Lrl from Italy

[Napsterce]

Hello Franco, this is my pcb layout by your pcb hand drawing, it's not double sided, how should i shield it? The small pcb is display stage, will it make some problems to be like this or should i remove it from there? If you notice some irregularities please tell me. I am using 12v battery but it is not regulated and the voltage is 12.47 and keeps going down as i use the lrl (i don't use it more than 12v), should i put a regulator or is it ok like this? Thank you.

[FrancoItaly]

Hi Napsterce,

the shield is not strictly necessary, but you can use a foil of aluminum glued on the lower part of PCB or another PCB. I advise against the use of a 12V battery which feeds directly the sensor stage and the other circuits, You have to use 2 X 9V batteries (then 18V in total) and a 7812 (IC stabilizer), I repost here the schematic. The display stage close to sensor stage do not create problems, but for me it's important hold your hand quite far from sensor stage then I recommend using a long enough handle (25-30 cm).

Best Regards

[Napsterce]

Hi Franco, i have aluminium foil which is with glue (it's like duct tape but it is made from aluminium), i will glue it to the bottom side of the pcb and i will connect it to ground (battery negative). Also i am in process of building the second lrl and in the second one i will made the 2x9v battery power supply with 7812 IC and i will make a comparation which one is better. I'm giving the lrl's names N°1 and N°2. N°1 will be with 2x9v power supply, L1 = 3 turns and C10 = 22pF. N°2 will be with 12v battery, L1 = 2-4 turns and C10 = 22pF + 22pF variable capacitor. Why you advise against using 12v battery? The voltage is stable, it needs at least 1 hour using to reduce the voltage from 12.47v to 12.20v. Also on N°1 u use stylus antenna 60cm and plastic handle 20cm long. N°2 is in process of building but the handle will be also 20-25cm long and a stylus antenna (still searching for it). Also wanted to ask you, how about connecting 60cm antenna on C9-C10-L1 (your antenna connector) and 3 smaller antennas (10-15cm) to TR2? Or to connect them together with the big antenna? Best regards.

[FrancoItaly]

If the battery voltage is stable use it as well, but I prefer the stabilization. Regarding the antennas I would try the one at a time.

Best Regards

[afshin]

As several new members of this forum have asked me privately tips for building my LRL, want to do a little summary about its construction and calibration.
The quartz and TR1 constitute the internal oscillator, TR2 is the mixer to which the 8Mhz signal arrives along with the "phenomenon" picked up by the antenna. TR2, TR3 and TR4 are the high gain amplifier, TR5 takes the signal (rectified by diodes) with high impedance and on the emitter there is the signal with low impedance. R15, R16, C17 and C18 are a low pass filter that cancels signal residues at 8 Mhz. I repost schematic and PCB. It's better to use a double face PCB, on one side we sold the components and the other side there is the shield
connected to ground, to avoid self oscillations. It's preferable to use transistors type BC...C because the high beta (gain), I use BC183C because I have a lot but work well also BC549C, BC109C, BC239C and others. All sensor stage is powered by 12V stabilized. For the first test do not connect quartz then look at out point, the DC voltage must be 0V. If not the stage is self oscillating then you must decrease the gain by changing C13 and C14 (from 560pF to 470pF or less) until there are no more oscillations.
Now connect quartz and measure out voltage, if the voltage is yet 0 you have to control the emitter of TR1, if the oscillator is ok it must be a 8Mhz signal of few volts peak to peak, otherwise change C1, for example from 330pf to 470pF or more. Signal out is better in the range 5-6V, if it is more then 6V you have to decrease C2,C3 and C4, sometimes it's sufficient the parasitic capacitance of PCB (removing C2, C3 and C4) or you can use instead of C2-C3-C4 two wires of about 6 cm twisted between them. If signal out is less than 5V you have to increase c2-C3-C4, for example if you use only C2 you have 1pF, if you use only c3-C4 connected in series you have 0.5 pF and so. To test if everything is ok touch the antenna and the out must decrease (100 - 200 mV or more). The target is signaled by an increase of the output voltage.

Hi Dear Franco
thank you for guidance members, you described your lrl parts how do work except one,and that is L1,C10 filter role.If this lrl works in 8 Mhz but this LC frequency is high about 100Mhz,is it low pass filter or high pass or band pass or band stop filter? What is it role? And if we eliminate it what will happen?
Thank you

[Napsterce]

Dear Franco, can i use wooden box made from thick (3mm) wood or it is better to be in plastic box?

[FrancoItaly]

L1/C10 is pass band filter, if you remove L1/C10 or change values (more than 3 turns or less than 2 turns) the lrl don't work. The 8Mhz signal is somehow modulated by the "phenomenon" and this may vary from 3 to 10 Mhz. I can even add that frequencies of about 60 kHz do not work.
Much as regards the box, I always use plastic (easier for me to work) but I would think the wood is suitable, since there is not involved static electricity.

Best Regards

[brs]

dear franco
If we put instead of 8 mhz 9 or 10 mhz Are performance differs

[afshin]

L1/C10 is pass band filter, if you remove L1/C10 or change values (more than 3 turns or less than 2 turns) the lrl don't work. The 8Mhz signal is somehow modulated by the "phenomenon" and this may vary from 3 to 10 Mhz. I can even add that frequencies of about 60 kHz do not work.
Much as regards the box, I always use plastic (easier for me to work) but I would think the wood is suitable, since there is not involved static electricity.

Best Regards

Hi dear Franco,Thank you,
But It seems to be a band stop filter,Because the LC resonance waves received by the antenna go to the circuit ground with a minimum Impedance by LC, instead of
go to the base of Tr2 for mixing
and modulation with the 8 Mhz
,and it is strange. actually All frequencies pass and go to mixing and modulation except the LC frequency!!
while it should be inverse.
actually if this is a pass band filter has to be this form,I drew
What is your opinion dear franco?
Best regards

[mustefa ubram]

Hi dear Franco,Thank you,
But It seems to be a band stop filter,Because the LC resonance waves received by the antenna go to the circuit ground with a minimum Impedance by LC, instead of
go to the base of Tr2 for mixing
and modulation with the 8 Mhz
,and it is strange. actually All frequencies pass and go to mixing and modulation except the LC frequency!!
while it should be inverse.
actually if this is a pass band filter has to be this form,I drew
What is your opinion dear franco?
Best regards

hi freind
You are misunderstanding the concept of filter.When used electronics components that are full use.You painted the wrong input and output filter.In the picture You drew of capacitance and inductance are virtually out of the circuit Only have a connected base with circuit Not applicable in the circuit.

https://en.wikipedia.org/wiki/Low-pass_filter

[mustefa ubram]

hi franco
I have about 2.5 volts in standby mode the sensor output.And about 6 volts when the full reaction.
Is the low 2.5 volts?
In this case a very high sensitivity to the waves

[FrancoItaly]

Hi afshin,

L/C pass band filter at the resonance frequency it has a very high impedance and being placed between the antenna and ground leaves pass without attenuation only the resonant frequency signals, while it is almost a short circuit for the other frequencies.

Best Regards

[FrancoItaly]

Hi mustefa,

the output voltage is ok in 1-6V range, but I recommend about 5V because this way ensures that the sensor stage has the maximum gain possible without distortion, however also 1V can be compensated with a higher amplification in the display stage. The output voltage depends on two factors, one it's the sensor stage gain and the other is the amount of 8Mhz signal that goes to base of TR2. This is why I recommend to remove (or rather not sold immediately) quartz and find the right values for maximum gain without self-oscillation. Only after we can determine the values for C2 / C3 / C4.

Best Regards

[abdou2014]

Mr Franco you say that 3 turns running well in your region italy and switzerland ,What you recommended for the southern countries , to add a turn or remove a turn ? Thank you !

[FrancoItaly]

For my experience 2 or 3 turns work well, 1 or 4 turns do not work. For other country I don't know, but I think it's the same thing, you just have to try.