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David wrote:
wrote: Are you sure about the patent cost? I thought sync detection was mostly implemented through a PLL type circuit. A PLL and a Product Detector You can do without the PLL, too. You just create the signal with a separate stage that overamplifies the signal into clipping, then you have basically a sorta-square wave to feed into the product detector. -- All relevant people are pertinent. All rude people are impertinent. Therefore, no rude people are relevant. -- Solomon W. Golomb |
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On Fri, 21 Apr 2006 17:46:36 -0500, clifto wrote:
David wrote: wrote: Are you sure about the patent cost? I thought sync detection was mostly implemented through a PLL type circuit. A PLL and a Product Detector You can do without the PLL, too. You just create the signal with a separate stage that overamplifies the signal into clipping, then you have basically a sorta-square wave to feed into the product detector. Does that work when the station carrier fades? |
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"David" wrote in message ... On Fri, 21 Apr 2006 17:46:36 -0500, clifto wrote: David wrote: wrote: Are you sure about the patent cost? I thought sync detection was mostly implemented through a PLL type circuit. A PLL and a Product Detector You can do without the PLL, too. You just create the signal with a separate stage that overamplifies the signal into clipping, then you have basically a sorta-square wave to feed into the product detector. Does that work when the station carrier fades? Not as well in deep fades as a 'truly' synchronous detector. That's often called a 'quasi-synchronous' detector since there is not a synchronised oscillator, just the amplified carrier, mixed with the signal in the product detector. Tom |
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David wrote:
On Fri, 21 Apr 2006 17:46:36 -0500, clifto wrote: David wrote: wrote: Are you sure about the patent cost? I thought sync detection was mostly implemented through a PLL type circuit. A PLL and a Product Detector You can do without the PLL, too. You just create the signal with a separate stage that overamplifies the signal into clipping, then you have basically a sorta-square wave to feed into the product detector. Does that work when the station carrier fades? I've wondered the same thing. But there apparently are receivers using that technique. http://www.radio-electronics.com/info/receivers/synchdet/sync_det.php describes the principle; see especially the diagram captioned "A synchronous detector using a high gain-limiting amplifier to extract the carrier". -- All relevant people are pertinent. All rude people are impertinent. Therefore, no rude people are relevant. -- Solomon W. Golomb |
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On Sat, 22 Apr 2006 01:44:27 -0500, clifto wrote:
David wrote: On Fri, 21 Apr 2006 17:46:36 -0500, clifto wrote: David wrote: wrote: Are you sure about the patent cost? I thought sync detection was mostly implemented through a PLL type circuit. A PLL and a Product Detector You can do without the PLL, too. You just create the signal with a separate stage that overamplifies the signal into clipping, then you have basically a sorta-square wave to feed into the product detector. Does that work when the station carrier fades? I've wondered the same thing. But there apparently are receivers using that technique. http://www.radio-electronics.com/info/receivers/synchdet/sync_det.php describes the principle; see especially the diagram captioned "A synchronous detector using a high gain-limiting amplifier to extract the carrier". The extracted carrier should be used to lock a locally generated carrier, with sufficient hysteresis to free run accurately during selective fades. |
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clifto wrote:
David wrote: wrote: Are you sure about the patent cost? I thought sync detection was mostly implemented through a PLL type circuit. A PLL and a Product Detector You can do without the PLL, too. You just create the signal with a separate stage that overamplifies the signal into clipping, then you have basically a sorta-square wave to feed into the product detector. That's the poor man's sync' detector. It works but it's no match for using a PLL with sideband phase cancellation. That's what made the Drake system so good. |
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