[time-nuts] NavSync CW46 Module
In the January 2007 issue of Microwaves & RF magazine I see a paragraph or two about a GPS disciplined frequency source. The company is NavSync and the module is part number CW46. The stated price is $176 if you are buying 1000 of them. I don't know what one unit would cost, ($220?) but the price seems very reasonable to me for what it does. As a newbie to this, I would like to read comments as to whether this is a good way to go for an accurate 10MHz source. I'm looking to get +- 1 Hz at 1GHz. Their website is at www.navsync.com. Thanks in advance - Darrell ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
In message <[EMAIL PROTECTED]>, Brooke Clarke writes: >Hi: > >There was a recent incident when a passenger aircraft (maybe Canada) had >to make an emergency landing because of a wrong metric - English >conversion resulted in not enough fuel to get to the destination. Not recent, but famous: The Gimli Glider. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | 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 https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
In a message dated 4/3/2007 19:29:25 Pacific Daylight Time, [EMAIL PROTECTED] writes: An Arianne 5 rocket had to be destroyed with its cargo when it veered off course because of a faulty conversion from English to metric in the guidance software. What a bummer! I hate it when that happens!!! Hi Didier, actually unless there was a second explosion I don't know about, the first Arianne-5 proto-rocket exploded due to a variable parameter overflow (missing saturation check) in a calculation. The conversion problem you mentioned happened on a Mars mission. There was a lengthy and technically detailed report in the German CT' magazine, it said the designer of the routine proved extensively that the routine would never overflow on Arianne 4 due to it's flight configuration, and in fact it never did. He left the company, and the guys who followed just copy-pasted his code into the Arianne 5 flight software were the code did overflow due to missing saturation tests and a different flight configuration. BTW: I didn't expect my email about our strange US units to start such a lengthy discussion on the board... bye, Said ** See what's free at http://www.aol.com. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Hi Brooke, Metric screws are spec'd by major diameter, and the number of mm between the peaks of the threads. English are spec'd by diameter, and the number of threads per inch. A 40TPI screw corresponds to a (1/40) * 25.4 = 0.635 mm pitch. There are standard metric pitches of 0.4, 0.45, 0.5, 0.6, 0.7, 0.8, and 1.0 mm. What you are seeing is probably an M3-0.5, M3-0.6, or an M4-0.7 screw. -Chuck Harris Brooke Clarke wrote: > Hi: > > There was a recent incident when a passenger aircraft (maybe Canada) had > to make an emergency landing because of a wrong metric - English > conversion resulted in not enough fuel to get to the destination. > > Are there metric equivalents to different series of English threads. > For example I recently purchased a tap for 8-40 threads after mistakenly > purchasing a 6-40 tap. Most good hardware stores in the US have 4-40 > taps, dies, various lengths screws and nuts. Although 6-40 and 8-40 are > standard sizes they are not commonly stocked. Are there a a number of > alternative combinations of root diameter and pitch in the metric system? > > Have Fun, > > Brooke Clarke ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
>I have read some weird discussion about measurement units. How about weird units? Velocity in attoparsecs (official SI abbreviation apc) per microfortnight? A standard lecture being a microcentury? http://en.wikipedia.org/wiki/List_of_strange_units_of_measurement LtCol Keith E. Brandt, MD, MPH USAF-NASA Aerospace Medicine Liaison Officer Johnson Space Center, Houston, Texas [EMAIL PROTECTED] Goodbye cruel world that was my home- there's cleaner space out here to roam Put my feet up on the moons of Mars- sit back, relax, and count the stars *This message transmitted with 100% recycled electrons ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Thomas A. Frank wrote: >> Are there actually US people on this list who actually continue to >> advocate the use of non-metric units in their country? Speak up! >> > > Of course. > > >> Well the USA ever go metric? >> > > No. > > >> I find it hard to understand why a country as advanced as the US sticks >> with such an antiquated system. I don't get it. >> > > Once this French fade has run its course, you'll all switch back to > English units. > > Tom Frank, KA2CDK > :-) Didier KO4BB ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
An Arianne 5 rocket had to be destroyed with its cargo when it veered off course because of a faulty conversion from English to metric in the guidance software. What a bummer! I hate it when that happens!!! Didier KO4BB Brooke Clarke wrote: > Hi: > > There was a recent incident when a passenger aircraft (maybe Canada) had > to make an emergency landing because of a wrong metric - English > conversion resulted in not enough fuel to get to the destination. > ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
> Are there actually US people on this list who actually continue to > advocate the use of non-metric units in their country? Speak up! Of course. > Well the USA ever go metric? No. > I find it hard to understand why a country as advanced as the US sticks > with such an antiquated system. I don't get it. Once this French fade has run its course, you'll all switch back to English units. Tom Frank, KA2CDK ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Hi: There was a recent incident when a passenger aircraft (maybe Canada) had to make an emergency landing because of a wrong metric - English conversion resulted in not enough fuel to get to the destination. Are there metric equivalents to different series of English threads. For example I recently purchased a tap for 8-40 threads after mistakenly purchasing a 6-40 tap. Most good hardware stores in the US have 4-40 taps, dies, various lengths screws and nuts. Although 6-40 and 8-40 are standard sizes they are not commonly stocked. Are there a a number of alternative combinations of root diameter and pitch in the metric system? Have Fun, Brooke Clarke w/Java http://www.PRC68.com w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml http://www.precisionclock.com Magnus Danielson wrote: >From: Hal Murray <[EMAIL PROTECTED]> >Subject: Re: [time-nuts] Standards for units >Date: Tue, 03 Apr 2007 17:14:50 -0700 >Message-ID: <[EMAIL PROTECTED]> > > > >>>The US has been metric since 1988, however the continued use of >>>customary units during the indefinitely long transition time is the >>>problem. Fundamentally it seems there is a lack of political will to >>>place a definite cutoff date on the use of customary units. >>> >>> >>I have friends who work in the auto industry. They reported (over 10 years >>ago?) that all new designs are metric. >> >>I wonder how much it would help if GSA gave a serious preference to things >>that were metric? >> >>What's 8.5x11 in metric? >> >> > >An odd-shaped A4ish paper for which there is no propper envelope. > >This fact I had to learn from an American professor that was enligthened when >he came to Sweden. Since then he converted to A4 even in his NYC flat where his >wife mostly lives (there is a downside to being professors at different >universities divided by the atlantic). > > > >>Do we have to convert to A4 too? >> >> > >Preferably. :) > > > >>For real fun, look at bicycle parts. I remember seeing one part that had >>25.4 threads per inch. >> >> > >:) > > > >>What fraction of the military is metric? Do they buy potatoes in kilos or >>pounds? >> >> > >The aviation side certainly have alot of imperial measures. Figures. > >Look at GPS. Certainly metric all the way as far as I have seen. Like all >aviation stuff that part may ofcourse use a mixture. Wonder what nice orbit >errors they would have if they used metric and survey inches as basis. >Hmm 2 ppm would be some 50 m or so. > > > >>>One would have thought that with the advent of computers using the >>>"survey inch" and related units for new surveys would have vanished by >>>now. >>> >>> >>There is probably a lot of legal baggage there. I'll bet they will be one of >>the last holdouts. >> >> > >I wonder just how many metric related laws they would have to write before >all things is metric. There is already a few to go around you know. > >Cheers, >Magnus > >___ >time-nuts mailing list >time-nuts@febo.com >https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > > ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Palfreyman, Jim L wrote: > Are there actually US people on this list who actually continue to > advocate the use of non-metric units in their country? Speak up! > > Well the USA ever go metric? > > As an Australian, why would I care, you may ask? > > Well because of the dominance of the US market, some things can be sold > here using imperial units. My biggest beef is televisions. Some (mainly > CRTs) are sold in cm. Others (plasmas and LCDs) are marketed in inches. > You walk into a shop and you a greeted with dual units. It is terrible! > > The key to making metric work is to completely chuck out the use of > non-metric units. Having to convert is the hard bit. We've been metric > for 35 years and still having to convert from inches to cm because of > the United States is so annoying! > > I find it hard to understand why a country as advanced as the US sticks > with such an antiquated system. I don't get it. Because we like it? Because we can? -Chuck Harris ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
From: Hal Murray <[EMAIL PROTECTED]> Subject: Re: [time-nuts] Standards for units Date: Tue, 03 Apr 2007 17:14:50 -0700 Message-ID: <[EMAIL PROTECTED]> > > > The US has been metric since 1988, however the continued use of > > customary units during the indefinitely long transition time is the > > problem. Fundamentally it seems there is a lack of political will to > > place a definite cutoff date on the use of customary units. > > I have friends who work in the auto industry. They reported (over 10 years > ago?) that all new designs are metric. > > I wonder how much it would help if GSA gave a serious preference to things > that were metric? > > What's 8.5x11 in metric? An odd-shaped A4ish paper for which there is no propper envelope. This fact I had to learn from an American professor that was enligthened when he came to Sweden. Since then he converted to A4 even in his NYC flat where his wife mostly lives (there is a downside to being professors at different universities divided by the atlantic). > Do we have to convert to A4 too? Preferably. :) > For real fun, look at bicycle parts. I remember seeing one part that had > 25.4 threads per inch. :) > What fraction of the military is metric? Do they buy potatoes in kilos or > pounds? The aviation side certainly have alot of imperial measures. Figures. Look at GPS. Certainly metric all the way as far as I have seen. Like all aviation stuff that part may ofcourse use a mixture. Wonder what nice orbit errors they would have if they used metric and survey inches as basis. Hmm 2 ppm would be some 50 m or so. > > One would have thought that with the advent of computers using the > > "survey inch" and related units for new surveys would have vanished by > > now. > > There is probably a lot of legal baggage there. I'll bet they will be one of > the last holdouts. I wonder just how many metric related laws they would have to write before all things is metric. There is already a few to go around you know. Cheers, Magnus ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Converter for Time Signal Reveiver?
> What is it? > http://www.gmat.unsw.edu.au/currentstudents/ug/projects/f_pall/html/s19.html It might be some sort of filter or amplifier for WWV. (Or equivalent down under.) This one shows a recorder that does time stamps. They have to get the time from somewhere. http://www.gmat.unsw.edu.au/currentstudents/ug/projects/f_pall/html/s14.html -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
> The US has been metric since 1988, however the continued use of > customary units during the indefinitely long transition time is the > problem. Fundamentally it seems there is a lack of political will to > place a definite cutoff date on the use of customary units. I have friends who work in the auto industry. They reported (over 10 years ago?) that all new designs are metric. I wonder how much it would help if GSA gave a serious preference to things that were metric? What's 8.5x11 in metric? Do we have to convert to A4 too? For real fun, look at bicycle parts. I remember seeing one part that had 25.4 threads per inch. What fraction of the military is metric? Do they buy potatoes in kilos or pounds? > One would have thought that with the advent of computers using the > "survey inch" and related units for new surveys would have vanished by > now. There is probably a lot of legal baggage there. I'll bet they will be one of the last holdouts. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Palfreyman, Jim L wrote: > Are there actually US people on this list who actually continue to > advocate the use of non-metric units in their country? Speak up! > > Well the USA ever go metric? > > As an Australian, why would I care, you may ask? > > Well because of the dominance of the US market, some things can be sold > here using imperial units. My biggest beef is televisions. Some (mainly > CRTs) are sold in cm. Others (plasmas and LCDs) are marketed in inches. > You walk into a shop and you a greeted with dual units. It is terrible! > > The key to making metric work is to completely chuck out the use of > non-metric units. Having to convert is the hard bit. We've been metric > for 35 years and still having to convert from inches to cm because of > the United States is so annoying! > > I find it hard to understand why a country as advanced as the US sticks > with such an antiquated system. I don't get it. > > > Jim Palfreyman > > ___ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > Jim The US has been metric since 1988, however the continued use of customary units during the indefinitely long transition time is the problem. Fundamentally it seems there is a lack of political will to place a definite cutoff date on the use of customary units. With the supposed current emphasis on SI units in the education system hopefully the use of customary units will vanish with a generation or two. One would have thought that with the advent of computers using the "survey inch" and related units for new surveys would have vanished by now. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Are there actually US people on this list who actually continue to advocate the use of non-metric units in their country? Speak up! Well the USA ever go metric? As an Australian, why would I care, you may ask? Well because of the dominance of the US market, some things can be sold here using imperial units. My biggest beef is televisions. Some (mainly CRTs) are sold in cm. Others (plasmas and LCDs) are marketed in inches. You walk into a shop and you a greeted with dual units. It is terrible! The key to making metric work is to completely chuck out the use of non-metric units. Having to convert is the hard bit. We've been metric for 35 years and still having to convert from inches to cm because of the United States is so annoying! I find it hard to understand why a country as advanced as the US sticks with such an antiquated system. I don't get it. Jim Palfreyman ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] Converter for Time Signal Reveiver?
Hi: What is it? http://www.gmat.unsw.edu.au/currentstudents/ug/projects/f_pall/html/s19.html The Scientific and Mathematical Instruments web page http://www.gmat.unsw.edu.au/currentstudents/ug/projects/f_pall/html/scient_&_math.html is part of the Univ of New South Wales Australia which may be a clue. Have Fun, Brooke Clarke -- w/Java http://www.PRC68.com w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml http://www.precisionclock.com ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Hello to all,
and thank you very much Enrico, a very nice and comprehensive
document.
There is a book on the market (2005) "The Measure of all Things" by
Ken Alder, Free Press New York, translated version in german (2006)
"Das Mass der Welt". It tells on about 500 pages quite precise and
very detailed (based on a lot of original french and other documents)
the long history and big work principally of J.- B.-J. Delambre, P.- F.-A.
Méchain
and J.-J. Lalande fighting for the definition and introduction of the meter
in the 18. century.
Worth to be read I believe.
I like all the discussions on this Time-Nuts platform. Concerning the
relation between inch and meter I thought that the definition
is fixed long time ago.
When the meter was defined to be multiples of the wavelength
of light in vacuum, in 1959, the relationship between inches and
centimeters was redefined to be that one inch is equal to 2.540
centimeters, exactly. The new foot, derived from 1 inch = 2.54 cm
(exactly),
is referred to as the "international foot".
There are a lot of informations about to find in the internet, but to be on the
safe
side I had a look on the NIST homepage:
http://emtoolbox.nist.gov/Faq/Faq.asp#FAQ-Miscellaneous-6
(") Quote:
What is the definition of the meter and the inch?
The inch has always been tied to the meter in the U.S. After the Civil War, the
Surveyor General of the U.S. set the inch as 39.37 inches to the meter. The
British had a yard bar, the Canadians had 25.4 mm per inch,
and the other English speaking nations had chosen one of these or some
variation. They were all close, but not exactly the same. The yard bar was in
fact shrinking. In 1959, a conference attended by the directors of
the National Measurement Institutes from all of the English speaking countries,
those who still used inches, met to standardize the inch. The 25.4 mm per inch
(exactly) was chosen, and since then this is the inch used
by NIST (formerly NBS). Except . . . Yes, there is always an exception.
Surveyors still use the old inch because all of the mountains of measurements
in place defining the positions of everything in the US are in these
inches, and the job of changing them was considered too large a task. So
surveyors still use the surveyor inch, 39.37 inches per meter.
(") End of quote.
and :
http://physics.nist.gov/cuu/Units/meter.html
(") Quote:
...in 1983 the CGPM replaced this latter definition by the following definition:
The meter is the length of the path travelled by light in vacuum during a
time interval of 1/299 792 458 of a second.
Note that the effect of this definition is to fix the speed of light in
vacuum at exactly 299 792 458 m·s-1. The original international prototype of
the meter, which was sanctioned by the 1st CGPM in 1889, is still kept
at the BIPM under the conditions specified in 1889.
(")
End of quote.
As well:
Eric Weisstein's World of Physics
http://scienceworld.wolfram.com/physics/Inch.html
An nonmetric unit of length, originally defined as the lengths of
three "average size" barleycorns laid end-to-end, but now more
rationally defined as 2.54 cm. An older definition no longer used
was 1 meter = 39.37 inches, giving 2.54000508 cm/inch.
Surprisingly, these two conversions are both exact. For details on
the current definition of the inch, see
A Tale of Two Feet OR The Case of The Double Standard - T. J. Keefe
http://physics.ccri.cc.ri.us/keefe/twofeet.htm
Finally, the conversion is finally in a concrete form, as long the speed of
light
in vacuum does not turn out to be not constant ;-)
keep watching the time and units,
regards
Arnold, DK2WT
On Tue, 3 Apr 2007 11:37:16 +0200, Enrico Rubiola wrote:
>Dear all,
>I have read some weird discussion about measurement units.
>There is a wonderful book I come across, by Francois Caldarelli
>You may take a look
>http://rubiola.org/shared/caldarelli.pdf
>then it's up to you
>Best
>Enrico Rubiola
>professor of electronics
>web: http://rubiola.org
>e-mail:[EMAIL PROTECTED]
>FEMTO-ST Institute
>32 av. de l'Observatoire
>25044 Besancon, FRANCE
>voice: +33(0)381.853940 (E.Rubiola)
>voice: +33(0)381.853999 (switchboard)
>fax: +33(0)381.853998
>___
>time-nuts mailing list
>time-nuts@febo.com
>https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
___
time-nuts mailing list
time-nuts@febo.com
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] NTSC specs
Peter Vince wrote: > I can't find the reference :-(I'd love to read that RCA > document if it is available electronically. Hello Peter, While not exactly what you are after, this link may help. http://tinyurl.com/245tjp A couple of years ago, I had great fun playing with the maths, so I could overlay GPS time on both PAL and NTSC video - using only a single 16 MHz xtal for a PIC. Regards, Kiwi Geoff (New Zealand). http://www.geocities.com/kiwi_36_nz/ ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Dear all, I have read some weird discussion about measurement units. There is a wonderful book I come across, by Francois Caldarelli You may take a look http://rubiola.org/shared/caldarelli.pdf then it's up to you Best Enrico Rubiola professor of electronics web:http://rubiola.org e-mail: [EMAIL PROTECTED] FEMTO-ST Institute 32 av. de l'Observatoire 25044 Besancon, FRANCE voice: +33(0)381.853940 (E.Rubiola) voice: +33(0)381.853999 (switchboard) fax:+33(0)381.853998 ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
Now I thought the NTSC frame-rate was reduced so that the line frequency was an exact sub-multiple (1/286) of the sound subcarrier at 4.5 MHz, and hence sidebands of the color subcarrier were equally positioned around the sound carrier. Using exactly 30 Hz frame rate (15750 Hz line rate) would have necessitated increasing the sound subcarrier by 4.5 KHz in order to minimise picture-on-sound interference. My understanding is that whilst this was the most obvious this to do, and the major television manufacturers had no problem with that, one or two minor manufacturers of black-and-white televisions objected vociferously that the new signal would be incompatible with their old televisions, and so the FCC insisted the sound carrier had to remain at 4.5 MHz - a decision everybody in television has regretted ever since! I thought I had learnt the above from the SMPTE NTSC specification 170M, but on re-reading that now, I can't find the reference :-( I'd love to read that RCA document if it is available electronically. Peter Vince (BBC Television, London) >This precise sort of error reminds me of the error that RCA >introduced into the frame rate for NTSC color when they discovered >that the chosen color burst frequency was right on top of a diathermy >machine or something silly like that. They bumped the frame rate down >by exactly 0.1%, creating the 29.97 frames/second that >cinematographers have grown to love to hate. > >There's a volume of the RCA Review that came out in 1953 that is all >about the NTSC color system development process. It's fascinating >reading. Available at your local university library. > > >-- > >--David Forbes, Tucson, AZ >http://www.cathodecorner.com/ ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
This was sent before, but never seemed to get to the net. > It is interesting to look in the front of the International > Critical Tables, an encyclopedic set of books containing detailed > scientific information about 1920. Every nation, (hundreds of them) > had their own units which were used in commerce and trade. > Unfortunately the only access on the net to these tables is blocked > by a pay barrier. > Their are now very few nations hanging out for their own units. > The story I heard about the inch/metre relationship was that during > WW2 there were problems making spare parts for aeroplane engines to > specification, and it was discovered that the French had supplied a > replica standard metre to the bureau of standards of each major > country and that these could be quickly used to standardise > engineering measurements. My version said that 25.4000 mm > per inch was the accepted relationship. > > Clocks were made in Napoleons time with ten hour dials with one > hundred minutes. > > Cheers, > Neville Michie > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
From: David Forbes <[EMAIL PROTECTED]> Subject: Re: [time-nuts] Standards for units Date: Mon, 2 Apr 2007 23:22:24 -0700 Message-ID: <[EMAIL PROTECTED]> > At 9:57 PM -0700 4/2/07, Tom Van Baak wrote: > >> >1/meter/39.37 inches = 0.025400051 meters/inch ... > > > >> The interesting thing is that this result is off by 2.04000 ppm. > >> That's a rather precise error! > >> > >> The calculator I used is here: > >> http://homepage.ntlworld.com/r.howitt/Calculator.htm > > > >David, > > > >There are two ways to compute relative error, depending on > >which one you call the reference. > > > >For extra credit, note your number is actually this cool-looking > >fraction* whose pattern you will immediately recognize. > > > >2.0408163264000128000256000512001024... > > > >/tvb > >http://www.LeapSecond.com > > > >* calculated with: echo "80k .002 999.998 / 10 6 ^ * p" | dc > > > Yes, I had a feeling it was that case, but I didn't bother to chase it too > far. > > This precise sort of error reminds me of the error that RCA > introduced into the frame rate for NTSC color when they discovered > that the chosen color burst frequency was right on top of a diathermy > machine or something silly like that. They bumped the frame rate down > by exactly 0.1%, creating the 29.97 frames/second that > cinematographers have grown to love to hate. We *STILL* suffer from this. With CCIR-601 we where doing good, everything about PAL and NTSC joins in with 27 MHz as a common frequency, but when they went for HD-SDI they broke things bigtime as they chose to have 11/2 times higher rate than SD-SDI. So now we have to support 1.485 Gb/s AND 1.485 / 1.001 Gb/s. Sigh! I would have settled for 5 or 6 times instead, that 11 is what breaks the magic. This 1.001 error is a major headache since you can't use the same crystal and pull it either way. If you do many channels it is infeasable to have multiple crystals and choose between them (we have done that once already) and the resynthesis chips doesn't have godo enought phase noise to be useable when they do the 1.001 term. It also shows up in sample-rates, so we see things like 44056 Hz samplings etc. It is still broken and its a PINA to get fixed. (Sorry for the strong wording) > There's a volume of the RCA Review that came out in 1953 that is all > about the NTSC color system development process. It's fascinating > reading. Available at your local university library. Somehow I doubt that. :P Would like to read it thought. Cheers, Magnus ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
James Cloos wrote: >> "David" == David Dameron <[EMAIL PROTECTED]> writes: >> > > David> (I was taught that 1 meter was 39.37 inches, to define the > David> inch, but now I see more of 1 inch = 2.54 cm, as someone just > David> referred to.) > > That was the old inch. It was changed back around 1954 or so. They > decided they didn't want to have an SI unit looking like it was > defined in terms of a legacy unit, and so changed from 1 meter = 39.37 > inches to 1 inch = .0254 meters so that the inch was defined in terms > of the meter. > > Or, as likely, from 1 meter = 3937/1200 feet to 1 foot = .3048 meters. > > The old length is still used for so called survey feet in the US. > > Many conversion routines -- including unix's units(1) and HP's line of > RPL calculators -- call them US feet. > > -JimC > Jim The change occurred in July 1959. At which time the UK, USA, NewZealand etc officially adopted the new definition of the inch. Canada had adopted it somewhat before this. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Standards for units
From: Chuck Harris <[EMAIL PROTECTED]> Subject: Re: [time-nuts] Standards for units Date: Mon, 02 Apr 2007 22:09:49 -0400 Message-ID: <[EMAIL PROTECTED]> Chuck, > > The other inch defined by > > > > 1 inch = 25.4mm exactly > > > > is used for everything else. > > My recollection when I posted the earlier letter was 24.5 mm/inch was > exact by definition, and I recalled that 39.37 inches/meter was also > exact... a quick calculator check to 6 figures showed that it was exact, > then I tried to 9 figures, and saw that pesky little 0.00051. I was telling you that it was of by about 2 ppm. > > For confirmation read the appendix C of NIST Handbook 44, where these > > and other units of measurement are described. > > Why on earth one has to have different units all called barrels for oil, > > cranberry juice, dried fruits, liquor (this one varies from state to > > state) etc., defies imagination. > > I think the biggest push for metric is the chance to start fresh. But > when metric includes piezes, and poises, and sthenes and steres and stokes... > I guess it ain't all that fresh. Huh? Where did you get that from? Cheers, Magnus ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
