Andy Flind MFD.

[abdou2014]

Thank you Geo and Qiaozhi

[abdou2014]

What gives this peculiarity in this magnetic detector ???

[Mike(Mont)]

Thanks for the info.

There is a cell phone app titled "Tesla Meter" the icon is a power pole. It has an AC magnetic field detector as well as DC. Don't expect it to be nearly as sensitive, but it's cheap, like a dollar or two. Or do a search for EMF detector. You can even find reviews or which is best.

[Geo]

Happy birthday Geo

Thank you

[Geo]

What gives this peculiarity in this magnetic detector ???

If you mean the Andy Flind then you must search at forum.
Esteban made some modifications and make it a good lrl (as he was telling).
The good is that you can construct the schematic as is (on original pcb) and later to make the mods and maybe the adds. In place of T1 you can use a tuned coil.
With little mods on it there is a very expensive lrl (don't ask me if it works )

[Geo]

Also, while saving the PDF from Geo, I discovered that I had this article from Andy Flind dated 2001:

George Thank you.
It is an interesting article and i have 2 sensors in lab drawers...

[abdou2014]

Is the preamp necessary ?

[brs]

Just asked

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

[Sneshko]

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

Thank you very much dear Geo & Qiaozhi!
...And, Happy birthday Geo!!!
Regards in Serbia!
Sneshko

[Mike(Mont)]

Thanks for the info.

There is a cell phone app titled "Tesla Meter" the icon is a power pole. It has an AC magnetic field detector as well as DC. Don't expect it to be nearly as sensitive, but it's cheap, like a dollar or two. Or do a search for EMF detector. You can even find reviews or which is best.

The app is called Tesla Field Meter by JMS Solutions. Of course not nearly as sensitive.

[Geo]

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]

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 !