Andy Flind MFD.

[Geo]

Originally Posted by abdou2014

Is the preamp necessary ?

I believe yes.
Esteban was telling that one friend of him found a big silver "treasure" without the use of preamplifier. The commercial lrl use preamp

[Geo]

Originally Posted by brs

Hi Geo
has certainly worked on this machine and its results are satisfactory

Hi.
i constructed it long many years ago (maybe 10+) with all mods and adds.
Results at my area was not good. It located only some small objects from short distance.
I keep it yet
It is a good way for someone to construct a lrl and play with it with little money, compared with the money that has the commercial

[abdou2014]

Thank you Mr Geo :

I want to put only one JFET, is it better ?

what is your advice (BF 245 OR 2N3819) ?

I know you do not like working with 59 Khz, what do you recommend me ( 80Khz or 85Khz ) ?

[Geo]

The basic is to put the preampl inside the coil. Also a potentiometer to control the gain of preamp is neccessary. I don't know who freq is the best for your area. Play with all by changing the tuning capacitor. I prefer 80 ... 100Khz.
I attach a photo from the head of my lrl...

[abdou2014]

Thank you !

[abdou2014]

Between the preamp and The Amplifier IC1, what are the changes for (C1 - R3) ?

[Geo]

Originally Posted by abdou2014

Between the preamp and The Amplifier IC1, what are the changes for (C1 - R3) ?

Make C1= 47n and connect a resistor 1M between pin2 and ground (IC1a)

[abdou2014]

I'm designing the circuit board . Thanks for your help

[abdou2014]

For the coil I think a big inductor is more sensitive except that it may react to interferences,

what is the best Coil for this device ?

[Mike(Mont)]

Happy Birthday Geo!

Looks interesting enough to experiment with.

[GOLDEN LILLY]

Hi folks, I build an lrl based on the original schematic of Andy with some modification that is more sensitive and directional. Pre-amp is still used, values of the components like capacitors and resistors are changed, audio stage are also changed, Ic's are also changed which make this lrl very reliable to use.

[abdou2014]

That's what I'm doing, you want to help or scare ???

[Geo]

In place of speaker you can use a beep generator.

[abdou2014]

we connect the audio output directly in the 555, or we add 100nF + transistor between two

resistor 680K ?

[Geo]

Do you have the schematic of Alonso's PD???

[Geo]

Originally Posted by Mike(Mont)

Happy Birthday Geo!

Thanks Mike and Sneshko

[abdou2014]

We have to change nothing in the original diagram except C1 - R3, you confirmed ?

[abdou2014]

I think (mineoro special series 2000 and Iconos md) are prototipe Andy flind modified ?

[Geo]

Originally Posted by abdou2014

I think (mineoro special series 2000 and Iconos md) are prototipe Andy flind modified ?

No....
I asked you if you have shematic of PD????

[Geo]

Originally Posted by abdou2014

We have to change nothing in the original diagram except C1 - R3, you confirmed ?

you will see on the way...
It is better to make a pcb only for beep generator and another one for coil preampl.
Also it is better to use different power supply for beep generator and for preampl.
Only you will see the problems and what mods to make...

[abdou2014]

I'm sorry, I have clone Alonso-PD schematic ,

[indiana jones]

Originally Posted by Geo

Hi.
All these years i received so many mails to post the schematic of Andy Flind.
Today i decided to post it here.
Article is in PDF format and it is from EPE magazine.
I would like Admin to tell me if i can do it or No. Article is from year 1995.

Regards

Thanks Geo

for me, one of the best lrl

[Geo]

Hi Chris, how are you.
Try this project, maybe to have good results at your are.

[Geo]

Originally Posted by abdou2014

I'm sorry, I have clone Alonso-PD schematic ,

So you can use the beep generator from PD. A 100nf at input is ok.
Try to connect it to output of IC4.
IC5 is a tone generator, we don't need it because beep generator uses beeper with internal oscillator.

[abdou2014]

Thank you Geo !

Beep generator from PD !