On Fri, 21 Apr 2006 21:54:39 GMT, Telamon
wrote:

In article ng22g.739$5z3.735@trndny01, HFguy
wrote:

Are you sure about the patent cost? I thought sync detection was mostly
implemented through a PLL type circuit. You can buy this circuit on a
chip with a handful of support components for it to function. Maybe you
have to add a reference oscillator to the circuit with the other support
components. Anyone should be able to buy and use these designs.

A PLL and a Product Detector

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

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?

"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

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

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.

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.