Lrl from Italy

[FrancoItaly]

the 12v power supply is stable, test with voltmétre, but the led goes Off alone after each setting ???

If the sensor stage output is steady as 12V supply the only explanation may be that the body affects the regulation, try to adjust the threshold to a higher level so as to be the first led on and find the point where moving the hand off the led turns off.

[abdou2014]

I use the display 1 led, and when I approach my hand from the antenna the led lights, I think it's the opposite.

[FrancoItaly]

I use the display 1 led, and when I approach my hand from the antenna the led lights, I think it's the opposite.

I mean that by moving your hand away from the control of the threshold the LED turns off, so you have to adjust the threshold so as to have the LED on and find the right position with which the LED turns off moving away.

[abdou2014]

the pot threshold does not react to my hand, my hand near or far is the same thing for the LED,
the LED light only when my hand is near to the telescopic antenna , how inverted and make the led turn off instead of it turns on near the antenna ???

[abdou2014]

I'm going to change the pcb, the old one was perfect, I found a misterious method to suppress the sky effect

[FrancoItaly]

the pot threshold does not react to my hand, my hand near or far is the same thing for the LED,
the LED light only when my hand is near to the telescopic antenna , how inverted and make the led turn off instead of it turns on near the antenna ???

As I said before, touching the antenna is a way to empirically establish if the sensor stage is properly tuned. Normally the signal decreases but it may happen that instead the signal increases, so it is not a malfunction of the lrl.

[FrancoItaly]

I'm going to change the pcb, the old one was perfect, I found a misterious method to suppress the sky effect

I'm curious to know how your system works. It may be possible to increase sensitivity and perhaps even have some discrimination.

[Dubulumach]

Hello FrancoItaly

Your LRLs work but suffer from so called "Albedo problem". What is it ?
When you enter in range of Halo-effect field with telesopic antenna you have already disturbed the field. Your antenna need extreme loosy coupling with ambient, to be at maximum sensitivityy not disturbing the field. Use capacitive coupling between two very small capacitors or two very small inductors at the end of your antenna. Also good high impendance RC filter is needed to reject iron targets or selective LC filters, each tuned for specific color metal.

Best Regards
Dubulumach.

[FrancoItaly]

Hello FrancoItaly

Your LRLs work but suffer from so called "Albedo problem". What is it ?
When you enter in range of Halo-effect field with telesopic antenna you have already disturbed the field. Your antenna need extreme loosy coupling with ambient, to be at maximum sensitivityy not disturbing the field. Use capacitive coupling between two very small capacitors or two very small inductors at the end of your antenna. Also good high impendance RC filter is needed to reject iron targets or selective LC filters, each tuned for specific color metal.

Best Regards
Dubulumach.

Hi Dubulumach,
I have experience only on land in Italy and Switzerland (near Italy), also a member of the forum that lives in central america confirms the same thing, that is my lrl (but I think all the others) are insensitive to iron, I believe that iron does not emit the phenomenon. Certainly if the gain is too high the compass effect appears and also many other disturbances of which I do not know the origin. I can think of small metal fragments (non-ferrous) or radio transmitters whose fundamental frequency or harmonic (lower or upper) falls within the range of L1 / C10.
As a general rule if the disturbance remains constant while walking it is the compass effect or some electromagnetic disturbance, while if it disappears after a few meters it is almost certainly a small piece of metal that maybe the MD can not reveal:

Best Regards

[Dubulumach]

Hy FrancoItaly

Why don't you try frontend preamplifier for example from Mineoro DC210 which Geo has discloded.? Or use RF sniffer from DCH85 with TDA7000 tunnd at 110-120Mhz ?

Any horizont effect (sky/ground) make lrl prospecting impossible, right ?

Best Regards
Dubulumach

[abdou2014]

I made this modification franco lrl with tda7000, it did not work, I found two ways to eliminate the effect of the sky, but I have not yet tried in the test field, but a great sensitivity and discrimination for different fields

[Dubulumach]

I made this modification franco lrl with tda7000, it did not work, I found two ways to eliminate the effect of the sky, but I have not yet tried in the test field, but a great sensitivity and discrimination for different fields

analyse this. you need to inject very weak signal (uV) from Franco's oscillator via 0.33pf or less at base of BF494 transistor.

BFO

[abdou2014]

did you build this modification, make us a schema, for me, I connected the output of the TDA to the TR2 mixer .

[Dubulumach]

did you build this modification, make us a schema, for me, I connected the output of the TDA to the TR2 mixer .

No.
Output of TDA7000 is weak audio signal. in fact noise. tune rf sniffer away from any FM station foe example 118-120Mhz.

[abdou2014]

other picturs noT open ???