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Most AM receivers use Envelope detection. Historically this was simple. PLL-based systems are slightly better at low carrier-to-noise levels. Would there be any SNR advantage if each sideband was detected separately? Would the correlation of the LSB and the USB be useful because the noise in general is not correlated? Could this be better than a PLL at higher carrier-to-noise ratios? Would putting each detected sideband into say each ear of some headphones or Left and right stereo channels give good results by allowing the ear to do some processing?

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That's a lot of questions!

Would there be any SNR advantage if each sideband was detected seperately?

Would the correlation of the LSB and the USB be usefull because the noise in general is not correlated?

Well, that's exactly what envelope detection does: It takes advantage of the fact that the correlated signal energy in the two sidebands doubles the detector output, while the uncorrelated noise energy only contributes 1.4×.

Could this be better than a PLL at higher carrier to noise ratios?

No. Whether or not you use a PLL for synchronous detection is orthogonal to this issue. In general, the overall advantages of using synchronous detection would be far greater than what you're proposing. Besides, how would you "detect the sidebands separately" without using synchronous detection, or something functionally equivalent to it?

Would putting each detected sideband into say each ear of some headphones or Left and right stereo channels give good results by allowing the ear to do some processing?

That is in fact how one AM stereo system works. The effect on a mono signal is that you perceive the signal to be "in the middle of your head", while the noise is spread out from ear to ear.

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  • $\begingroup$ @ Dave Tweed good to see an answer ,I was thinking that each sideband would be seperately detected by say a USB filter and a LSB filter at the common IF of 455 KHz .This would mean that a add on circuit could be constructed to show a IN Vs OUT comparison to see if there is any improvement.If there was then these days people may prefer to use a DSP .These days signal processing is cheap so stuff that was not worth it when AM was invented might be useful now. $\endgroup$ – Autistic Oct 1 '16 at 20:32

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