Lrl from Italy

[Jeg]

Hi Franco
Do you remember what is the pk-pk voltage value of the composite signal that reaches the base of Tr2? I mean about the product of mixing especially when we hit the right harmonic across the LC tank. Approximately.

Thanks in advance
Merry Christmass and happy new year to all.

[FrancoItaly]

Originally Posted by Jeg

Hi Franco
Do you remember what is the pk-pk voltage value of the composite signal that reaches the base of Tr2? I mean about the product of mixing especially when we hit the right harmonic across the LC tank. Approximately.

Thanks in advance
Merry Christmass and happy new year to all.

The value is very small, I don't think it's possible to measure it. The only reliable measurement is the sensor stage DC output and all changes in component values are made solely by observing the changes in the output voltage.

[Jeg]

Thank you Franco. I ll give it a try! :-)

[Jeg]

Hi all
Hi Franco

The input P1 trimmer seems that doesn't serve the purpose of its use. I tested two crystals 4M and 16M. The signal at the input of tr2 can not be less than about 50 mV. Imho, your initial design with many 1pf caps in series is a better approach for to increase impedance.

A second issue is the input tank coil. More turns than 3 will give higher sensitivity and higher Q. I made a coil of 8T on a 6mm former to test.

I'd like to ask if you have tested 90 degrees different orientation of the input tank coil than what you currently use. In other words, the coil on your board looks at the sides. Have you tested the operation when it looks forward?

Regards

[FrancoItaly]

Originally Posted by Jeg

Hi all
Hi Franco

The input P1 trimmer seems that doesn't serve the purpose of its use. I tested two crystals 4M and 16M. The signal at the input of tr2 can not be less than about 50 mV. Imho, your initial design with many 1pf caps in series is a better approach for to increase impedance.

A second issue is the input tank coil. More turns than 3 will give higher sensitivity and higher Q. I made a coil of 8T on a 6mm former to test.

I'd like to ask if you have tested 90 degrees different orientation of the input tank coil than what you currently use. In other words, the coil on your board looks at the sides. Have you tested the operation when it looks forward?

Regards

The signal at input TR2 is much smaller than 50mV, consider that the sensor stage is composed of transistors with a gain (direct current) of over 500 each, so the maximum gain is 500X500X500 and the stage would be in saturation without amplifying. I added the trimmer to better adjust the signal to base on TR2 and I found no difference between the two modes. I tried to increase and decrease the number of turns, the lrl only worked with 2 or 3 turns. You have to consider that it is a resonant circuit and increasing the turns decreases the frequency. In the 20 Mhz or 14 Mhz version the L / C is varied to tune on a harmonic of the oscillator and increase the efficiency of the TR2 mixer. Regarding the position of L1 I have not found any difference.

[Jeg]

Hi Franco

Thanks for the answer. What about if a commercial fm station transmits on the same frequency like your tuned input? Will your system saturate?

[FrancoItaly]

Originally Posted by Jeg

Hi Franco

Thanks for the answer. What about if a commercial fm station transmits on the same frequency like your tuned input? Will your system saturate?

Near the FM transmitters, a few hundred meters, the lrl is useless, too many false signals.

[Jeg]

Very useful notice tnks.

[Jeg]

Hi Franco
Just to tell you that your circuit is amazing. Great technique, and to mention that sensor circuit doesn't need any modifications at all!

Adjusted as to give me 1200mV at the output of sensor. Starts decreasing as i approach my hand close to the antenna at 40cm. When i finally touch it, it goes as down as 950mV. Almost 300mV decrement. Really great Franco. Thanks a lot. Its time for the indication stage.

ps. I solved my issue at the input. The increased oscillator's signal across the tank circuit was due to capacitive coupling. It came at the right levels when i isolated oscillator in a faraday type cage.

[FrancoItaly]

Originally Posted by Jeg

Hi Franco
Just to tell you that your circuit is amazing. Great technique, and to mention that sensor circuit doesn't need any modifications at all!

Adjusted as to give me 1200mV at the output of sensor. Starts decreasing as i approach my hand close to the antenna at 40cm. When i finally touch it, it goes as down as 950mV. Almost 300mV decrement. Really great Franco. Thanks a lot. Its time for the indication stage.

ps. I solved my issue at the input. The increased oscillator's signal across the tank circuit was due to capacitive coupling. It came at the right levels when i isolated oscillator in a faraday type cage.

I am happy that you have succeeded in the realization, of course the final and field testing. in the past I have also recommended shielding the entire box, including the handle, with grounded aluminum foil.

[Jeg]

Originally Posted by FrancoItaly

I have also recommended shielding the entire box, including the handle, with grounded aluminum foil.

For sure it would contribute in to a more clean amplification of the effect, but if inside the box is not taken in consideration the interaction between oscillator and the rest of the device there would be no way for setting the input level at minimums (due to capacitive coupling). I used a 16Mhz crystal by the way. No stability problems and clean signalling. Tuned to 32Mhz.

[brain]

I think I detected the iron frequency 68,490 khz.

[Pahom]

Originally Posted by brain

I think I detected the iron frequency 68,490 khz.

What device did you do it

[kostas87]

Hello Franco !
we have made the original version, we replaced the coil 3 turns with tsok ferrite. I think it goes quite well at 2 maybe 1 meter from a buried object with a phenomenon..the setting is very marginal just before the last led hits and when I turn it to the sky it hits gently..I detect with a slight inclination to the ground. do you think this is a normal function?

[JHERICKU]

I am busy on a lrl working with a PIR
Good wishs for you and all[/QUOTE]

Hello sir..can u update about this project using pir on lrl..Thank u..

[FrancoItaly]

Originally Posted by kostas87

Hello Franco !
we have made the original version, we replaced the coil 3 turns with tsok ferrite. I think it goes quite well at 2 maybe 1 meter from a buried object with a phenomenon..the setting is very marginal just before the last led hits and when I turn it to the sky it hits gently..I detect with a slight inclination to the ground. do you think this is a normal function?

The operation is not correct, in the absence of a phenomenon the lrl must remain silent, however it is tilted. I don't think it is not a good idea to use a ferrite since we are in the FM range, around 100 Mhz, normal ferrites do not reach these frequencies.

[JHERICKU]

Hello Franco..I sent a private Message..this was regards to the partslist of your original lrl..I cannot visibly read the values especially ic1 and diodes..Thank u..

[kostas87]

Originally Posted by FrancoItaly

The operation is not correct, in the absence of a phenomenon the lrl must remain silent, however it is tilted. I don't think it is not a good idea to use a ferrite since we are in the FM range, around 100 Mhz, normal ferrites do not reach these frequencies.

when there is no phenomenon there is no signal, you did not understand me..detects normally the phenomenon with very strong signals very close 1-2 meters when there is no problem when my direction is from north to south..but when I raise the antenna in the sky there is a signal from the sky..I make sure to adjust the device and have a signal up to the horizontal position.then I lower the device a little to the ground and the signal stops and I walk when I encounter a phenomenon the device emits a signal .. there is no signal continuously. ... basically I try to find the signals from the sky when they are connected to the earth ...

[FrancoItaly]

Originally Posted by kostas87

when there is no phenomenon there is no signal, you did not understand me..detects normally the phenomenon with very strong signals very close 1-2 meters when there is no problem when my direction is from north to south..but when I raise the antenna in the sky there is a signal from the sky..I make sure to adjust the device and have a signal up to the horizontal position.then I lower the device a little to the ground and the signal stops and I walk when I encounter a phenomenon the device emits a signal .. there is no signal continuously. ... basically I try to find the signals from the sky when they are connected to the earth ...

Usually the sky effect and the compass effect appear when there is too much amplification.

[FrancoItaly]

I put the original lrl again, as it was privately requested.

[JHERICKU]

Hello franco..Any idea about pcb e schema made by Dream man..is it ok to use?Thankbu in advance..

[mustefa ubram]

PCB FOR 20MHZ SENSOR

[FrancoItaly]

Good work, Mustefa

[JHERICKU]

Originally Posted by liudengyuand

Because of the machine, I got a huge wealth, I detected a lot of gold and silver and bronze, if you haven't succeed in doing, you can ask me why, I will guide you how to adjust

Hi liudengyuand..how did u made the curicuit effective?can u tell us more..

[Jeg]

Originally Posted by JHERICKU

Hi liudengyuand..how did u made the curicuit effective?can u tell us more..

Hey Jhericku
The circuit is effective by itself. Franco designed it very nicely. You don't need to change anything. It confirmed that detects only noble metals and no iron! Mine, it also can not detect copper


Just tune it to a harmonic that gives a nice output and you are there. Location distance not more than 4-6 meters. Works every day no matter the conditions. It is just that depending on the day, the field sometimes is weaker but still detectable.


If anyone likes to go deeper on this, then i suggest you to use a simple voltmeter instead of leds.


ps. I use a 16MHz crystal by the way. No stability problems.