Hi guys!

I saw this term mentioned in the specs of a radio. What does it mean
exactly? That if you hope and listen long enough you can convince yourself
it's synchronous?

Lucky

Lucky wrote:

Hi guys!

I saw this term mentioned in the specs of a radio. What does it mean
exactly? That if you hope and listen long enough you can convince yourself
it's synchronous?

Which radio?

dxAce
Michigan
USA

Lucky wrote:
Hi guys!

I saw this term mentioned in the specs of a radio. What does it mean
exactly? That if you hope and listen long enough you can convince yourself
it's synchronous?

Lucky




Which radio. The term could mean a variety of things, but if you want a
specific answer, please indicate which radio and provide a link to the
use of the ter,.

Then, somone may be able to provide the correct (exact) answer.

craigm

Which radio...haven't heard that term.

Quasi synchronous detection is a non-PLL type of sync detection.......like
the type that was used in the Drake R7 receiver. Basically, it consists of
using a mixer to demodulate the AM signal in this way: the I.F. signal is
split into two paths.
The unprocessed I.F. signal (one of the paths) is applied to the RF port of
a mixer, while the other path is squared up through a limiting amplifier and
applied to the LO port of this same mixer.
The demodulated audio is taken from the I.F. port (output port in this case)
of the mixer.
I did a similar design a couple of years ago, using a Philips SA637 Digital
FM Receiver chip. Philips discontinued that device so I went with the AD607
for my subsequent design.
I hope this helps.

Pete

"John S." wrote in message
ups.com...
Which radio...haven't heard that term.

Pete KE9OA wrote:

Quasi synchronous detection is a non-PLL type of sync detection.......like
the type that was used in the Drake R7 receiver. Basically, it consists of
using a mixer to demodulate the AM signal in this way: the I.F. signal is
split into two paths.
The unprocessed I.F. signal (one of the paths) is applied to the RF port of
a mixer, while the other path is squared up through a limiting amplifier and
applied to the LO port of this same mixer.
The demodulated audio is taken from the I.F. port (output port in this case)
of the mixer.
I did a similar design a couple of years ago, using a Philips SA637 Digital
FM Receiver chip. Philips discontinued that device so I went with the AD607
for my subsequent design.
I hope this helps.

Ahhhhh yes, in the Drake R7 it's known as "synchro-phase" detection.

dxAce
Michigan
USA

I believe that Kiwa detector that went on eBay recently was of this design.

"John S." wrote in message
ups.com...
Which radio...haven't heard that term.

In article ,
Pete KE9OA wrote:

"John S." wrote in message
oups.com...

Which radio...haven't heard that term.

I believe that Kiwa detector that went on eBay recently was of this design.

A guy I know who knows Craig a lot better than I do said that it used some
chip designed for VCRs. (My wild ass guess would be a Philips video IF
and detector chip with the synchro-phase circuit in it. TDA2540, TDA2541).

Mark Zenier Washington State resident

Mark Zenier ) writes:
In article ,
Pete KE9OA wrote:

"John S." wrote in message
roups.com...

Which radio...haven't heard that term.

I believe that Kiwa detector that went on eBay recently was of this design.

A guy I know who knows Craig a lot better than I do said that it used some
chip designed for VCRs. (My wild ass guess would be a Philips video IF
and detector chip with the synchro-phase circuit in it. TDA2540, TDA2541).

Mark Zenier Washington State resident


Are we talking what's no called "quasi-synchronous"?

Decades ago, Motorola had the MC1330 which was a mixer and a limiter
in one package, and intended as a quasi-synchronous detector in tv
sets.

I suspect if driven properly, the MC1350 IF amplifier would do it, since
the stage that is voltage controlled is just a "Gilbert Cell Mixer".

When the MC1496 Mixer (a "Gilbert Cell" long before the term was applied)
came out in the early seventies, there was an article in Ham Radio magazine
about it, I think by Roy Hejhall, and one of the examples was as a
"quasi-synchronous" detector, though I'm not sure if it explained it
as such or just as a fancy AM detector. Didn't even need a limiter, if
you fed a strong enough signal into it. The datasheet or application note
for the MC1496 includes the circuit.

Of course, there have also been examples of them based on FM detectors.
Many of those in ICs used a scheme that included a balanced mixer, and
of course it had the limiter, so all you had to do was hook it up.

Michael

jimg wrote:
in basic comm text books this is called is called 'coherent'
detection. under certain conditions it can be demonstrated that the
coherent demodulated snr is a 3-4 dB better than the "diode"
(non-linear self-mixing) demod and a 3-5 dB worse than synchronous
demodulation. under severe fading the coherent demod can actually
underperform the diode demod depending upon the mixer/post-filter/etc.
whereas the synchronous pll output can maintain the mixer input even
if the signal disappears briefly (wrt the loop time constant and phase
detector type)

because of the fading performance, the ease creating high quality
quadrature pll outputs, and the inherent input phase noise attenuation
in the pll, it's (coherent demodulation) almost never used anymore in
mixed signal designs...

Hi guys!

I saw this term mentioned in the specs of a radio. What does it mean
exactly? That if you hope and listen long enough you can convince yourself
it's synchronous?

Lucky


jimg
Oregon
USA