Lrl from Italy

[Pahom]

Originally Posted by Inna

Hi, anyone could tell me what is the correct value to consider when the battery is low in this project (8 Mhz) ? Perhaps 11 Volt is right or other values?
Thanks at all.

No, below 12 volts, it will lag. Even more or less normal operation depends on the layout of the board.

[FrancoItaly]

Originally Posted by Pahom

No, below 12 volts, it will lag. Even more or less normal operation depends on the layout of the board.

My lrl runs at +12V stabilized, 2x 9V batteries in series give 18V, I consider them discharged when the voltage drops to +15.5V, as the stabilizer IC must have at its input a voltage at least +3V higher than the output.

[Inna]

Apologize again, but I have another question: instead of 1 Megaohm, can I use a 470 K for potentiometer P2? Due to logistical problems related to the place where I am, I can't find a higher value. Do you think it can be work better like with 1 Mohm? Is it perhaps better to also insert a fixed 100/220 ohm resistor in series with p2?
Thanks again.

[FrancoItaly]

Originally Posted by Inna

Apologize again, but I have another question: instead of 1 Megaohm, can I use a 470 K for potentiometer P2? Due to logistical problems related to the place where I am, I can't find a higher value. Do you think it can be work better like with 1 Mohm? Is it perhaps better to also insert a fixed 100/220 ohm resistor in series with p2?
Thanks again.

You can put 470K in series with potentiometer, that way you can adjust the gain from half to full. Or you can use a 1M trimmer and adjust it for the greatest gain without having instability. Rarely do you adjust the gain, once you find the right value, also the gain can be decreased by lowering the threshold.

[Inna]

Yes, I wrote wrong, I meant 100/220 kohm. You have to excuse me, but I'm just an electronics hobbyist, so P2 adjusts the gain which, once adjusted, always remains the same, so it's possible not to take it out of the box and replace it with an internal trimmer. Then If I may ask again, what do the other 2 potentiometers regulate? To be clearer, Mr. Franco, I ask you, could you describe what to do with the device and how to adjust it for research, after turning it on? That is, on which potentiometers to intervene and how to start field research? In short, having a small user manual on plein-air...
Thanks for your patience.

[FrancoItaly]

Originally Posted by Inna

Yes, I wrote wrong, I meant 100/220 kohm. You have to excuse me, but I'm just an electronics hobbyist, so P2 adjusts the gain which, once adjusted, always remains the same, so it's possible not to take it out of the box and replace it with an internal trimmer. Then If I may ask again, what do the other 2 potentiometers regulate? To be clearer, Mr. Franco, I ask you, could you describe what to do with the device and how to adjust it for research, after turning it on? That is, on which potentiometers to intervene and how to start field research? In short, having a small user manual on plein-air...
Thanks for your patience.

In the original version there was only one potentiometer for threshold adjustment, later I added another one, so one is for fine tuning and the other for coarse tuning. You operate in the same way as a metal detector, adjust the gain, if any, for a stable threshold and then adjust the threshold, just below the point where the first LED lights up.

[omar]

Found this diagram on a site and it looks nice

[Inna]

Originally Posted by omar

Found this diagram on a site and it looks nice

Very good, the antenna amplifier and the battery monitor are missing, but that's not a problem. Could you kindly share the site from which to download the files, also to have the right sizes of the pcb.
Thank you.

[FrancoItaly]

Originally Posted by Inna

Very good, the antenna amplifier and the battery monitor are missing, but that's not a problem. Could you kindly share the site from which to download the files, also to have the right sizes of the pcb.
Thank you.

Thank you, it will be very useful for many forum members.

[Inna]

Does the last pcb version also include a variable condensator on the antenna input? This could be a good chance?

[omar]

https://top4top.io/downloadf-2530spk8i0-rar.html

[FrancoItaly]

Originally Posted by Inna

Does the last pcb version also include a variable condensator on the antenna input? This could be a good chance?

A variable condenser on the antenna input can be useful in the 20Mhz version where a 20Mhz crystal is used and the antenna circuit is tuned on a harmonic of the oscillator, it can be 80 or 100Mhz. With 8Mhz quartz the harmonics have too small amplitude. However, with the 8 Mhz version, you can try to adjust the capacitor to look for a point where the DC output signal increases, possibly putting a 22pF capacitor in parallel with the variable capacitor.

[Inna]

Originally Posted by FrancoItaly

A variable condenser on the antenna input can be useful in the 20Mhz version where a 20Mhz crystal is used and the antenna circuit is tuned on a harmonic of the oscillator, it can be 80 or 100Mhz. With 8Mhz quartz the harmonics have too small amplitude. However, with the 8 Mhz version, you can try to adjust the capacitor to look for a point where the DC output signal increases, possibly putting a 22pF capacitor in parallel with the variable capacitor.

A variable capacitor like these?

[FrancoItaly]

Originally Posted by Inna

A variable capacitor like these?

Yes, 50pF is ok.

[Inna]

Originally Posted by FrancoItaly

Yes, 50pF is ok.

Thanks! Always there to help. Great Mr. Franco.

[Inna]

Sorry again, but on this pcb posted by Omar, I can't find the solder point for the antenna. Capacitor values ​​are not written. With a little patience they can be deduced, even if at sight, they seem much more than those in the original scheme. Instead in the point that I highlighted with an orange circle, I can't figure out what should be connected to it.

[omar]

Dear, the point you marked with a circle. It is the measuring point of the sensor output.

I will use my friend to write down the missing values

[Inna]

Originally Posted by omar

Dear, the point you marked with a circle. It is the measuring point of the sensor output.

I will use my friend to write down the missing values

Thanks Omar, please could you ask even where is the antenna point?

[omar]

[Inna]

Originally Posted by omar

Great! Well done Omar!

[rxlock2]

can someone put the PCB in PDF for printing

[FrancoItaly]

Originally Posted by rxlock2

can someone put the PCB in PDF for printing

Of course you have to reduce the size.

[rxlock2]

Originally Posted by FrancoItaly

Of course you have to reduce the size.

Thanks a lot, but I mean the PCB in PDF format to make it a board

[Pahom]

Originally Posted by rxlock2

Thanks a lot, but I mean the PCB in PDF format to make it a board

This board is in Laot, the link is in the posts above. If you can not download the link, I can send you a personal mail.

[rxlock2]

Originally Posted by Pahom

This board is in Laot, the link is in the posts above. If you can not download the link, I can send you a personal mail.

I don't want a file in lay format, but in PDF format like in the photo so I can print it
mail: rxlock2@gmail.com
Τhanks.