Lrl from Italy

[kiro077]

For C2-C3-C3 I used the parasitic capacitance of the board. For C13-C14 (470pf). I use one printed circuit board for the whole lrl.

[FrancoItaly]

Originally Posted by kiro077

For C2-C3-C3 I used the parasitic capacitance of the board. For C13-C14 (470pf). I use one printed circuit board for the whole lrl.

As I told you, a PCB just for the sensor stage, with the bottom face connected to ground, makes a higher gain possible.

[FrancoItaly]

Originally Posted by FrancoItaly

As I told you, a PCB just for the sensor stage, with the bottom face connected to ground, makes a higher gain possible.

If there are many electromagnetic disturbances inside the house it is better to calibrate outside, also remember that the antenna must be connected during these operations, I recommend extending it to about 40cm.

[kiro077]

If I shield the box, will it get more amplification?

[FrancoItaly]

Originally Posted by kiro077

If I shield the box, will it get more amplification?

it is possible, in fact the body participates in the detection process, holding it with two hands the gain increases compared to holding it with just one hand, furthermore the lrl remains less sensitive to disturbances, it must be shielded (with aluminium foil, including the handle).

[osman34]

Originally Posted by omar

Yes, my friend Othman, there is a problem. Correct the location of the 33 nano capacitor connected to the 4148 signal correction diodes...


Note: Try the device with or without the protection diode on the voltage input and choose the best.

Merhaba Omer, I disabled the diode. I made a direct connection. How should I correct the positions of the 33 nano capacities?

[omar]

[FrancoItaly]

Originally Posted by omar

Both diodes are needed, they constitute a full wave rectifier, since silicon diodes have a conduction threshold of about 0.7V and signals lower than this threshold are blocked. However, this is not a problem since the signals are of higher amplitude.

[osman34]

Omer, first of all, thank you. I corrected the mistake I made. I am operating it with DC 18V supply, the buzzer is constantly beeping. The adjustable resistor only lights up the first Yellow LED and then the Blue LED. The Green LED close to the 7812 Regulator does not light up at all. I need to pay a little more attention.

[osman34]

Originally Posted by osman34

Omer, first of all thank you. I have corrected the mistake I made. I am operating it with DC 18V supply, the buzzer is beeping continuously. The adjustable resistance only lights up the first Yellow LED, then the Blue LED and the Green LED. When I touch the antenna point I do not get any response. Do you have any idea where I should check?

.

[okantex]

Dear osman34
How is istanbul?

Probably you have problem with your second lm358
Since first LED works, you should have Signal at entrance leg3 of second lm358. But both leds are not works..seems problem is on lm358.
Maybe burned..or maybe miss connection..check solderimg.

[mc_307]

Hello Mr. Franko. I have a question about the settings of c13, c14 and c2-3-4. First we remove the crystal. Then we decrease the value of c13 until the emitter Tr3 oscillates. We increase the value of c13 a little and leave it like that and it does not oscillate. Do we also need to measure the emitter Tr4 for C14? After adjusting c13 and c14 we measure the emitter Tr5 and adjust the voltage from c234.

[FrancoItaly]

All measurements are made on the TR5 emitter and are a continuous voltage. Increasing C13/C14 increases the gain, therefore the output voltage, to avoid self oscillation you must decrease C13/C14. C2/C3/C4 are only used to fix the output voltage to a correct value.

[mc_307]

Originally Posted by FrancoItaly

All measurements are made on the TR5 emitter and are a continuous voltage. Increasing C13/C14 increases the gain, therefore the output voltage, to avoid self oscillation you must decrease C13/C14. C2/C3/C4 are only used to fix the output voltage to a correct value.

This is where things get difficult. For example, does the value of c13 affect the value of c14? If so, how much we need to change c13 or 14 remains unclear.

[FrancoItaly]

You can change only C13 first, if the value (greater than 10nF) is not enough also increase C14. Otherwise (if acting on C13/C14 is not enough) vary R10/R12, decreasing the value increases the gain. R10/C13 and R12/C14 are two high pass filters. In a later version of the lrl I put two trimmers in place of R10/R12.

[walkman]

Thank you very much for your guidance Mr. Franco.
It detects the lighter test very easily with a distance of 4m and a 20cm long antenna. I haven't been able to do a field test outside yet.

[electroaf]

good evening I am a new researcher in the LRL field I like your project I want to build this LRL but I want to know what is the resonance frequency of the system

[FrancoItaly]

My lrl is of the passive type as I think almost all the others are. The internal oscillator is only used to provide a reference signal, the reception frequency is determined by L1/C10 and is in the range of about 90/120Mhz. The most sensitive type is the one where L1/C10 is tuned to a harmonic of the quartz oscillator, the quartz frequency is 20Mhz but it is quite critical to realize. Of 3 20Mhz lrls made by me only one works well. I must warn that it is not easy to set up my lrl (even 8Mhz version) because of the very high gain it could easily self oscillate, if the gain is reduced too much it would be too insensitive, I recommend a single pcb for the sensor stage, of the double-sided type, with the lower face connected to ground and therefore with the components soldered on the upper part, without drilling the pcb.

[FrancoItaly]

My lrl was originally a self-oscillating rf sniffer that also worked as an lrl. Since it was critical to make, I added a quartz oscillator. For those making the 3-led version, I say to use the power supply stage of the 1-led version (in fact, it is not shown in the diagram). Power is provided by two 9V batteries in series.

[mc_307]

hello mr. franko. what happens if the value of the c10 capacitor is close to zero? can you give an example about changing the value of the c9 and c10 capacitors here? for example, what happens if the value of c9 is decreased? or what happens if it is increased. the same questions apply to c10. i wonder how the c9 and c10 capacitors affect each other. it is buried but i don't know what is inside, when the c10 capacitor is very low, i can only detect it when it is on it and from one direction. i want to increase this low value. does it make sense to change the value of the c9 capacitor for this?

[FrancoItaly]

Changing C9 is not needed, it serves to connect the filter to the TR2 base and its impedance to the frequency of the filter is very low, negligible. C10 determines the filter resonance frequency together with L1, put a variable capacitor (10/47pf) in place. If you do not put C10, however, the parasitic capacity of the basic/emitting junction of TR2 (about 7pf) remains.

[mc_307]

Hello Mr. Franko. I receive signals from 2 different places underground. One of them receives only in the west direction and slightly turned to the south. The other receives from almost 4 directions. However, it only detects when I come to it. There is no remote sensing. Do you have any advice regarding the remote sensing of the device? Which parts on the circuit are related to the remote sensing distance?

[FrancoItaly]

My lrl, like the others (except for modified metal detectors like Alonzo's pistol), works only as remote sensing and for metals buried for a long time. Anomalies in detection can depend on the type of soil, metal, burial time. We know little about the phenomenon that according to official science does not exist. The advice I can give is to do tests in the test field and try to understand how it works.

[abdou2014]

Hi Dear Franco , I hope you are well, I managed to find a lot of non-ferrous metals underground with your LRL, and I tried to increase the location distance by increasing the sensitivity, except that there is the effect of the sky and compass which is imposed,
Do you have a precise idea about the sky effect? ​​What exactly is it ?

[FrancoItaly]

I can't give you an answer, we know very little about the phenomenon, regarding the compass effect the Earth's magnetic field is undoubtedly important and for the sky the effect could be due to the electrostatic potential which increases as the height from the ground increases.