FM Ratio Detector is not working

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The FM ratio detector circuit was initially not producing an audio signal due to a lack of connection between the AUDIO OUT line and the audio side of the detector. Troubleshooting revealed that the transformer values were incorrect, and adjustments were made to ensure both the primary and secondary resonant circuits were tuned to the same frequency. After changing the value of the IF transformer as suggested, the circuit began to work properly. A user also inquired about proper capacitor connections for their own circuit issue. The discussion emphasized the importance of correct component values and connections for successful circuit operation.
michael1978
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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
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michael1978 said:
this circuit, is not working i don't get audio signal
Comparing your ratio detector circuit with the standard design, reveals the problem.

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NascentOxygen said:
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?
 
michael1978 said:
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.
 
NascentOxygen said:
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...
 
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NascentOxygen said:
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
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this is similiar
 

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sorry the voltage of SFFM must be 1V
 
  • #10
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
 
  • #11
Tom.G said:
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….
 
  • #12
Tom.G said:
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.
 
  • #13
michael1978 said:
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?
 
  • #14
Thanks everyone i fixed……...:wink:
 
  • #15
michael1978 said:
Thanks everyone i fixed……...:wink:
How? What did you change to make it work?
 
  • #16
Tom.G said:
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
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  • #17
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 !
 
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