[time-nuts] GPS receivers W/timing outputs greater than 1PPS

[Perry Sandeen]

List,

RDR electronics in Colorado has Motorola M12+ OnCore
GPS Timing Receiver 3V 1pps 100Hz for $20.

They also have other GPS units.  Cheaper than chicoms and guaranteed.  Stock 
varies so check from time to time if you don't see what you need.

I'm a multiple happy camper customer.

Regards,

Perrier
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[time-nuts] 60 KHz receiver number

[Perry Sandeen]

List,

60 KHz SYMTRIK Radio
Time Receiver..Item number: 230991713311

Regards,

Perrier
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Re: [time-nuts] 60 KHz receivers

[paul swed]

went to pv electronics direct. They are reasonably priced. But they don't
give the detail needed. I am pretty sure these are the old cmax or temic
chips. Since I don't have one can't really tell you.
Regards
Paul
WB8TSL


On Tue, Jun 25, 2013 at 10:44 PM, paul swed  wrote:

> I looked and did not see the radio
> As to could it work yes. You might have to invert the data.
> Regards
> Paul
> WB8TSL
>
>
> On Tue, Jun 25, 2013 at 10:35 PM, Perry Sandeen wrote:
>
>>
>>
>>
>>
>> 
>> List,
>>
>> On Ebay I stumbled upon a site called pv. electronics from England
>>
>> The site offers a 60 KHz SYMTRIK Radio Time Receiver
>> Module W/100 MM Antenna for $25 delivered.  I don't know if this will
>> work with Paul Sweed's circuits or not.
>>
>> It looks like the stuff Digi-Key used to carry made by IIRC C-SPAN.
>>
>> One can also get modules for the GB and German time transmissions.
>>
>> HTH someone.
>>
>> Regards,
>>
>> Perrier
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>
>
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Re: [time-nuts] 60 KHz receivers

[paul swed]

I looked and did not see the radio
As to could it work yes. You might have to invert the data.
Regards
Paul
WB8TSL


On Tue, Jun 25, 2013 at 10:35 PM, Perry Sandeen  wrote:

>
>
>
>
> 
> List,
>
> On Ebay I stumbled upon a site called pv. electronics from England
>
> The site offers a 60 KHz SYMTRIK Radio Time Receiver
> Module W/100 MM Antenna for $25 delivered.  I don't know if this will work
> with Paul Sweed's circuits or not.
>
> It looks like the stuff Digi-Key used to carry made by IIRC C-SPAN.
>
> One can also get modules for the GB and German time transmissions.
>
> HTH someone.
>
> Regards,
>
> Perrier
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Re: [time-nuts] Spectracom 8164 Hack?

[paul swed]

Reasonable opens all kinds of doors.
The recvr is pretty simple so if it were 100 KC there would be a big 100KC
xtal.
That gets replaced with a 60 Khz and away you go.
However I think that switch selects sampling from an input reference so
would thinks its actually 60Khz
Regards
Paul.


On Tue, Jun 25, 2013 at 10:27 PM, Perry Sandeen  wrote:

> List,  There are several Spectracom 8164 receiver available on Ebay.
>
> My question: on the front panel bank of frequency selection switches, the
> left hand switch is marked .1MHz.  Is that really a 100 KHz (for LORAN)
> setting or is it really tuned to WWVB?
>
> If it truly is tuned to 100KHz can it be hacked to 60KHz in a reasonably
> practical manor?
>
> Regards,
>
> Perrier
>
>
>
> 
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Re: [time-nuts] Spectracom 8164 Hack?

[paul swed]

Not sure this went.
Reasonable opens all kinds of doors.
The recvr is pretty simple so if it were 100 KC there would be a big 100KC
xtal.
That gets replaced with a 60 Khz tuning fork and away you go.
However I think that switch selects sampling from an input reference so
would thinks its actually a true 60Khz wwvb rcvr

I am right thats the local reference select they used to use 100KC in radio
stations.

The prices are what can I say silly stupid. Glad someone wants one.
Regards
Paul.




On Tue, Jun 25, 2013 at 10:27 PM, Perry Sandeen  wrote:

> List,  There are several Spectracom 8164 receiver available on Ebay.
>
> My question: on the front panel bank of frequency selection switches, the
> left hand switch is marked .1MHz.  Is that really a 100 KHz (for LORAN)
> setting or is it really tuned to WWVB?
>
> If it truly is tuned to 100KHz can it be hacked to 60KHz in a reasonably
> practical manor?
>
> Regards,
>
> Perrier
>
>
>
> 
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[time-nuts] 60 KHz receivers

[Perry Sandeen]

List, 

On Ebay I stumbled upon a site called pv. electronics from England

The site offers a 60 KHz SYMTRIK Radio Time Receiver
Module W/100 MM Antenna for $25 delivered.  I don't know if this will work with 
Paul Sweed's circuits or not.

It looks like the stuff Digi-Key used to carry made by IIRC C-SPAN.

One can also get modules for the GB and German time transmissions.

HTH someone.

Regards,

Perrier
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[time-nuts] Spectracom 8164 Hack?

[Perry Sandeen]

List,  There are several Spectracom 8164 receiver available on Ebay.

My question: on the front panel bank of frequency selection switches, the left 
hand switch is marked .1MHz.  Is that really a 100 KHz (for LORAN) setting or 
is it really tuned to WWVB?

If it truly is tuned to 100KHz can it be hacked to 60KHz in a reasonably 
practical manor?

Regards,

Perrier




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Re: [time-nuts] OT Prototype Boards

[Chris Albertson]

Your "pi" example does not work.  Pi is not a definition.   the length of
an inch has changed many times over the centuries so there have been many
definitions.  So yes 2.54 mm is the current definition but there are others
and you only have to go mack to 1958 to find that another definition of the
inch was used.

Yes the length of the inch actally changed.  So in theory any ruller or
machine tools or micrometer made in work war II era has been wrong for a
long time.   But fortunately the change was tiny at the 1/10,000th level

The lllength of the inch, foot, yard and so on all changed a little over 50
years ago so that we could have exact and easy conversions to and from the
rest of the world's units.


On Tue, Jun 25, 2013 at 10:52 AM, J. Forster  wrote:

> No. It's THE definition...  there is only one.
>
> It's not like Pi, which equals 3 for small circles.
>
> -John
>
> ===
>
>
>
> > In message
> > 
> > , Robert Darlington writes:
> >
> >>Machinists know that 1 inch is exactly 2.54cm or 25.4mm.  It's a
> >>definition, not a coincidence.
> >
> > The crucial word in that statement being "a" :-)
> >
> > --
> > Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> > p...@freebsd.org | TCP/IP since RFC 956
> > FreeBSD committer   | BSD since 4.3-tahoe
> > Never attribute to malice what can adequately be explained by
> > incompetence.
> > ___
> > time-nuts mailing list -- time-nuts@febo.com
> > To unsubscribe, go to
> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > and follow the instructions there.
> >
> >
>
>
> ___
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> and follow the instructions there.
>



-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] Frequency subtraction with D-flip flops

[EWKehren]

In the Austron 2110 is a dual D FF Mixer along with circuitry to get 100 Hz 
 out. I did a board using 2 XTAL Filter stages and you can get 1 E-12 using 
a 100  MHz period counter. Using my previously mentioned Ping Pong counter 
at 200 MHz  and Offset of 1 Hz at 5 MHz you get 1 Hz out. Resolution is 1 
E-15, there is  some jitter and quite a bit of AV. Presently we use a PTS 40 
to generate the  offset but it will be replaced by an AD9913 DDS. Schmitt 
trigger jitter is not a  problem since the ping pong counter functions like 
time stamp and with two  synchronizing stages does not miss a single count. The 
2 by 2.5 inch board with  out any other additions allows you also to do AV 
measurements as long as one of  the inputs is offset by 1 or 10 Hz.  The DDS 
is a piggy back board and only  is needed if you want to measure frequency 
at high resolution. For AV the board  does every thing.
We plan on using it for long term monitoring using 5/10 Hz out and average  
at least 10 counts. Resolution 1 E-14. Data will be recorded on a USB  
stick.
Key components are a MAX 3000 32 macro G/A two 16F633 PIC's and one 16F688  
PIC output is RS 232. Basically the same board Corby now uses with a few 
more  functions in the G/A.
Bert Kehren
 
 
In a message dated 6/25/2013 4:07:01 P.M. Eastern Daylight Time,  
timen...@binsamp.e4ward.com writes:

(Original seems to have got lost - try again)

> More  recently  we  are  using   two   D   FF's  for  mixing  in A/V
> applications and very  high resolution frequency  measurements with
> up to 1 E-15  a second using output frequencies from 0.5 Hz  to 100
>  Hz.

> Do to attachment limitations if you want more info  contact  me off
> list and I send you some  scans.

> Bert Kehren

Bert,

This  is very interesting. Can you explain in more detail how you can
reach 1e-15 in 1 second with those offset frequencies?

Can you  give the input frequencies, the IC type, and how you measure
the  output?

Thanks

Mike  M
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Re: [time-nuts] OT Prototype Boards

[Magnus Danielson]

Hi Bob,

On 06/25/2013 06:17 PM, Bob Stewart wrote:

Hi Hal,

I had always used 25.4001 or .03937 to do my conversions.  So, I looked online and found 
the .039370078 and did the reciprocal.  It is, indeed very very close to 25.4.  If you 
google "25.4001 conversion" you can find lots of tables using that as the 
conversion factor online.  I don't know where the error came from or why it's quoted so 
regularly.   But, it appears to be the rounded result of taking the reciprocal of a 
rounded number.  Don't machinists use this number for conversion?

Thanks for the discussion, everyone.


US Metric Act from 1866:
www.nist.gov/pml/wmd/metric/upload/HR-596-Metric-Law-1866.pdf
http://lamar.colostate.edu/~hillger/laws/metric-act.html

In 1912 C.E. Johansson decided to use 25.4 mm for one inch (at 20 
degrees C), for his gauge-sets. That was later agreed internationallly 
on in 1933, but the US Metric Act remained unchanged, which caused 
confusion ever since.


Interesting article:
http://www.changeover.com/metrology.html

Anyway, unless you need to use a US Survey feet, 1 inch = 25.4 mm 
exactly is what you should be using.


Cheers,
Magnus
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Re: [time-nuts] OT Prototype Boards

[J. Forster]

It was a JOKE!!!

And, in fact, pi IS a definition: the ratio of the circumferance to the
diameter of a circle - whether it's measured in cubits, furlongs,
nanometers, or light years.

-John

==


> Your "pi" example does not work.  Pi is not a definition.   the length of
> an inch has changed many times over the centuries so there have been many
> definitions.  So yes 2.54 mm is the current definition but there are
> others
> and you only have to go mack to 1958 to find that another definition of
> the
> inch was used.
>
> Yes the length of the inch actally changed.  So in theory any ruller or
> machine tools or micrometer made in work war II era has been wrong for a
> long time.   But fortunately the change was tiny at the 1/10,000th level
>
> The lllength of the inch, foot, yard and so on all changed a little over
> 50
> years ago so that we could have exact and easy conversions to and from the
> rest of the world's units.
>
>
> On Tue, Jun 25, 2013 at 10:52 AM, J. Forster  wrote:
>
>> No. It's THE definition...  there is only one.
>>
>> It's not like Pi, which equals 3 for small circles.
>>
>> -John
>>
>> ===
>>
>>
>>
>> > In message
>> > 
>> > , Robert Darlington writes:
>> >
>> >>Machinists know that 1 inch is exactly 2.54cm or 25.4mm.  It's a
>> >>definition, not a coincidence.
>> >
>> > The crucial word in that statement being "a" :-)
>> >
>> > --
>> > Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
>> > p...@freebsd.org | TCP/IP since RFC 956
>> > FreeBSD committer   | BSD since 4.3-tahoe
>> > Never attribute to malice what can adequately be explained by
>> > incompetence.
>> > ___
>> > time-nuts mailing list -- time-nuts@febo.com
>> > To unsubscribe, go to
>> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> > and follow the instructions there.
>> >
>> >
>>
>>
>> ___
>> time-nuts mailing list -- time-nuts@febo.com
>> To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>
>
>
> --
>
> Chris Albertson
> Redondo Beach, California
>


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Re: [time-nuts] OT Prototype Boards

[Bruce Griffiths]

Chris Albertson wrote:

On Tue, Jun 25, 2013 at 9:17 AM, Bob Stewart  wrote:

   

Hi Hal,

I had always used 25.4001 or .03937 to do my conversions.  So, I looked
online and found the .039370078 and did the reciprocal.  It is, indeed very
very close to 25.4.  If you google "25.4001 conversion" you can find lots
of tables using that as the conversion factor online.  I don't know where
the error came from or why it's quoted so regularly.   But, it appears to
be the rounded result of taking the reciprocal of a rounded number.  Don't
machinists use this number for conversion?
 


Some years ago in 1959 the inch was re-defined to be exactly 25.4 mm.
Before that time the inch was only very close to 24.5 mm  But for the last
50+ years 24.5 has been an exact conversion.

Likely people who are now 65+ years old where taught something different in
school if they were in school befoe 1959 and did not keep up with this.
   
To make it even more interesting there were several "flavours" (US, 
Canadian, UK ...)of the inch which all differed by a very small amount.


Bruce
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[time-nuts] Frequency subtraction with D-flip flops

[Mike M]

  (Original seems to have got lost. Try again)

  > More recently  we  are  using   two   D  FF's  for  mixing  in A/V
  > applications and very high resolution frequency  measurements with
  > up to 1 E-15 a second using output frequencies from 0.5 Hz  to 100
  > Hz.

  > Do to attachment limitations if you want more info contact  me off
  > list and I send you some scans.

  > Bert Kehren

  Bert,

  This is very interesting. Can you explain in more detail how you can
  reach 1e-15 in 1 second with those offset frequencies?

  Can you give the input frequencies, the IC type, and how you measure
  the output?

  Thanks

  Mike M
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Re: [time-nuts] Frequency subtraction with D-flip flops

[Mike M]

  (Original seems to have got lost - try again)

  > More recently  we  are  using   two   D  FF's  for  mixing  in A/V
  > applications and very high resolution frequency  measurements with
  > up to 1 E-15 a second using output frequencies from 0.5 Hz  to 100
  > Hz.

  > Do to attachment limitations if you want more info contact  me off
  > list and I send you some scans.

  > Bert Kehren

  Bert,

  This is very interesting. Can you explain in more detail how you can
  reach 1e-15 in 1 second with those offset frequencies?

  Can you give the input frequencies, the IC type, and how you measure
  the output?

  Thanks

  Mike M
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Re: [time-nuts] OT Prototype Boards

[Hal Murray]

b...@evoria.net said:
> If you google "25.4001 conversion" you can find lots of tables using that as
> the conversion factor online.  I don't know where the error came from or why
> it's quoted so regularly. 

Thanks.  I never would have thought to search for 25.4001.  That's an amazing 
calibration on the quality of information out there on the web.

I still remember 39.37 inches per meter from early school years.  I wonder 
what grade that was.  I don't remember that there were any digits past 39.37 
but neither do I remember that there weren't any more.  I don't remember any 
discussion of accuracy back then.

My guess is that the conversion charts on the web come from somebody starting 
with 39.37 rather than 25.4 and being smart enough to do the arithmetic but 
not sharp enough to understand the accuracy or round-off issues.  I wonder 
how many of them are carried over from before the inch was redefined in 1959 
as compared to starting with 39.37.  You do have to be more than a little 
geeky to pay attention to things like this.  It's under 2 ppm.

My copy of Machinery's Handbook (copyright 1984) says 100 inches is 
2,540.0 mm.  It also says 0.03937 inch/mm and 25.4 mm/inch with no 
discussion of the accuracy.

At the few ppm level you have to pay attention to temperature.  (The wiki 
page on micrometers discusses temperature and they are only good for 0.0001 
inches, 100 ppm.)



-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] tube GPS receivers - delay memory

[Brian Alsop]

No.  I'd say the electronics is several years more advanced.  Not the 
same company.   However, the idea and construction is essentially the same.


73 de Brian/K3KO

On 6/25/2013 18:23, Mike Naruta AA8K wrote:


Could this be one of them Brian?

Mike - AA8K

On 06/24/2013 06:58 AM, Brian Alsop wrote:



Interesting you should mention this.  One summer job had me
working at a company that made acoustic delay line memories.
Interesting beasties. You stuck the data in at one end . The
output was connected back to the input to recirculate the data.
One wound the magnetic wire in a flat rectangular box.   A
torsional mode was used rather than push/pull.  A maximum of
about 50 milliseconds of memory was possible.  A special near
zero temperature coefficient wire was used as the medium.  One
used either return to zero or non-return to zero data formats.
NRZ logic doubled the memory.  Part of the job involved laying
out PCB's by hand for the electronics.  IC's were just coming on
the scene.  RTL logic was the only thing available.  For
military applications "flat packs" were used.  Through hole IC's
were used for everybody else. Interesting that flat packs
disappeared for about 20 years until SMT became the rage.

The company eventually died due to lack of suitable wire and
other memory advances.

Brian





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-
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Version: 2012.0.2242 / Virus Database: 3199/5940 - Release Date: 06/25/13





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Version: 2012.0.2242 / Virus Database: 3199/5940 - Release Date: 06/25/13

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Re: [time-nuts] OT Prototype Boards

[J. Forster]

No. It's THE definition...  there is only one.

It's not like Pi, which equals 3 for small circles.

-John

===



> In message
> 
> , Robert Darlington writes:
>
>>Machinists know that 1 inch is exactly 2.54cm or 25.4mm.  It's a
>>definition, not a coincidence.
>
> The crucial word in that statement being "a" :-)
>
> --
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by
> incompetence.
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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>
>


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Re: [time-nuts] OT Prototype Boards

[Poul-Henning Kamp]

In message 
, Robert Darlington writes:

>Machinists know that 1 inch is exactly 2.54cm or 25.4mm.  It's a
>definition, not a coincidence.

The crucial word in that statement being "a" :-)

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] Measuring speed of light or reproducing a metre

[Poul-Henning Kamp]

In message 
, Jim Palfreyman writes:

>With a 3325B, a 5370B, and other time-nut miscellany, what's the quickest
>way you can come up with to measure the speed of light OR reproduce the
>metre.

Run a couple of meters bare wire across your table, terminate one
end in 50 Ohm and feed the other end with a sharp square-wave.

Hook the 5370B up with two oscilloscope probes and set it to TI mode,
AVG=1000 or so.

Start with both probes the same place, SET REF on 5370B to cancel
out the differential delay of the probes.

Now slide the probes along the wire, record distance between them and
measurements, have student plot them on {white|black}board and you
have a pretty good approximation of speed of light.

Even the most battle-scarred physics-teachers will look astonished,
when you nail the speed of light down on their table like that...

However, the meter you get is not long enough, due to the
lack of vacuum and excess of copper atoms.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] OT Prototype Boards

[Robert Darlington]

Machinists know that 1 inch is exactly 2.54cm or 25.4mm.  It's a
definition, not a coincidence.

-Bob


On Tue, Jun 25, 2013 at 10:17 AM, Bob Stewart  wrote:

> Hi Hal,
>
> I had always used 25.4001 or .03937 to do my conversions.  So, I looked
> online and found the .039370078 and did the reciprocal.  It is, indeed very
> very close to 25.4.  If you google "25.4001 conversion" you can find lots
> of tables using that as the conversion factor online.  I don't know where
> the error came from or why it's quoted so regularly.   But, it appears to
> be the rounded result of taking the reciprocal of a rounded number.  Don't
> machinists use this number for conversion?
>
> Thanks for the discussion, everyone.
>
> bob
>
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Re: [time-nuts] OT Prototype Boards

[Chris Albertson]

Likely you had a very old perf board that was made before the 0.1" spacing
was common.   Back in the vacuum tube days the solder strips had tabs on
3/8" centers and layouts were done on multiples of that.  And then when the
early through hole chips came out they were on 0.1 centers.  And you
couldn't use the 3/16 perf boards.  They likely still make 3/16 boards.
 THey are better for all analog parts where you don't use ICs.

Now days the world has gone "surface mount" and the 0.1 based parts are
looking rather over sized.  Everything is geting smaller and cheaper.


On Mon, Jun 24, 2013 at 9:10 PM, Bob Stewart  wrote:

> I need to get some largish prototype boards for my project.  Has the
> industry standardized on a 0.10" pitch for hole spacing?  IOW, if the ad
> says 2.54mm pitch will I get a board that will fit American chips, or will
> I just get something metric sized for the landfill?  I ask, because I've
> got a prototype board sitting around here someplace that is unusable
> because the pitch isn't quite right.  Needless to say, I'm ordering this
> from ebay from a seller in China or Hong Kong or someplace, points East.
>
> Bob - AE6RV
> ___
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> and follow the instructions there.
>



-- 

Chris Albertson
Redondo Beach, California
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[time-nuts] Piezo

[Electronics and Books]

Found book analysis of piezoelectric devices

https://rapidshare.com/files/4115908681/piezo.pdf
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Re: [time-nuts] OT Prototype Boards

[Chris Albertson]

On Tue, Jun 25, 2013 at 9:17 AM, Bob Stewart  wrote:

> Hi Hal,
>
> I had always used 25.4001 or .03937 to do my conversions.  So, I looked
> online and found the .039370078 and did the reciprocal.  It is, indeed very
> very close to 25.4.  If you google "25.4001 conversion" you can find lots
> of tables using that as the conversion factor online.  I don't know where
> the error came from or why it's quoted so regularly.   But, it appears to
> be the rounded result of taking the reciprocal of a rounded number.  Don't
> machinists use this number for conversion?


Some years ago in 1959 the inch was re-defined to be exactly 25.4 mm.
Before that time the inch was only very close to 24.5 mm  But for the last
50+ years 24.5 has been an exact conversion.

Likely people who are now 65+ years old where taught something different in
school if they were in school befoe 1959 and did not keep up with this.
-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] OT Prototype Boards

[Bob Stewart]

Hi Hal,

I had always used 25.4001 or .03937 to do my conversions.  So, I looked online 
and found the .039370078 and did the reciprocal.  It is, indeed very very close 
to 25.4.  If you google "25.4001 conversion" you can find lots of tables using 
that as the conversion factor online.  I don't know where the error came from 
or why it's quoted so regularly.   But, it appears to be the rounded result of 
taking the reciprocal of a rounded number.  Don't machinists use this number 
for conversion?

Thanks for the discussion, everyone.

bob




- Original Message -
> From: Hal Murray 
> To: Discussion of precise time and frequency measurement 
> Cc: 
> Sent: Tuesday, June 25, 2013 10:53 AM
> Subject: Re: [time-nuts] OT Prototype Boards
> 
> I think many many years ago, the metric-inch conversion was slightly off from 
> 25.4 mm/inch, but that was back before PCBs and it was only off a tiny amount.
> 
> Wikipedia's inch article has a history section:
>   http://en.wikipedia.org/wiki/Inch#Modern_standardisation
> The (a?) old conversion was 39.37 inches/meter.  In 1959, that was changed to 
> 25.4 mm/inch.
> 
> For those of you reading the surveying discussion, there is still a US Survey 
> inch using 39.37.  :)
> 
> 25.4 mm/inch is 39.370078 inches/meter.  That's under 2 ppm from 39.37.  A 
> 50 
> pin connector with 0.1 inch spacing would be off by only 0.001 inch.  You 
> could probably see or measure that if you looked carefully, but I doubt if 
> there would be any problems inserting a part.
> 
> --
> 
> I've never had any problems with 0.1 inch spacing.
> 
> I have seen problems with surface mount parts that were metric at 0.65 or 0.5 
> mm pitch where somebody rounded off too early.  That's easy to do if you 
> look 
> at the drawing and use the inch numbers without realizing that you should be 
> using the metric numbers.
> 
> I just looked at a couple of data sheets.  They omitted the inch numbers for 
> the drawings that were really metric.
> 
> 
> -- 
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Re: [time-nuts] OT Prototype Boards

[MailLists]

That's overstretched... eastern chips worked quite well, similarly to 
western counterparts. Some faulty prototypes could have been distributed 
through the black market, but none would've been incorporated in an 
official product. Even the westerners had bugs...
CCCP, and PRL made intel clones, DDR Zilog, and DEC ones, and NRB 
Motorolas. CCCR also had AMD bit-slice, and DEC clones. RSR was on it's 
"independence" trip, and had built mainly Z80 family chips, but also 
intel support ones.

There were even original developments with no western equivalent.
It was kind of policy that each country specialized in a particular 
segment with minimal overlapping, so that SEV/RGW/CAER/etc. (eng. 
Comecon) countries had to exchange goods.
As for the metric pitch, it was probably more a politically justified 
decision to not use imperial(ist) units.
At least Czechoslovakian, Polish, Bulgarian, and Romanian chips were 
made with .1" pitch. The German, and Russian chips were the "metric" ones.



On 6/25/2013 6:22 PM, Bob Stewart wrote:

Brent,

I seem to remember a story about the early days of micro-computing, when Russia was 
cloning 8080 chips.  Their chips were of such poor quality that each chip had a 
unique list of executions that could not be used.  Anyway, the Russians had sized 
their chip in metric measurements (2.54mm) rather than inches (0.10"), so that 
black market imports of the real thing would not fit.

Bob



- Original Message -

From: Brent Gordon
To: time-nuts@febo.com
Cc:
Sent: Tuesday, June 25, 2013 9:40 AM
Subject: Re: [time-nuts] OT Prototype Boards

I once saw a board that was 2.5 mm, which would cause what you
describe.  As soon as I figured out what the problem was, in the trash
it went.

Brent

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Re: [time-nuts] Measuring speed of light or reproducing a metre

[Chris Albertson]

Earthquakes, yes that range is one of the most active in the world.  They
measure an uplift of as much as 2 inches per year, those mountains are
still getting taller.


On Tue, Jun 25, 2013 at 3:54 AM, Jim Lux  wrote:

> On 6/24/13 6:48 PM, Tom Miller wrote:
>
>> I wonder what the actual distance is using current GPS survey processes?
>>
>> Tom
>>
>>
> SLightly different, because there are some faults running across there and
> there have been some earthquakes with displacement.
>
>
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-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] OT Prototype Boards

[Bob Stewart]

You are right, I was wrong.  The Russian 8080 boards were made with 2.5mm, not 
2.54.




- Original Message -
> From: MailLists 
> To: j...@quikus.com; Discussion of precise time and frequency measurement 
> 
> Cc: 
> Sent: Tuesday, June 25, 2013 10:05 AM
> Subject: Re: [time-nuts] OT Prototype Boards
> 
> In the eastern block the customary pitch was exactly 2.5mm. At least 
> SSSR and DDR ICs were made so. For DIP40s it was a little of a stretch 
> (read pin bending) job to get them fit on .1" spaced boards...
> 
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Re: [time-nuts] OT Prototype Boards

[Hal Murray]

b...@evoria.net said:
> OK, I see in the wiki that 0.1" is by definition 2.54mm.  I was taught it
> was 2.54001, but that's not right, either.  But, if industry says that
> they're defined as the same, then I'm the one out of date.  =)  I wonder
> what was with that old prototype board.  I can't find it, so it must be in a
> landfill, but it was just exactly the wrong size to fit a chip.  You could
> get the first few pins in, but then the differences would be enough that no
> more would fit.

I think many many years ago, the metric-inch conversion was slightly off from 
25.4 mm/inch, but that was back before PCBs and it was only off a tiny amount.

Wikipedia's inch article has a history section:
   http://en.wikipedia.org/wiki/Inch#Modern_standardisation
The (a?) old conversion was 39.37 inches/meter.  In 1959, that was changed to 
25.4 mm/inch.

For those of you reading the surveying discussion, there is still a US Survey 
inch using 39.37.  :)

25.4 mm/inch is 39.370078 inches/meter.  That's under 2 ppm from 39.37.  A 50 
pin connector with 0.1 inch spacing would be off by only 0.001 inch.  You 
could probably see or measure that if you looked carefully, but I doubt if 
there would be any problems inserting a part.

--

I've never had any problems with 0.1 inch spacing.

I have seen problems with surface mount parts that were metric at 0.65 or 0.5 
mm pitch where somebody rounded off too early.  That's easy to do if you look 
at the drawing and use the inch numbers without realizing that you should be 
using the metric numbers.

I just looked at a couple of data sheets.  They omitted the inch numbers for 
the drawings that were really metric.


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] OT Prototype Boards

[MailLists]

In the eastern block the customary pitch was exactly 2.5mm. At least 
SSSR and DDR ICs were made so. For DIP40s it was a little of a stretch 
(read pin bending) job to get them fit on .1" spaced boards...


On 6/25/2013 5:09 PM, J. Forster wrote:

It's not 'industry'. It's the international standards agency, whatever
it's called. The folks that define a meter as some number of wavelengths
of light in vacuo and so on.

There are some early perf boards that have holes on 1/16" centers, for use
w/flea clips'.

-John

===





OK, I see in the wiki that 0.1" is by definition 2.54mm.  I was taught it
was 2.54001, but that's not right, either.  But, if industry says that
they're defined as the same, then I'm the one out of date.  =)  I wonder
what was with that old prototype board.  I can't find it, so it must be in
a landfill, but it was just exactly the wrong size to fit a chip.  You
could get the first few pins in, but then the differences would be enough
that no more would fit.

Bob




- Original Message -

From: Orin Eman
To: Discussion of precise time and frequency measurement

Cc:
Sent: Monday, June 24, 2013 11:35 PM
Subject: Re: [time-nuts] OT Prototype Boards

0.1" is 2.54mm by definition these days.

See: http://en.wikipedia.org/wiki/International_yard_and_pound

Now whether the board really is 2.54mm is an entirely different
matter...
if it is, you should be fine with 0.1" pitch chips.

Orin.



On Mon, Jun 24, 2013 at 9:10 PM, Bob Stewart  wrote:


  I need to get some largish prototype boards for my project.  Has the
  industry standardized on a 0.10" pitch for hole spacing?  IOW, if the

ad

  says 2.54mm pitch will I get a board that will fit American chips, or
will
  I just get something metric sized for the landfill?  I ask, because

I've

  got a prototype board sitting around here someplace that is unusable
  because the pitch isn't quite right.  Needless to say, I'm ordering

this

  from ebay from a seller in China or Hong Kong or someplace, points
East.

  Bob - AE6RV
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Re: [time-nuts] OT Prototype Boards

[Tom Clifton]

With Glass/Epoxy protoboards being so expensive, I have bought several lots of 
a phenolic perf board for prototypes off the web and they have been the most 
inexpensive boards I have ever found.  I don't feel bad about trashing failed 
prototypes..  Search your favorite site for 7x9cm PCB Blank Circuit Board - you 
will find plenty.  Also - I tend to do point-to-point wiring by soldering 30ga 
kynar wire wrap wire to the pads. Silver plated - solders well...  I have an 
old pair of flush cutters with a nick in the blade that works perfectly as a 
wire stripper...
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Re: [time-nuts] OT Prototype Boards

[Bob Stewart]

Brent,

I seem to remember a story about the early days of micro-computing, when Russia 
was cloning 8080 chips.  Their chips were of such poor quality that each chip 
had a unique list of executions that could not be used.  Anyway, the Russians 
had sized their chip in metric measurements (2.54mm) rather than inches 
(0.10"), so that black market imports of the real thing would not fit.

Bob



- Original Message -
> From: Brent Gordon 
> To: time-nuts@febo.com
> Cc: 
> Sent: Tuesday, June 25, 2013 9:40 AM
> Subject: Re: [time-nuts] OT Prototype Boards
> 
> I once saw a board that was 2.5 mm, which would cause what you 
> describe.  As soon as I figured out what the problem was, in the trash 
> it went.
> 
> Brent
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Re: [time-nuts] OT Prototype Boards

[Tom Miller]

Maybe it was a 2 mm pitch, a somewhat common size. Others that come to mind 
are 0.125 and 0.156 inches.


Tom

- Original Message - 
From: "Bob Stewart" 
To: "Discussion of precise time and frequency measurement" 


Sent: Tuesday, June 25, 2013 10:03 AM
Subject: Re: [time-nuts] OT Prototype Boards


OK, I see in the wiki that 0.1" is by definition 2.54mm. I was taught it was 
2.54001, but that's not right, either. But, if industry says that they're 
defined as the same, then I'm the one out of date. =) I wonder what was with 
that old prototype board. I can't find it, so it must be in a landfill, but 
it was just exactly the wrong size to fit a chip. You could get the first 
few pins in, but then the differences would be enough that no more would 
fit.


Bob




- Original Message -

From: Orin Eman 
To: Discussion of precise time and frequency measurement 


Cc:
Sent: Monday, June 24, 2013 11:35 PM
Subject: Re: [time-nuts] OT Prototype Boards

0.1" is 2.54mm by definition these days.

See: http://en.wikipedia.org/wiki/International_yard_and_pound

Now whether the board really is 2.54mm is an entirely different matter...
if it is, you should be fine with 0.1" pitch chips.

Orin.



On Mon, Jun 24, 2013 at 9:10 PM, Bob Stewart  wrote:


 I need to get some largish prototype boards for my project. Has the
 industry standardized on a 0.10" pitch for hole spacing? IOW, if the

ad
 says 2.54mm pitch will I get a board that will fit American chips, or 
will

 I just get something metric sized for the landfill? I ask, because

I've

 got a prototype board sitting around here someplace that is unusable
 because the pitch isn't quite right. Needless to say, I'm ordering

this

 from ebay from a seller in China or Hong Kong or someplace, points East.

 Bob - AE6RV
 ___
 time-nuts mailing list -- time-nuts@febo.com
 To unsubscribe, go to
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Re: [time-nuts] OT Prototype Boards

[Brent Gordon]

I once saw a board that was 2.5 mm, which would cause what you 
describe.  As soon as I figured out what the problem was, in the trash 
it went.


Brent

On 6/25/2013 8:03 AM, Bob Stewart wrote:

OK, I see in the wiki that 0.1" is by definition 2.54mm.  I was taught it was 
2.54001, but that's not right, either.  But, if industry says that they're defined 
as the same, then I'm the one out of date.  =)  I wonder what was with that old 
prototype board.  I can't find it, so it must be in a landfill, but it was just 
exactly the wrong size to fit a chip.  You could get the first few pins in, but then 
the differences would be enough that no more would fit.

Bob


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Re: [time-nuts] OT Prototype Boards

[J. Forster]

It's not 'industry'. It's the international standards agency, whatever
it's called. The folks that define a meter as some number of wavelengths
of light in vacuo and so on.

There are some early perf boards that have holes on 1/16" centers, for use
w/flea clips'.

-John

===




> OK, I see in the wiki that 0.1" is by definition 2.54mm.  I was taught it
> was 2.54001, but that's not right, either.  But, if industry says that
> they're defined as the same, then I'm the one out of date.  =)  I wonder
> what was with that old prototype board.  I can't find it, so it must be in
> a landfill, but it was just exactly the wrong size to fit a chip.  You
> could get the first few pins in, but then the differences would be enough
> that no more would fit.
>
> Bob
>
>
>
>
> - Original Message -
>> From: Orin Eman 
>> To: Discussion of precise time and frequency measurement
>> 
>> Cc:
>> Sent: Monday, June 24, 2013 11:35 PM
>> Subject: Re: [time-nuts] OT Prototype Boards
>>
>> 0.1" is 2.54mm by definition these days.
>>
>> See: http://en.wikipedia.org/wiki/International_yard_and_pound
>>
>> Now whether the board really is 2.54mm is an entirely different
>> matter...
>> if it is, you should be fine with 0.1" pitch chips.
>>
>> Orin.
>>
>>
>>
>> On Mon, Jun 24, 2013 at 9:10 PM, Bob Stewart  wrote:
>>
>>>  I need to get some largish prototype boards for my project.  Has the
>>>  industry standardized on a 0.10" pitch for hole spacing?  IOW, if the
>> ad
>>>  says 2.54mm pitch will I get a board that will fit American chips, or
>>> will
>>>  I just get something metric sized for the landfill?  I ask, because
>> I've
>>>  got a prototype board sitting around here someplace that is unusable
>>>  because the pitch isn't quite right.  Needless to say, I'm ordering
>> this
>>>  from ebay from a seller in China or Hong Kong or someplace, points
>>> East.
>>>
>>>  Bob - AE6RV
>>>  ___
>>>  time-nuts mailing list -- time-nuts@febo.com
>>>  To unsubscribe, go to
>>>  https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>  and follow the instructions there.
>>>
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Re: [time-nuts] OT Prototype Boards

[Bob Stewart]

OK, I see in the wiki that 0.1" is by definition 2.54mm.  I was taught it was 
2.54001, but that's not right, either.  But, if industry says that they're 
defined as the same, then I'm the one out of date.  =)  I wonder what was with 
that old prototype board.  I can't find it, so it must be in a landfill, but it 
was just exactly the wrong size to fit a chip.  You could get the first few 
pins in, but then the differences would be enough that no more would fit.

Bob




- Original Message -
> From: Orin Eman 
> To: Discussion of precise time and frequency measurement 
> Cc: 
> Sent: Monday, June 24, 2013 11:35 PM
> Subject: Re: [time-nuts] OT Prototype Boards
> 
> 0.1" is 2.54mm by definition these days.
> 
> See: http://en.wikipedia.org/wiki/International_yard_and_pound
> 
> Now whether the board really is 2.54mm is an entirely different matter...
> if it is, you should be fine with 0.1" pitch chips.
> 
> Orin.
> 
> 
> 
> On Mon, Jun 24, 2013 at 9:10 PM, Bob Stewart  wrote:
> 
>>  I need to get some largish prototype boards for my project.  Has the
>>  industry standardized on a 0.10" pitch for hole spacing?  IOW, if the 
> ad
>>  says 2.54mm pitch will I get a board that will fit American chips, or will
>>  I just get something metric sized for the landfill?  I ask, because 
> I've
>>  got a prototype board sitting around here someplace that is unusable
>>  because the pitch isn't quite right.  Needless to say, I'm ordering 
> this
>>  from ebay from a seller in China or Hong Kong or someplace, points East.
>> 
>>  Bob - AE6RV
>>  ___
>>  time-nuts mailing list -- time-nuts@febo.com
>>  To unsubscribe, go to
>>  https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>  and follow the instructions there.
>> 
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Re: [time-nuts] OT Prototype Boards

[J. Forster]

2.54 mm is DEFINED as 0.1 inch. The conversion is EXACT.

-John




> 2.54 mm pitch is close enough to the .1 in "standard". The through-hole
> DIP chips will fit fine.  I used to build stuff with .1 in perfboard,
> sockets, and wire-wrap but only use a very few glue chips now and
> pinboards.  They don't have to be shot in rockets . . .
> My only bitch currently is with the absurd gaps in the Arduino boards
> Grr.
> Don
>
>
> Bob Stewart
>> I need to get some largish prototype boards for my project.  Has the
>> industry standardized on a 0.10" pitch for hole spacing?  IOW, if the ad
>> says 2.54mm pitch will I get a board that will fit American chips, or
>> will I just get something metric sized for the landfill?  I ask, because
>> I've got a prototype board sitting around here someplace that is
>> unusable because the pitch isn't quite right.  Needless to say, I'm
>> ordering this from ebay from a seller in China or Hong Kong or
>> someplace, points East.
>>
>> Bob - AE6RV
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> --
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> are as significant as experiment, for thence comes quiet to the mind."
> De Erroribus Medicorum, R. Bacon, 13th century.
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Re: [time-nuts] Frequency subtraction with D-flip flops

[EWKehren]

Forty years ago I did a digital mixer using three J K FF's to subtract the  
IF from the LO for remote monitoring of radio stations. The output is not  
symmetrical but great for a frequency counter. Shortly there after Motorola  
introduced the MC12000 a D FF intended and widely used for PLL 
applications, I  have used it many times. More recently we are using two D FF's 
for  
mixing in A/V applications and very high resolution frequency measurements with 
 up to 1 E-15 a second using output frequencies from .5 Hz to 100 Hz.
Do to attachment limitations if you want more info contact me off list and  
I send you some scans.
Bert Kehren
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Re: [time-nuts] tube GPS receivers

[jmfranke]

For the VCO, how about a reactance modulator. They were very popular for the 
sweeping local oscillator in many a panadapter. Or perhaps one of the voice 
coil based wobbulators?

John  WA4WDL


 Bob Camp  wrote: 
> Hi
> 
> I believe that if you dig into it, the correlator is either running quite 
> fast (in serial mode) or is pretty large (parallel processing). 
> 
> Since you know neither the code nor the doppler (no almanac) you are sweeping 
> both the frequency and the code.
> 
> The VCO is a bit of a challenge (as mentioned earlier). Prior art was 
> basically a motor driven capacitor. Resolution / backlash / dead band are all 
> obvious issues. Not quite so obvious are dead spots in the capacitor it's 
> self and reversals in the tuning characteristic. It's the ratio of the tuning 
> range to the running accuracy that is the driver.
> 
> Bob
> 
> On Jun 24, 2013, at 8:40 PM, Jim Lux  wrote:
> 
> > On 6/24/13 3:01 PM, Bob Camp wrote:
> >> Hi
> >> 
> >> I'm not so sure that "slow" would work. With all the sat's moving various 
> >> directions all the time, I suspect you need to do a solution fairly 
> >> quickly. If you don't the stale data messes up the solution. Also you need 
> >> the correlators to work fast enough to lock on to an essentially unknown 
> >> code before the sat is out of view.
> >> 
> > The sliding correlator is pretty easy, and would lock up quite quickly. 
> > Basically, you need to have a vacuum tube PN generator to generate the 
> > correct Gold/Kasami code for the satellite in question (e.g. you need 32 of 
> > those generators). Each generator has a pair of 10 stage shift registers in 
> > it.  I haven't looked in my copy of Millman and Taub, but I think you could 
> > probably build the shift register with 2*N devices (maybe N tubes, if you 
> > use dual triodes/pentodes, what have you).  There might also be better 
> > choices for the tubes that have some form of latching behavior (thyratrons 
> > maybe..)
> > 
> > You slide the correlator until it locks, and then it automatically also 
> > tracks the doppler of that S/V.  I assume you'd use some sort of early/late 
> > tracker rather than a tau dither. I don't know what you'd use as the VCO, 
> > but there is probably some scheme (after all, FM transmitters existed 
> > before the invention of the Varactor solid state device)
> > 
> > You can track the raw observables (code phase and Doppler) without needing 
> > to do a nav solution at all. And those observables don't change all that 
> > quickly (after all, the Doppler only changes a few kHz during many hours as 
> > the satellite goes from horizon to horizon).
> > 
> > The trick is in how do you get the code phase into your nav algorithm. It's 
> > easy to get a pulse at 1 ms intervals when the code epoch comes by, but you 
> > really want to get a range estimate, and that means figuring out where you 
> > are in the bigger scheme of things. and, then getting that ingested into 
> > whatever computation scheme you're using.
> > 
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Re: [time-nuts] Measuring speed of light or reproducing a metre

[Jim Lux]

On 6/24/13 6:48 PM, Tom Miller wrote:

I wonder what the actual distance is using current GPS survey processes?

Tom



SLightly different, because there are some faults running across there 
and there have been some earthquakes with displacement.



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Re: [time-nuts] tube GPS receivers

[Bob Camp]

Hi

I believe that if you dig into it, the correlator is either running quite fast 
(in serial mode) or is pretty large (parallel processing). 

Since you know neither the code nor the doppler (no almanac) you are sweeping 
both the frequency and the code.

The VCO is a bit of a challenge (as mentioned earlier). Prior art was basically 
a motor driven capacitor. Resolution / backlash / dead band are all obvious 
issues. Not quite so obvious are dead spots in the capacitor it's self and 
reversals in the tuning characteristic. It's the ratio of the tuning range to 
the running accuracy that is the driver.

Bob

On Jun 24, 2013, at 8:40 PM, Jim Lux  wrote:

> On 6/24/13 3:01 PM, Bob Camp wrote:
>> Hi
>> 
>> I'm not so sure that "slow" would work. With all the sat's moving various 
>> directions all the time, I suspect you need to do a solution fairly quickly. 
>> If you don't the stale data messes up the solution. Also you need the 
>> correlators to work fast enough to lock on to an essentially unknown code 
>> before the sat is out of view.
>> 
> The sliding correlator is pretty easy, and would lock up quite quickly. 
> Basically, you need to have a vacuum tube PN generator to generate the 
> correct Gold/Kasami code for the satellite in question (e.g. you need 32 of 
> those generators). Each generator has a pair of 10 stage shift registers in 
> it.  I haven't looked in my copy of Millman and Taub, but I think you could 
> probably build the shift register with 2*N devices (maybe N tubes, if you use 
> dual triodes/pentodes, what have you).  There might also be better choices 
> for the tubes that have some form of latching behavior (thyratrons maybe..)
> 
> You slide the correlator until it locks, and then it automatically also 
> tracks the doppler of that S/V.  I assume you'd use some sort of early/late 
> tracker rather than a tau dither. I don't know what you'd use as the VCO, but 
> there is probably some scheme (after all, FM transmitters existed before the 
> invention of the Varactor solid state device)
> 
> You can track the raw observables (code phase and Doppler) without needing to 
> do a nav solution at all. And those observables don't change all that quickly 
> (after all, the Doppler only changes a few kHz during many hours as the 
> satellite goes from horizon to horizon).
> 
> The trick is in how do you get the code phase into your nav algorithm. It's 
> easy to get a pulse at 1 ms intervals when the code epoch comes by, but you 
> really want to get a range estimate, and that means figuring out where you 
> are in the bigger scheme of things. and, then getting that ingested into 
> whatever computation scheme you're using.
> 
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Re: [time-nuts] Frequency subtraction with D-flip flops

[Tom Van Baak]

Thanks, Bruce, for that wonderful phase meter patent reference. Very 
interesting.

BTW, if any of you are wondering why the patent mentions comparing 10.23 MHz 
(GPS) with a "very accurate" 13.4 MHz, the following paper explains that our 
favorite cesium frequency 9192.631770 MHz / 686 = 13.400... MHz:
http://www.pttimeeting.org/archivemeetings/1992papers/Vol%2024_20.pdf

/tvb

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Re: [time-nuts] Frequency subtraction with D-flip flops

[Bruce Griffiths]

Javier Serrano wrote:

On Tue, Jun 25, 2013 at 4:36 AM, ed breya  wrote:

   

4. It seems to me that whenever fd is much higher than fc (fd>>fc), that
fd could be used instead to trigger the second DFF, which would reduce the
metastability of the first DFF somewhat, and also synchronize the output
signal closer to the edges of fd - but with some metastability from that
too.


 

Clocking the two FFs of a synchronizer with different clock signals will
not work against metastability. When the edges of fd and fc are very close
in time, there is a slight chance that the output of the first FF will be
in a metastable state for some time. By clocking the second FF with fc you
allow for a full (guaranteed) period of fc for that output to stabilize to
a solid '0' or '1'. If you clock the two FFs with two different clock
signals you don't have that guarantee. There should be a big gain to be had
somewhere else to do something like that, but I can't see it. I must say
all my experience is with fc very close to fd in frequency, so maybe I am
missing something about the fd>>fc case.

Cheers,

Javier
   
US patent 6441601 describes using a D flipflop as a phase detector when 
fc>fd.

Fd ~ 13.4Mhz, Fc ~ 10.23MHz
In this case the samples are permuted to achieve the right order of 
phase differences.


I have clocked a 74HC164 with a 5.55MHz fc whilst the D input is 
driven at 10.000 MHz to produce a 110 Hz " beat note".


Bruce
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Re: [time-nuts] Frequency subtraction with D-flip flops

[Javier Serrano]

On Tue, Jun 25, 2013 at 4:36 AM, ed breya  wrote:

>
> 4. It seems to me that whenever fd is much higher than fc (fd>>fc), that
> fd could be used instead to trigger the second DFF, which would reduce the
> metastability of the first DFF somewhat, and also synchronize the output
> signal closer to the edges of fd - but with some metastability from that
> too.
>
>
Clocking the two FFs of a synchronizer with different clock signals will
not work against metastability. When the edges of fd and fc are very close
in time, there is a slight chance that the output of the first FF will be
in a metastable state for some time. By clocking the second FF with fc you
allow for a full (guaranteed) period of fc for that output to stabilize to
a solid '0' or '1'. If you clock the two FFs with two different clock
signals you don't have that guarantee. There should be a big gain to be had
somewhere else to do something like that, but I can't see it. I must say
all my experience is with fc very close to fd in frequency, so maybe I am
missing something about the fd>>fc case.

Cheers,

Javier
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