to celebrate the thousandth post of this thread and I hope that many of you are able to build my LRL. I will add that with my LRL has been made a very, very important find.

[Napsterce]

Hello Franco, important find like a find in the circuit, or an important find like gold, silver... 😃😃

[dream_man]

Hello Franco...
Really fantastic... after the changes I've mentioned above, I tested the circuit at home. Surprisingly, I got one LED on near refrigerator and I thought that is because of its electricity wire but it was not. After that I've opened the refrigerator's door and after a while when the air came out all 3 LEDs turned on. I think the weather inside the refrigerator is ionized and circuit catchs it. It's great Franco. At least for me it responds.

[mustefa ubram]

hi franco
This is my specifications of the device:
antenna:50cm
out put voltage sensor :about 5 volt
L=3turn
c=22p & variable Capacitor
test point:100 grams of silver at a depth of 25 cm About 1 month in the soil.
I've tested in practice.Unfortunately, in practice, had no answer.
what is your opinion?

[brs]

One month is not enough after three months

[FrancoItaly]

Hi mustefa,
what kind of silver? maybe you need to wait any longer, as brs says.

[mustefa ubram]

Hi mustefa,
what kind of silver? maybe you need to wait any longer, as brs says.

25pcs coin silver historical ...

[folharin]

someone test this LRL real testing ground , which result?