Lrl from Italy

[Inna]

Hello to all this wonderful forum, I've just joined and I'm starting to make the project at 8MHz.
Meanwhile, a special thanks to Mr. Franco, a great person.
I would like to ask him or anyone who can kindly answer me: since this project has been modified by several people,
I can't figure out, for example, how many potentiometers there are to adjust outside the box, what values they have and
where to connect them on the pcb. I specify that I made the Walkman pcb, the last one above, but I don't know if it's updated enough
to the various changes (for example there'nt the low battery control) but it is'nt a problem. Is there anyone who has an complete overall scheme or diagram

where it is possible to distinguish which are the potentiometers and which are the trimmers and how correct use in field search.
Thank you all.

[FrancoItaly]

Hello to all this wonderful forum, I've just joined and I'm starting to make the project at 8MHz.
Meanwhile, a special thanks to Mr. Franco, a great person.
I would like to ask him or anyone who can kindly answer me: since this project has been modified by several people,
I can't figure out, for example, how many potentiometers there are to adjust outside the box, what values they have and
where to connect them on the pcb. I specify that I made the Walkman pcb, the last one above, but I don't know if it's updated enough
to the various changes (for example there'nt the low battery control) but it is'nt a problem. Is there anyone who has an complete overall scheme or diagram

where it is possible to distinguish which are the potentiometers and which are the trimmers and how correct use in field search.
Thank you all.

I post again the original lrl, modified with two pots for tuning and one for gain. The power supply stage with low battery is the one in the version with one LED, in the version with 3 LEDs it is not indicated but that of the 1 LED version must be used. The low battery regulation is a trimmer.

[Inna]

Dear Mr. Franco, I'm Italian and I would really liked to meet you in person because until a few years ago I lived in Genoa. But now unfortunately I find myself very far from Liguria. Besides, even my name is "Franco". I apologize again because I don't have a lot of experience in electronics, I'm a self-taught hobbyist. So if I choose to insert the new display stage, the external adjustment potentiometers would be: P1 of 47k. P2 of 1 Mega, P3 of 10k, it is right? Instead the power stage remains common for both versions and the antenna amplifier has a 4k7 trimmer. I would very much like to be able to write to you privately, but I'm not sure how to do it. Thank you for your great availability and kindness, as I have been able to see in this forum even with non-grateful people.

[FrancoItaly]

Dear Mr. Franco, I'm Italian and I would really liked to meet you in person because until a few years ago I lived in Genoa. But now unfortunately I find myself very far from Liguria. Besides, even my name is "Franco". I apologize again because I don't have a lot of experience in electronics, I'm a self-taught hobbyist. So if I choose to insert the new display stage, the external adjustment potentiometers would be: P1 of 47k. P2 of 1 Mega, P3 of 10k, it is right? Instead the power stage remains common for both versions and the antenna amplifier has a 4k7 trimmer. I would very much like to be able to write to you privately, but I'm not sure how to do it. Thank you for your great availability and kindness, as I have been able to see in this forum even with non-grateful people.

I sent you a private message, potentiometers are ok.

[Dubulumach]

Hello FrancoItaly and all

There is one optimal frequency 115.674 MHz and two variants of HC-49U quartz crystals.
1st. 115.5278 MHz main freq.
2nd. Overtone quartz 10.695 MHz or 10.700 MHz both are near geometric mean of main LC resonant tanl circuit.
L1 3 turns, wire diameter 1mm, 1.09mm enamelled, at 10 mm coil form, 10.5 mm lenght of coil with 3mm winding pitch.
Primary inductance 0.086 uH or 86 nH
Series resistance - 2.304 mOhm
Parallel resistance - 38.14 KOhm
Parallel capacitance Cs - 0.338 pico
Self resonant freq Fsr is very high 1.0895 GHz, wit Q-factor 619 and ESR 0.1 Ohm at 115.674 MHz
Together wit C10 ~ 22 pico, -3dB(Δf) bandwidth of parallel tank-circuit L1C10 is 302.5 KHz, Z= 63 Ohm and eq.resistance is Req = 21.93 KOhm.
Very probably LRL range is somewhere plus or minus 5Mhz from main oscillating LC tank-circuit freq. It should be from 110.5Mhz - 120.5 MHz. Phenomenon is very complex and no one living could explain it. It's all matter of experiments.

Regards

[FrancoItaly]

Hello FrancoItaly and all

There is one optimal frequency 115.674 MHz and two variants of HC-49U quartz crystals.
1st. 115.5278 MHz main freq.
2nd. Overtone quartz 10.695 MHz or 10.700 MHz both are near geometric mean of main LC resonant tanl circuit.
L1 3 turns, wire diameter 1mm, 1.09mm enamelled, at 10 mm coil form, 10.5 mm lenght of coil with 3mm winding pitch.
Primary inductance 0.086 uH or 86 nH
Series resistance - 2.304 mOhm
Parallel resistance - 38.14 KOhm
Parallel capacitance Cs - 0.338 pico
Self resonant freq Fsr is very high 1.0895 GHz, wit Q-factor 619 and ESR 0.1 Ohm at 115.674 MHz
Together wit C10 ~ 22 pico, -3dB(Δf) bandwidth of parallel tank-circuit L1C10 is 302.5 KHz, Z= 63 Ohm and eq.resistance is Req = 21.93 KOhm.
Very probably LRL range is somewhere plus or minus 5Mhz from main oscillating LC tank-circuit freq. It should be from 110.5Mhz - 120.5 MHz. Phenomenon is very complex and no one living could explain it. It's all matter of experiments.

Regards

Thanks for all these calculations, the 20 Mhz version operates by tuning L1/C10 on a higher harmonic of 20Mhz, thus increasing the efficiency of the mixer and therefore with a greater sensitivity of the sensor stage. The main problem is to avoid self oscillation.

[FrancoItaly]

My youtube channel

https://www.youtube.com/watch?v=BQ3aaN044MA

https://www.youtube.com/watch?v=wtgtj7G6L6U

https://www.youtube.com/watch?v=Sl4VtAmxCm0

https://www.youtube.com/watch?v=yR3tzT2Jd-g

[omar]

Hi Franco, why didn't you use a germanium diode? It has a wide range and ten times more sensitivity than a silicon diode 4148.

[FrancoItaly]

Hi Franco, why didn't you use a germanium diode? It has a wide range and ten times more sensitivity than a silicon diode 4148.

Germanium diodes are clearly inferior to silicon ones, the only advantage is to use them where a lower voltage drop is required. I don't understand what you mean by higher sensitivity, diodes don't amplify.

[Inna]

Low battery...

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.

[Pahom]

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]

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]

P2 potentiometer

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]

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]

Potentiometer or trimmer?

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.