walkie talkie circuit research project

[daniurtasun]

**broken link removed**
hi i need to know how does this circuit work, it is suposed to be a simple walkie talkie schematic. for example i dont get the way the demodulation is done or the modulation itself an so on please is someone able to understand this circuit could you give me a hand?

 

[Hero999]

Look at the schematic when the 4PDT switch is in the T and R positions.

The audio amplifier should be pretty obvious, but I'll give you a hint: the speaker is used as a mic when in transmitting mode.

The receiver is more subtle, it's a crystal oscillator when in transmit and a regenerative receiver when in receive.

I remember having a set of walkie talkies like this when I was a child except I think they had more transistors but I don't remember that well.

 

[flat5]

Some had only 4 transistors. Sony had a subsidiary (started with s, what was it) that exported them to the USA in the early 1960s.

 

[Hero999]

If I remember rightly they were made in China but that doesn't make sense as it was the late 80s and cheap electronics weren't made there back then. I think they were made in the republic of China (Taiwan) not the People's republic.