I need help with building audio decoder

[Marmelado]

decoder sca fm

Hi!

I want to build an audio decoder but i dont know what to use, i know that the input frequency is 15632hz, and i think i have to use a pll and a demodulator, are there any schematics that can help me?

Thanks!

Marmes

 

[flatulent]

inverted audio decoder

You need to describe more about your application. If you want a SCA subcarrier decoder for FM broadcast stations, there are many kits available for around $15. If you want to make your own, exar has a good pll whose data sheet can be found at **broken link removed**

If you are trying to decode other methods, some use inverted audio and you lock the PLL onto the tone that you suggest and then mix (multiply) the tone with the encoded/inverted audio. You can use a four quadrant multiplier IC.

 

[Marmelado]

audio spectrum analyzer

Hi!
Thanks for you answer!
All i want is this, i have an encoded sound, i know it's in a 15.632khz, and all i want is to decode it, but i am still learning electronics, so if any one of you can help me, that would be awesome!

Thanks!!

Marmelado

 

[flatulent]

here is the answer

I downloaded your file and examined it on a software spectrum analyzer. They have modulated the audio onto a 15.632khz carrier in a double side band suppressed carrier fashon. To decode it you have to multiply the received signal by the frequency you stated. You can use an analog multiplier IC. The downoladed file appeared to be voice. If this is true you do not need extreme fidelity and you can use a local audio signal generator. For a first try, you can use any nonlinear device for the multiplier, such as a voltage divider with a series resitor to the output sourced by the signal and a shunt transistor across the output with the base driven by the audio signal generator set to 15.632khz. You can fine tune the audio generator for the best quality of the decoded output.

Perhaps now that I have identified the signal type, some other person will remember some source for a decoder circuit that is drawn out and tell you about it.

 

[Marmelado]

what software spctrum analizer did you use?

Thanks!

Marmelado

 

[flatulent]

cd spectrum pro

I got CD/spectrum pro from download.com by putting audio analyzer into the search field. This has a crude bar graph. Some of the other selections of programs might do better.