FM Ratio Detector is not working

[michael1978]

hi ,
please
can somebody help me about this circuit, is not working i don't get audio signal
here is my circuit rename in asc frm txt
thanks

 

[Svein]

An FM detector is a complicated thing. I would use a dedicated IC - for example http://www.onsemi.com/pub/Collateral/ENA2052-D.PDF. You can also get the complete receiver in an IC: http://www.onsemi.com/pub/Collateral/EN8271-D.PDF.

 

[NascentOxygen]

this circuit, is not working i don't get audio signal

Comparing your ratio detector circuit with the standard design, reveals the problem.

 

[michael1978]

An FM detector is a complicated thing. I would use a dedicated IC - for example http://www.onsemi.com/pub/Collateral/ENA2052-D.PDF. You can also get the complete receiver in an IC: http://www.onsemi.com/pub/Collateral/EN8271-D.PDF.

Hi, Svein, thank you i know, but i wil like this one to make it work,

 

[michael1978]

Comparing your ratio detector circuit with the standard design, reveals the problem.

View attachment 233930

hello NascenOxygen, in my book it looks like this, so what do you think where is the problem?

 

[NascentOxygen]

hello NascenOxygen, in my book it looks like this, so what do you think where is the problem?

There is no path linking your AUDIO OUT line to the audio side of the detector.

 

[michael1978]

There is no path linking your AUDIO OUT line to the audio side of the detector.

from this circuit i did it in ltspice i thought he going to work but not

is not audioouput the output from detector? of where is? in my book the output is taken from the audiooutput, after send to ic lm386 TO MAKE IT STRONGER THE audio signal...

 

[michael1978]

There is no path linking your AUDIO OUT line to the audio side of the detector.

look this circuits from book, what do you think what for mistake i make

this is similar

 

[michael1978]

sorry the voltage of SFFM must be 1V

 

[Tom.G]

Your circuit looks good to me.
Is it the simulation that does not work or the circuit that you built?
The simulation you posted is a Transient analysis. But you need an AC analysis to get audio output.
If the circuit you built is not working, do the usual troubleshooting. Check all wiring and make sure the parts are the right values.

Cheers,
Tom

 

[michael1978]

Your circuit looks good to me.
Is it the simulation that does not work or the circuit that you built?
The simulation you posted is a Transient analysis. But you need an AC analysis to get audio output.
If the circuit you built is not working, do the usual troubleshooting. Check all wiring and make sure the parts are the right values.

Cheers,
Tom

Hello Tom, i think that, the value of L2 L3 are not correct, but i going to try to looks everything is ok wiring
Have a nice day….

 

[michael1978]

Your circuit looks good to me.
Is it the simulation that does not work or the circuit that you built?
The simulation you posted is a Transient analysis. But you need an AC analysis to get audio output.
If the circuit you built is not working, do the usual troubleshooting. Check all wiring and make sure the parts are the right values.

Cheers,
Tom

Hi Tom, i check all wiring, eveything is okey, i change the values of transformer, they change, but is not working.

 

[NascentOxygen]

Hi Tom, i check all wiring, eveything is okey, i change the values of transformer, they change, but is not working.

The transformer primary and secondary are resonant circuits, and I think they are supposed to both be tuned to resonate at the same frequency. So as you sweep the input frequency, monitor the transformer primary and secondary signals and make sure their signal peaks do co-incide. Trim the capacitances until the peaks do coincide, and at the design frequency.

Are you saying the simulation works okay, but your wired circuit does not? Or does neither work as expected?

 

[michael1978]

Thanks everyone i fixed……...

 

[Tom.G]

Thanks everyone i fixed……...

How? What did you change to make it work?

 

[michael1978]

How? What did you change to make it work?

HI, somebody told me, to change the value of IF transformer he show me the value… now is working
here

 

[Zlatko1969]

Hello
I have similar problem but with circuit I build not with simulation
which by the way show nothing,
I use BLUE i.f. transformer which should be FM detector and now from the answers above
which solution is proper.

1.This one where two 1nF caps connection goes to audio output before 7.5k resistor
2.This one where two 1nF caps connection goes to GND
thanks !