Andy Flind MFD.

[abdou2014]

Really i can't understand why many members here show how their detector detects an object from 0.1 ... 1m. This is a job for a normal metal detector not for lrl.

it is not the same Mr Geo, these results are without TX, only a receiver, contrary to the metal detector TX RX

[Geo]

it is not the same Mr Geo, these results are without TX, only a receiver, contrary to the metal detector TX RX

What it means??? you can make a metal detector without emiting very easy but it will not be a lrl.....

Ohhh and something else..... most lrls don't work good over or near to targets.

[abdou2014]

I built two models which can detect metal without an emitter:

1 - work as a magnetometer, detect only ferrous metals

2- work as LRL, detect non-ferous metals, in junction with am

[humhum]

km

km

[abdou2014]

Mr Geo i sent you msg

[Geo]

I am interesting to connect a radio inside the Andy's MFD.
TDA7000 is my selection.
Does anyone made this mod???

[abdou2014]

Yes i made it

[abdou2014]

I made all the combinations, and the only problem is the stability, maybe your design is perfect

[Geo]

Did you use transformer to drive the beep generator or you connected the audio out directly (via a cap) to generator input???
What radio did you use??

[abdou2014]

i use transformer between TDA radio and beep , I also have another trick of coupling between a commercial radio and the beep , but there is a difference between commercial and TDA

[abdou2014]

another sensitive display for TDA

[Geo]

Before years when i constructed my first Andy's MFD i had connected a radio via a driver transformer. Now i plan to work a radio based on TDA7000 - LM386 and i am not sure if the output level is enouth to triger the beep generator.
Anyway... the experiment will shows .

[abdou2014]

direct connection lm386 and beep no, you must modify the beep generator or add a transformer , there is also a trick to know the variation of the input signal of the TDA without using the lm386

[Geo]

I believe that lm386 with gain = 50 is enoutgh. TDA7000 has audio output 75mv.Lets say a normal signal will give output 50mv x 50 gain = 2500mv.
2.5v signal is very very ok to triger the transistor before the 555. Also i can try gain = 200 at LM386.
No reason to connect 8R load to LM386.... a bigger one will be ok.

[abdou2014]

what is the resistance value in series with the capacitor for gain of 50