AM Demodulator: SSB -> AM; Op Amp?

[Voltux]

Greetings Physics Forums,

I'm reading up on Radio Circuits and studying for my General's Amateur Radio License and was learning about AM Demodulators.

I understand that in AM you can use a peak detector to get the modulated audio out however in SSB radio don't you have to double the signal so as to invert it to produce the AM and then demodulate it?

So seeing if the above is correct would it be possible to just input the SSB Signal into an Op-Amp in both the inverting and non-inverting inputs to end up with the AM signal?

Thanks for everyone's time, I appreciate it! :)

Respectfully,
Voltux

 

[Averagesupernova]

No. You cannot do that. You need the original carrier back to get the audio out of a SSB signal. In receivers this is called the BFO, or beat frequency oscillator.

 

[vk6kro]

The usual method of recovering SSB is to convert it to an intermediate frequency (say 14 MHz to 455 KHz) then pass it through a crystal filter at 455 KHz, then amplify it and then inject a 455 KHz local oscillator signal at a frequency corresponding to where the carrier would have been if this was an AM signal.

This is done with a product detector, which is a type of mixer. The oscillator used like this is a BFO. Beat Frequency Oscillator.

The output of this is audio which you then amplify and send to a speaker.

You may be able to use an opamp for some of this, but there are specialized chips like the NE602 and SA612 which work very well as product detectors and mixers.

 

[Voltux]

The usual method of recovering SSB is to convert it to an intermediate frequency (say 14 MHz to 455 KHz) then pass it through a crystal filter at 455 KHz, then amplify it and then inject a 455 KHz local oscillator signal at a frequency corresponding to where the carrier would have been if this was an AM signal.

This is done with a product detector, which is a type of mixer. The oscillator used like this is a BFO. Beat Frequency Oscillator.

The output of this is audio which you then amplify and send to a speaker.

You may be able to use an opamp for some of this, but there are specialized chips like the NE602 and SA612 which work very well as product detectors and mixers.

Thanks! Consider my question solved. I'm following Scott Harden's plans for the SA612 and reading through the 2011 ARRL Handbook for Radio Communications as well. Just trying to get a block view I suppose of how a SSB Receiver would work as opposed to an AM.

http://www.swharden.com/blog/ - For those interested.