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Discussion in 'Electrical Engineering' started by [email protected], Feb 26, 2008.

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  1. Guest

    | Point is, no matter how well you know the precision of one factor (sqrt(3)),
    | if the other factor is only known to two or three significant digits, any
    | product of the two can really only be known to two or three significant
    | digits.

    That is true. Just be careful not to add to the error of the lack of
    precision by prematurely reducing the precision of the well defined
    constant. Otherwise the product ends up with more error than either
    of the multiplicands.

    120 * 1.7320508075688772935274463415058723669428052538103806280558 = 208

    Of course, this example is extreme precision. This is not a boundary case.
    If it were a boundary case, a precise value of the square root of three
    enough to avoid the boundary issue, would be wise to use. I typically use
    more precision than just 1.732. If I have to type in this value by hand,
    I use 1.732050807568877 because I have that much memorized, unless I feel
    lazy in which case I just go with 1.7320508 :)


    |> Back when I was in junior high school, without the aid of any calculator
    |> or computer, I pondered the meaning of the frequency 3.58 MHz as it
    |> related
    |> to the TV broadcast standards (which at the time I "knew" to be 15,750 Hz
    |> horizontal and 60 Hz vertical. But I found a book in the school library
    |> that gave the value as 3.579545 MHz. Just that much information allowed
    |> me to "reverse engineer" this number to determine it came from 5 MHz times
    |> 63 divided by 88, and really had "454545" repeated (3579545.45[45..] Hz),
    |> and that the horizontal frequency was really 15734.265734[265734..] Hz,
    |> and that the vertical frequency was really 59.940059[940059..] Hz.
    |
    | But with all your 'refinements', you're still starting from '5 MHz'. And
    | just how accurate is the 5 MHz crystal considering the ambient temperature
    | of the crystal is pretty much uncontrolled? At the broadcast studio, I'm
    | sure their's are more precise. But the one in the TV set? If I'm not
    | mistaken, that's why they use a PLL circuit.
    |
    | You've assumed the '5 MHz' is exact, and therefore the 3.58 MHz is wrong.
    |
    | Why couldn't it have been.....
    |
    | 5,000,634.92063 Hz * 63/88 = 3,580,000 Hz

    Or 5,047,213.114754 Hz * 61/86 = 3,580,000 Hz

    The thing is, none of these had any particular meaning. But once I had
    that value of 3,579,545 Hz, the resultant 4,999,999.365 became a lot more
    relevant. Then it became clear that the value most likely came from the
    exact 5 MHz reference. For a while, though, I called it 315 MHz / 88.


    | (see, you're not the only one with an arbitrary precision calculator :)

    There are plenty around. Knowing how to use them correctly can elude some.


    | You're not trying to blow smoke and claim that the color burst frequency in
    | an old TV is derived from multiplying 5,000,000.000 Hz times exactly 63/88
    | ??? Like to see the analog circuit that produces such exact multiplication.
    | Sure wasn't in my old RCA set that I tore into a couple of times :)

    No. The _definition_ is. It might be more practical, if you wanted to
    produce it from a WWV locked oscillator, to use 15 MHz * 21 / 88.
    A cheap receiver only needs to be close enough to get a lock and stay
    stable enough to keep the color reasonably consistent. A broadcaster
    didn't even need to, as getting a crystal in an oven to stay within 10 Hz
    of 14318181.818 Hz would good enough. It could be tested or calibrated
    by doing a phase comparison at 315 MHz between the the 21st harmonic of
    15 MHz and the 22nd harmonic of 14.318181818 MHz.


    |> Do you do any computer programming? If so, do you just add up a long
    |> list of floating point values in the order given, or do you sort them
    |> so you accumulate the sum by adding the lowest values first?
    |
    | Yes I do quite a bit of programming thank you very much. Since most
    | floating point numbers are already an inexact representation of 'real'
    | numbers, they can be inherently flawed (hint, use 'doubles', there are more
    | significant digits). Yes, you point out correctly (as anyone who has
    | studied "Numerical Methods" can tell you) that when adding floating point
    | values of widely different decades, the exact order of operations can have
    | an effect on the exact outcome. In general, the more floating operations
    | you go through, the fewer and fewer significant digits you can rely on.
    |
    | That's why there are BCD and 'arbitrary precision' techniques.
    |
    | By the way, if you use something other than base 10 for your fractional
    | representation (or base 2 as used in IEEE-754 floating point format), you
    | can represent some numbers more precisely.

    Indeed. I have used base 16 for that, as well as scaling numbers to get
    all the digits I want to have as integers.

    And I use the GMP package in my Mandebrot fractal program to take my zooms
    to extreme levels.


    |
    |>
    |> How many digits do you want for the square root of three expressed as a
    |> ratio of two integers with a precision in digits equal to or greater than
    |> the SUM of the digits in the numerating AND denominator?
    |>
    |> Anyone can just say:
    |> 17320508075688772935274463415058723669428052538103806280558069794519330169088
    |> divided by:
    |> 10000000000000000000000000000000000000000000000000000000000000000000000000000
    |> but that is only 77 digits of precision for 154 digits expressed.
    |>
    |> But if I give you:
    |> 81637354237035839875406774706916734691676867556988461166524491402570869800626
    |> divided by
    |> 47133348444681477624409145446409554706879415291771528507046516487702731598175
    |> then you can be sure you have 154 digits of precision. Try it.
    |>
    |> Remember 355/113 for the value of PI? I have way better fractions. You
    |> won't _need_ them, of course. But I have them.
    |>
    |
    | But again, you can take as much precision of a mathematically defined value
    | as you want. When you multiply / divide it into something that is measured
    | to only two significant digits and try to claim the result is 207.8461 and
    | is 'more accurate' than 208, you've wasted a lot of everyone's time.

    I use 208 or 207.846 or 207.84609690826527522329356 for different purposes.


    | To claim....
    | 120 * sqrt(3) = 207.8461
    |
    | Is pure nonsense. You cannot possibly improve upon the accuracy of the
    | original measurement. Yet that is what this sort of statement is claiming.
    | "I measured the voltage to the nearest ten volts (120), and thus I know the
    | accuracy of the line-line wye voltage to the nearest ten-thousandth of a
    | volt (207.8461)."

    I disagree ... depending on the context of use. If the multiplication is
    done to an actually measured value, I'll keep the product at the same level
    of precision as the measured value (as scaled by the multiplication).

    123 * sqrt(3) = 213

    123.1 * sqrt(3) = 213.2


    | Now, if you had said....
    |
    | 120 * sqrt(3) = 207.8461 plus or minus 17.3205
    |
    | I would agree with that. And everyone would see that the 'answer' is not
    | that well known (could range from about 190 to 220). But look at what all
    | your 'accuracy' has accomplished.

    Plus or minus 10 in the original measurement, if that is a measurement
    by a voltmeter, is not that accurate at all. That voltmeter sucks.

    OTOH, that could well be the allowable range of the voltage provided by
    a utility or derived from a generator. So:

    120 +/- 10 * sqrt(3) = 207.8460969 +/- 17.32050808

    But at that point, given in definition accuracy, precision in the final
    expression really is pointless. So:

    120 +/- 10 * sqrt(3) = 208 +/- 17

    Still, in cases where I would have to calculate the values, I would use
    a lot of digits of sqrt(3), well more than the measured L-N voltage, then
    round the L-L voltage.


    | I see this a lot when doing unit conversions as well. If you go to a
    | definitive source for the conversion from one set of units to another,
    | you'll find that some conversion factors are given as *exact*, while others
    | are approximations to some number of significant digits. For example, an
    | inch is defined by NIST as *exactly* 25.4 mm. So a foot is *exactly* 304.8
    | mm or 0.3048 m. But 1 meter is only *approximately 3.28083989501 feet.

    The numeric base system we use and/or the units of measure we use do have
    an impact. It is basically a quantization effect. Given the same level
    of meter accuracy, but instead, doing the work in base 2 instead of base
    10, changes things "a round a bit".
     
  2. Guest

    |
    | |> | daestrom wrote:
    |> |
    |> |> Most of us skimp on the rules a bit, but taking a number like 120 *
    |> |> sqrt(3) and claiming the answer to seven significant digits is over the
    |> |> top.
    |> |>
    |> |> daestrom
    |> |> I told you I was going to be pendantic .... :)
    |> |
    |> | I took the P.E. exam before there were hand calculators, so we all used
    |> | slide rules. One advantage was they were perfectly suited for
    |> | engineering work without ever needing to be pedantic. ;-)
    |> |
    |> | I've seen more measurements screwed up by lack of knowledge than by
    |> | insufficient number of decimal places.
    |>
    |> Using the wrong formula can do that.
    |>
    |
    | In many engineering fields (outside of electronics), it's also easy to use
    | the wrong engineering units. Or use the inverse of the conversion from one
    | to another. ;-)
    |
    | Some 'units-phobics' proclaim how metric is so much easier than our (the US)
    | units of measurements. But in actuality, it's just that you can still get
    | the right answer a lot of times because the conversion factors are often
    | just 1. For example, Push with a force of 12 Newtons for a distance of 30
    | meters over a period of 10 seconds. How many Watts? Play around for a
    | minute or so and you can come up with 12*30/10 = 36. But in actuality, one
    | is converting Newton-meters to Joules (1) and Joules/sec to Watts (1).

    Now if only they would just get the rest of the time units metrificated to
    powers of 10 ... 1 day is 86.4 kiloseconds.

    I remember in the mid 1970's I saw a TV PSA (because I was working at a TV
    station at the time ... master control op) that promoted metrification.
    They showed a bunch of different symbols of things they claimed were already
    metric. They showed a clock as one of them I and I noted that was not
    correct.


    | 12 Newtons * 30 meters / 10 seconds * [(1 Joule) / (1 Newton-meter)] * [(1
    | Watt-second) / (1 Joule)] = 36 Watt
    |
    | This is all to often forgotten in the simplicity of just ignoring the
    | conversion factors (because they're always '1').

    Yes, I would agree. The units are quite well correlated. If we just
    learn it this way, though, I think it works well.


    | In US units, if the problem is 'Push with a force of 12 lbf for a distance
    | of 30 feet over a period of 10 seconds, how many horsepower?', you have to
    | actually understand the system of units, and how to apply them.
    |
    | 12 lbf * 30 feet / 10 seconds * [(1 hp) / (550 ft-lbf/s)] = 0.065 horsepower
    |
    | In a way, our system of units, because it is so bizarre, helps teach us to
    | follow through with the units and understand the relationship between force,
    | distance, time and power.

    But I think the metric system makes more sense. We just have to learn
    the simplicity of it in a different way. it would certainly be hard for
    someone accustomed to having to always apply a non-unity conversion.
    I'm glad we didn't have a different set of imperial units for volts, amps,
    watts, ohms, henries, farads, etc.


    | (note: I did *not* say 0.065455 horsepower :)

    :)
     
  3. Roy

    Roy Guest

    From:
    You have a machine that requires 240 volt three phase power. It requires
    connection to 3 phase lines and ground, but not neutral. You ask your
    utility to supply 240 volt delta and they say no. The machine fails to
    operate on 208 volts. What do you do? How many different solutions could
    you think of to explore?
    |---------------------------------------/

    Quick Response:
    Move to a better city or town immediately & bring your business with
    you.

    Elaborated Response:
    This is a trick question, because you cannot have a 3phase 240 without a
    neutral & ground from the utility.,[1 leg of the 3 phase must be a
    neutral] unless your in podunk....The 240, or as it's most commonly know
    220 machine will work fine with 2 phases and no neutral or ground.,
    though you can ground it to your water intake pipe... no one uses 208
    anymore and utility companies do not supply it., only perhaps in
    podunk., or if you are tapping from a private transformer in an
    electrical supply room of some sort.

    In this case you plotted involving a machine & a 220/240VAC supply -
    it'll work whether 3 or 2 phase., I don't think your machine will notice
    the missing phase as long as the 240 VAC potential difference excists
    between the poles to your machine & it will work well.....

    Roy Q.T. ~ US/NCU ~ E.E. Technician
    [have tools, will travel]
     
  4. Guest

    | writes:
    |
    |>It depends on the context. If I am doing a calculation that _should_
    |>come up with the same value as 120 volts times the square root of three,
    |>but want to just express the result value to let someone else match it,
    |>I will use more digits. Usually 6 is enough to not just identify the
    |>system, but identify that the calculation did more than just get into
    |>the right ball park.
    |
    | But then the lady a mile up the road flips on a nightlight, causing the MV
    | voltage to sag a tiny bit, and your 120.00000000 volts is no longer that,
    | so the zillion digit precision calculation of the line-line voltage
    | is no longer accurate...

    If I had a meter that could measure RMS voltage to an accuracy and precision
    of 1/100000000 volt, I'm more likely to curse the noise on the power line.

    I don't use more precision on _measured_ values than the meansurement allows
    for. It's when dealing with _definitions_ of values that more precision
    will be used. The definition has as much accuracy as you want. It is the
    expression of it that has precision.


    |>| daestrom
    |>| I told you I was going to be pendantic .... :)
    |
    |>Back when I was in junior high school, without the aid of any calculator
    |>or computer, I pondered the meaning of the frequency 3.58 MHz as it related
    |>to the TV broadcast standards (which at the time I "knew" to be 15,750 Hz
    |>horizontal and 60 Hz vertical. But I found a book in the school library
    |>that gave the value as 3.579545 MHz. Just that much information allowed
    |>me to "reverse engineer" this number to determine it came from 5 MHz times
    |>63 divided by 88, and really had "454545" repeated (3579545.45[45..] Hz),
    |>and that the horizontal frequency was really 15734.265734[265734..] Hz,
    |>and that the vertical frequency was really 59.940059[940059..] Hz. All
    |
    | As I understood it, the 3.579545 figure was deliberately chosen so to NOT
    | be a multiple of either the V or H frequency, or the audio offset frequency
    | so that the color signal would not interfere with/be interfered with any
    | of the other signals, and 3.579545 was THE definition. Certainly there
    | were tons of dirt-cheap crystals of that frequency (and 14.31818 MHz),
    | no reason to divide down 5 MHz frequency. That number of digits made
    | perfect sense in the definition since crystals could be cut to VERY
    | precise frequencies (and in receivers were PLL'ed to the transmitter)
    | Also, there was a common chip that divided the colorburst frequency down
    | to 60 Hz (intended to use a common cheap crystal as a time base for digital
    | clocks). In order to work correctly the colorburst xtal had to really be
    | 3.579540 MHz. (it divided by 59659)

    Yes, it is true the value was chosen to avoid integer relations to the
    vertical and horizontal frequency. It was also chosen so that sidebands
    of the horizontal modulated on the color would not hit the center of the
    audio subcarrier at +4.5 MHz.

    You can read the definition of the color subcarrier freqyency in the FCC
    rules. If the frequency was chosen without that definition in mind, then
    it is very amazing coincidence.

    The _definition_ does not mean that the frequency has to actually be
    derived from 5 MHz in implementations. The definition is a basis for
    testing the implementation in some way, or calibrating it.


    |>semantically, I need a much more precise value. Would you recognize it
    |>as the NTSC color subcarrier frequency if I called it 3.6 MHz? or 4 MHz?
    |
    | As the definition was to a very high standard that was also met in real
    | life, 3.579545 MHz is the correct term, as a TV whose color frequency
    | was running at 3.6 MHz or 4 MHz (or even 3.58 MHz) would not display
    | colors correctly at all!

    Such oscillators could be pulled in to sync at the arriving frequency.
    But the further away their non-sync frequency is, the less stable they
    will be. If your crystal is cut for 3.579545 and the broadcaster is
    sending 3.579545454545454545 then the circuit will syncronize it.


    |>Do you do any computer programming? If so, do you just add up a long
    |>list of floating point values in the order given, or do you sort them
    |>so you accumulate the sum by adding the lowest values first?
    |
    | I do computer programming and would add the numbers in the order given.
    | If the required precision of the result exceeded that of the computer's
    | "float" precision, I'd use "double" (or higher) and add in the order given.

    If the scale of the numbers is large, and the count of numbers is also
    large, the inaccuracy of such addition could become significant.
     
  5. Guest

    | From:
    | You have a machine that requires 240 volt three phase power. It requires
    | connection to 3 phase lines and ground, but not neutral. You ask your
    | utility to supply 240 volt delta and they say no. The machine fails to
    | operate on 208 volts. What do you do? How many different solutions could
    | you think of to explore?
    | |---------------------------------------/
    |
    | Quick Response:
    | Move to a better city or town immediately & bring your business with
    | you.
    |
    | Elaborated Response:
    | This is a trick question, because you cannot have a 3phase 240 without a
    | neutral & ground from the utility.,[1 leg of the 3 phase must be a

    Transformers with a 139 volt secondary (definition being 240 divided by
    the square root of 3, which works out in high precision to 138.5640646)
    could be used to make a 240Y/139 system. Then deliver the service of
    this without the neutral wire, suitable only for delta loads. Then
    you don't actually have a neutral wire in the service, yet it has a
    definit ground voltage relationship.


    | neutral] unless your in podunk....The 240, or as it's most commonly know
    | 220 machine will work fine with 2 phases and no neutral or ground.,
    | though you can ground it to your water intake pipe... no one uses 208
    | anymore and utility companies do not supply it., only perhaps in
    | podunk., or if you are tapping from a private transformer in an
    | electrical supply room of some sort.

    208Y/120 is still quite common. It is specified in virtually all tariffs
    (all that I have read, anyway).

    If you are getting 220 volts line to line from a wye system, you are
    getting 127 volts line to neutral/ground.
     
  6. Guest

    | wrote:
    |>
    |> I don't use more precision on _measured_ values than the meansurement allows
    |> for. It's when dealing with _definitions_ of values that more precision
    |> will be used. The definition has as much accuracy as you want. It is the
    |> expression of it that has precision.
    |
    |
    | Bullshit. Adding more than an extra digit or two to the
    | specification gains you absolutely nothing, other a than a complete
    | waste of your time.

    When a measurement is inaccurate, a reduction in precision does little
    more than encapsulate thet inaccuracy. The error is still the same.

    When you multiply two values with a range of error, that range of error
    increases to accomodate the extremes.

    If you multiply a measured value (which has some error) by a defined
    value with a reduced precision (that's error, too), that increases the
    error.

    But I take it you don't care.

    BTW, the amount of _my_ time that increases to do the extra digits is
    extremely small. I have much practice in doing it. Maybe you don't.


    |> Yes, it is true the value was chosen to avoid integer relations to the
    |> vertical and horizontal frequency. It was also chosen so that sidebands
    |> of the horizontal modulated on the color would not hit the center of the
    |> audio subcarrier at +4.5 MHz.
    |>
    |> You can read the definition of the color subcarrier freqyency in the FCC
    |> rules. If the frequency was chosen without that definition in mind, then
    |> it is very amazing coincidence.
    |
    |
    | Sigh. The reasons are VERY well laid out in older TV design
    | handbooks. Maybe a little reading will open your eyes?

    Are you talking about before or after color?

    I've read the books. I wonder if you ever did.


    |> The _definition_ does not mean that the frequency has to actually be
    |> derived from 5 MHz in implementations. The definition is a basis for
    |> testing the implementation in some way, or calibrating it.
    |
    |
    | The 5 MHz reference was chosen, because it was generally available at
    | the transmitter site to verify the frequency.

    You certainly can derive the color subcarrier frequency from 5 MHz if you
    want to (or from 15 MHz). But whether that readily available 5 MHz is
    used to directly derive the color subcarrier frequency or is merely used
    to calibrate an oscillator tuned to the color subcarrier frequency, my
    point is still the same.


    |> Such oscillators could be pulled in to sync at the arriving frequency.
    |> But the further away their non-sync frequency is, the less stable they
    |> will be. If your crystal is cut for 3.579545 and the broadcaster is
    |> sending 3.579545454545454545 then the circuit will syncronize it.
    |
    |
    | Phil, quit being a complete and total asshole. No station has the
    | ability to measure that far, and the FCC rounds it to the nearest full
    | digit, plus or minus 10 Hz. Because of this, the frequency is measured
    | to the spec, plus one extra digit to minimize random changes. Believe
    | me, it takes long enough to zero the master crystal in a sync generator,
    | or frame store that once it is within one hertz of the spec, you stop.
    | it will drift up and down a few cycles, even in an oven.

    Why is it that people like you always have to make personal attacks instead
    of just arguing the applicable points you disagree with?

    I already said the FCC requires it be plus or minus 10 Hz.


    | Yes, you can play with your calculations all you want, but its just a
    | total waste of time, like almost everything else you post. Even IF the
    | color burst DID happen to drift to fall exactly on your ridiculous set
    | of numbers, the TV set still wouldn't be exactly on frequency, because
    | the seven cycles of color burst are used to pull the frequency close to,
    | but not exactly to 3.579545 MHz. I should know. I was responsible for
    | a 5 MW EIRP UHF TV transmitter, not a 'master control operator' who
    | signed the form and got that pretty little certificate that acknowledged
    | that the FCC knew I existed. Hell, we had a young hippy flower child who
    | pulled third shift as a master control operator at one time. She didn't
    | even know ohm's law, but she was excellent at filling out the log, and
    | watching for problems. She was on the phone to the engineers the second
    | something wasn't right, if one of the engineers wasn't on site.

    If you think my posts are a waste of time, then I have a suggestion for
    you ... don't read them anymore. Then you'll not feel any need to post
    a followup and waste even more time.

    I've never said that one subcarrier burst would be syncronize a local
    oscillator to exactly the frequency the transmitter is using. But with
    many bursts, as long as the local oscillator is not so far off as to be
    a half-horizontal frequency displacement, it will _accumulate_ the same
    exact number of cycles. That will center the spectral energy around
    the transmitter's subcarrier frequency. The closer that local oscillator
    is tuned to the correct frequency, the narrower the energy band will be.
    That means a more stable oscillator and better color.

    Neither being responsible for a transmitter, nor being a master control
    operator, means you necessarily will understand how an oscilator under
    syncronization will behave and produce a complex waveform. Maybe if you
    read up more on radio theory ... where you could design a transmitter
    instead of just flip them on and replace bad tubes ... then maybe you
    would "get it".
     
  7. Guest

    |
    |>|>>
    |>>>Do you do any computer programming? If so, do you just add up a long
    |>>>list of floating point values in the order given, or do you sort them
    |>>>so you accumulate the sum by adding the lowest values first?
    |>>
    |>> I do computer programming and would add the numbers in the order given.
    |>> If the required precision of the result exceeded that of the computer's
    |>> "float" precision, I'd use "double" (or higher) and add in the order
    |>> given.
    |>>
    |
    |>Well, the point that 'phil-news' was trying to make is that sometimes just
    |>adding in the order given can cause some problems. If the first has a value
    |>that is so much larger than the second that the second has to be shifted 24
    |>bits to the right before adding, then its value is lost (in 'single
    |>precision' IEEE-754 format, 24 bits are used for the mantissa).
    |
    | I know. My point was that if the order of addition affected the answer
    | enough to affect the outcome (at the needed precision), you simply need
    | more bits of precision in the variables. Like going from 24 bit "float"
    | to "double". Otherwise there will be some combination of inputs that will
    | bite you hard with the wrong answer.

    Given that you have a finite precision to work with, sorting the values from
    smallest to largest is the most practical way. If infinite precision does
    happen to be available, then you can use that.
     
  8. Guest

    | wrote:
    |>
    |> | wrote:
    |> |>
    |> |> I don't use more precision on _measured_ values than the meansurement allows
    |> |> for. It's when dealing with _definitions_ of values that more precision
    |> |> will be used. The definition has as much accuracy as you want. It is the
    |> |> expression of it that has precision.
    |> |
    |> |
    |> | Bullshit. Adding more than an extra digit or two to the
    |> | specification gains you absolutely nothing, other a than a complete
    |> | waste of your time.
    |>
    |> When a measurement is inaccurate, a reduction in precision does little
    |> more than encapsulate thet inaccuracy. The error is still the same.
    |>
    |> When you multiply two values with a range of error, that range of error
    |> increases to accomodate the extremes.
    |>
    |> If you multiply a measured value (which has some error) by a defined
    |> value with a reduced precision (that's error, too), that increases the
    |> error.
    |>
    |> But I take it you don't care.
    |>
    |> BTW, the amount of _my_ time that increases to do the extra digits is
    |> extremely small. I have much practice in doing it. Maybe you don't.
    |>
    |> |> Yes, it is true the value was chosen to avoid integer relations to the
    |> |> vertical and horizontal frequency. It was also chosen so that sidebands
    |> |> of the horizontal modulated on the color would not hit the center of the
    |> |> audio subcarrier at +4.5 MHz.
    |> |>
    |> |> You can read the definition of the color subcarrier freqyency in the FCC
    |> |> rules. If the frequency was chosen without that definition in mind, then
    |> |> it is very amazing coincidence.
    |> |
    |> |
    |> | Sigh. The reasons are VERY well laid out in older TV design
    |> | handbooks. Maybe a little reading will open your eyes?
    |>
    |> Are you talking about before or after color?
    |
    |
    | Both. The library at Cincinnati Electronics had all the books from
    | the original Crosley engineering department, along with all of the IRE
    | and IEEE papers on Television, and covered every system that was
    | presented to the FCC, and ALL of the test results.

    So there are books that talk about why the particular frequency was chosen
    for the color subcarrier, before there was color?


    |> I've read the books. I wonder if you ever did.
    |
    |
    |
    | Sigh. No. of course not, you dumb ass. No one but you has ever read
    | them. They were written just so you could show off to everyone. That's
    | why i have a nice collection in my personal library. I always spend
    | lots of money on books I don't read.

    At least you are being honest. I have only one book that deals with TV
    technology. The rest I have read from the library.


    |
    |
    |> |
    |> |
    |> | The 5 MHz reference was chosen, because it was generally available at
    |> | the transmitter site to verify the frequency.
    |>
    |> You certainly can derive the color subcarrier frequency from 5 MHz if you
    |> want to (or from 15 MHz). But whether that readily available 5 MHz is
    |> used to directly derive the color subcarrier frequency or is merely used
    |> to calibrate an oscillator tuned to the color subcarrier frequency, my
    |> point is still the same.
    |
    |
    | 5 and or 10 MHz have been the in house reference for decades. The
    | first frequency counters acceptable for TV use were built with ovenized
    | oscillators that produced at least one of these frequencies. The most
    | common counter was the HP 5245L with the proper front end plug in.

    And?


    |> |> Such oscillators could be pulled in to sync at the arriving frequency.
    |> |> But the further away their non-sync frequency is, the less stable they
    |> |> will be. If your crystal is cut for 3.579545 and the broadcaster is
    |> |> sending 3.579545454545454545 then the circuit will syncronize it.
    |> |
    |> |
    |> | Phil, quit being a complete and total asshole. No station has the
    |> | ability to measure that far, and the FCC rounds it to the nearest full
    |> | digit, plus or minus 10 Hz. Because of this, the frequency is measured
    |> | to the spec, plus one extra digit to minimize random changes. Believe
    |> | me, it takes long enough to zero the master crystal in a sync generator,
    |> | or frame store that once it is within one hertz of the spec, you stop.
    |> | it will drift up and down a few cycles, even in an oven.
    |>
    |> Why is it that people like you always have to make personal attacks instead
    |> of just arguing the applicable points you disagree with?
    |
    |
    | Why is it people like you, who have NEVER done the work talk down to
    | those who have?

    What work? Have you _designed_ a complete TV encoding and transmission
    system from the ground up? Can you even do the Fourier transforms (among
    other things), needed to understand the signals and spectrum energy needed
    to make the design effective?


    |> I already said the FCC requires it be plus or minus 10 Hz.
    |
    |
    | You also said that it was +/- 10 Hz at 14.318180 MHz, when it is +/-
    | 40 Hz

    The FCC requirement of +/- 10 Hz is for the on-air subcarrier. Do the
    math to figure out what it needs to be for other frequencies you might
    derive the subcarrier from.


    |> If you think my posts are a waste of time, then I have a suggestion for
    |> you ... don't read them anymore. Then you'll not feel any need to post
    |> a followup and waste even more time.
    |
    |
    | If someone doesn't call you on your bullshit and blunders, then the
    | people who have no clue will think that you are right.

    If you think I do that, then be specific and to the point. There is no
    need to make personal attacks. You have done that a lot, as have a small
    handful of others on Usenet. One of them even posts here a lot.


    |> I've never said that one subcarrier burst would be syncronize a local
    |> oscillator to exactly the frequency the transmitter is using.
    |
    |
    | You stated that it would be pulled to whatever the burst frequency
    | was.

    But I did not say that one burst alone would do that. You implied that
    I did and that was wrong on your part.


    |> But with
    |> many bursts, as long as the local oscillator is not so far off as to be
    |> a half-horizontal frequency displacement, it will _accumulate_ the same
    |> exact number of cycles. That will center the spectral energy around
    |> the transmitter's subcarrier frequency. The closer that local oscillator
    |> is tuned to the correct frequency, the narrower the energy band will be.
    |> That means a more stable oscillator and better color.
    |
    |
    | You really have no clue, do you? In most burst circuits, more that
    | two cycles difference, and it will not be pulled to the subcarrier
    | frequency. Do you have a studio grade sync generator, a broadcast
    | quality waveform monitor, or a broadcast grade vectorscope?

    You seem to be the one with no clue.

    Two cycles difference of what? Or do you mean 2 Hz? Well, I have news
    for you ... an oscillator that would naturally oscillate at 2 Hz from
    the transmitted signal can be pulled to that signal. Sure, it will
    slip between burst pulses. But at 2 Hz difference, it's not that much.
    It would be about 0.04576 degrees of phase by the time the next burst
    comes along. You wouldn't even notice the color shift from left to
    right.


    |> Neither being responsible for a transmitter, nor being a master control
    |> operator, means you necessarily will understand how an oscilator under
    |> syncronization will behave and produce a complex waveform. Maybe if you
    |> read up more on radio theory ... where you could design a transmitter
    |> instead of just flip them on and replace bad tubes ... then maybe you
    |> would "get it".
    |
    |
    | That old ham radio smugness is showing, Phil. I built and rebuilt TV
    | transmitters, and one entire TV station from an empty building. The only
    | tubes in the last transmitter were EEV Klystrons that cost $45,000 each,
    | and produced 65 KW of RF. Have you ever worked with one of those? How
    | about repairing a video effects unit with a three phase 208 input, and a
    | 1000A 5.00 VDC output power supply? All work had to be done hot. All
    | the signals had to be adjusted to under a half degree phase shift, or it
    | was visible, on air. Have you ever stood inside a TV transmitter, on
    | the plate supply wile it's on the air to make an emergency repair? have
    | you spent a half hour centering the range of the transmitter's LO so it
    | centers perfectly around the center frequency? How about
    | troubleshooting and repairing studio cameras between live shots? You
    | think highly of yourself, and you don't know shit.

    I did not ask if you built. By father has built lots of electronic stuff
    and he has zero clue how any of it works. Just because your stuff costs
    a lot more only shows you are probably a lot more careful following the
    directions to the letter.

    But can you _design_ an NTSC encoding system? I have.


    | Also, have you ever tried to match a set of 16 6146 tubes for a
    | distributed video amplifier for the video modulator stage on a 1950's
    | RCA TTU25B transmitter? It can take days, and a couple hundred tubes to
    | select a set from. You don't just stick a tube in a TV transmitter and
    | expect it to work properly. In fact, I wrote an improved service manual
    | for the gates transmitters we used at the AFRTS station I was assigned
    | to. I could generally get back on the air in under two minutes, then
    | fine tune everything. The biggest problem I had was a station manager
    | with a ham radio license who kept moistening the transmitter, and
    | compressing the sync. The idiot couldn't grasp the difference between
    | his Swan SSB rig and a broadband TV transmitter. You don't tune a TV
    | transmitter for peak power, it has to be aligned with test equipment to
    | have a flat video response.

    No I have not matched a set of 16 6146 tubes. This relates to understanding
    the color subcarrier how?


    | Have you ever built a communications system for the ISS? Selectable
    | bandwidths to 40 Mbps, and it allowed audio, video and data transfer at
    | the same time? No. While you are busy playing with a calculator, SOME
    | of us were actually doing real work in the RF world.

    There's plenty of real work that involves not knowing anything about
    waveforms, signals, or even mathematics. It obviously shows from some
    of the errors you've made in posts that you think you are so great
    because you've have your hands on all this stuff. But you couldn't
    create a mathematical model for how it works.
     
  9. Guest

    | writes:
    |
    |>|
    |>| I know. My point was that if the order of addition affected the answer
    |>| enough to affect the outcome (at the needed precision), you simply need
    |>| more bits of precision in the variables. Like going from 24 bit "float"
    |>| to "double". Otherwise there will be some combination of inputs that will
    |>| bite you hard with the wrong answer.
    |
    |>Given that you have a finite precision to work with, sorting the values from
    |>smallest to largest is the most practical way. If infinite precision does
    |>happen to be available, then you can use that.
    |
    | If the order of the addition makes a difference in the results, then it is
    | a violation of the associative law of addition, so the addition isn't
    | being done properly. This is due to insufficient precision being used.
    | It is then an engineering decision whether higher precision must be used
    | or if the effect can be ignored (introduced error falls well within the
    | range of measurement or calculation errors or whatever) For example if
    | you were calculating power consumption of multi kW heaters and tried to
    | include the effect of the lady switching on a nightlight and its MV droop
    | effect.

    Adding a small number to a large number requires more precision than either
    alone needs to be expressed. What the order of addition does is allow that
    dynamic to work in your favor. Sure, it is right to have enough precision
    to do the addition. But you do have that enough precision in a dynamic
    way when the addition is done from smallest to largest, without having to
    expend the effort on more precise addition properties to achieve it.
     
  10. Guest

    | wrote:
    |>
    |> |> | Sigh. The reasons are VERY well laid out in older TV design
    |> |> | handbooks. Maybe a little reading will open your eyes?
    |> |>
    |> |> Are you talking about before or after color?
    |> |
    |> |
    |> | Both. The library at Cincinnati Electronics had all the books from
    |> | the original Crosley engineering department, along with all of the IRE
    |> | and IEEE papers on Television, and covered every system that was
    |> | presented to the FCC, and ALL of the test results.
    |>
    |> So there are books that talk about why the particular frequency was chosen
    |> for the color subcarrier, before there was color?
    |
    |
    | Yes, ones printed during the development and the deployment of
    | color. They went into great detail about the problems expected, and the
    | changes needed to prevent them.
    |
    |
    |> |> I've read the books. I wonder if you ever did.
    |> |
    |> |
    |> |
    |> | Sigh. No. of course not, you dumb ass. No one but you has ever read
    |> | them. They were written just so you could show off to everyone. That's
    |> | why i have a nice collection in my personal library. I always spend
    |> | lots of money on books I don't read.
    |>
    |> At least you are being honest. I have only one book that deals with TV
    |> technology. The rest I have read from the library.
    |
    |
    | Once again, sarcasm goes right over your head.

    Who's sarcasm is the more subtle, eh?


    |> | 5 and or 10 MHz have been the in house reference for decades. The
    |> | first frequency counters acceptable for TV use were built with ovenized
    |> | oscillators that produced at least one of these frequencies. The most
    |> | common counter was the HP 5245L with the proper front end plug in.
    |>
    |> And?
    |
    |
    | And what? Either ask a question or shut up, troll.

    How does what you said apply? Why don't you connect it to what was being
    talked about?


    |> | Why is it people like you, who have NEVER done the work talk down to
    |> | those who have?
    |>
    |> What work? Have you _designed_ a complete TV encoding and transmission
    |> system from the ground up? Can you even do the Fourier transforms (among
    |> other things), needed to understand the signals and spectrum energy needed
    |> to make the design effective?
    |
    |
    | Phil, some people are intuitive, and can see how things work. Others
    | need a pencil to take a crap.

    You also need some paper with that pencil.


    |> |> I already said the FCC requires it be plus or minus 10 Hz.
    |> |
    |> |
    |> | You also said that it was +/- 10 Hz at 14.318180 MHz, when it is +/-
    |> | 40 Hz
    |>
    |> The FCC requirement of +/- 10 Hz is for the on-air subcarrier. Do the
    |> math to figure out what it needs to be for other frequencies you might
    |> derive the subcarrier from.
    |
    |
    | I did. You are the one who claimed it was still +/- 10 Hz at
    | 14.318180 MHz

    Fine, whatever you say.


    |> If you think I do that, then be specific and to the point. There is no
    |> need to make personal attacks. You have done that a lot, as have a small
    |> handful of others on Usenet. One of them even posts here a lot.
    |
    |
    | Did you ever think that they are doing because you are wrong?

    Did you ever think that maybe you ought to just point out specifically
    what you think is wrong, when someone posts something you think is wrong,
    and include what you think is right? And do that post as a direct
    followup to the specific post that has what you think was wrong.


    |> | You really have no clue, do you? In most burst circuits, more that
    |> | two cycles difference, and it will not be pulled to the subcarrier
    |> | frequency. Do you have a studio grade sync generator, a broadcast
    |> | quality waveform monitor, or a broadcast grade vectorscope?
    |>
    |> You seem to be the one with no clue.
    |
    |
    | So, you have never looked at what your design is capable of? That is
    | exactly what I expected

    Why would I have broadcast grade studio equipment at home?


    |> Two cycles difference of what? Or do you mean 2 Hz? Well, I have news
    |> for you ... an oscillator that would naturally oscillate at 2 Hz from
    |> the transmitted signal can be pulled to that signal. Sure, it will
    |> slip between burst pulses. But at 2 Hz difference, it's not that much.
    |> It would be about 0.04576 degrees of phase by the time the next burst
    |> comes along. You wouldn't even notice the color shift from left to
    |> right.
    |
    |
    | Ok. sure. yeah.
    |
    |
    | You have no clue, phil. The chroma would change from the left to the
    | right side of the screen if the burst oscillator isn't closer to the
    | expected frequency. You don't think so, but I've worked with several
    | video directors who could see that across the room. The burst is used
    | to fine tune the phasing, and the tint control is used to manually trim
    | it. It sets the center frequency, and if you were right, there would be
    | no way to set the tint.

    Yes it would change. I never said it would not. But I did the calculations
    and the amount of change (0.04576 degrees of phase) is so small it would
    most likely not even make a one bit difference if the resultant color was
    digitized.

    Maybe you are talking about an oscillator that is off way more than 2 Hz?


    | What directions? A lot of components were obsolete, and very little
    | documentation had survived over the years. I had schematics, and parts
    | lists with RCA stock numbers, but RCA was out of the broadcast
    | business. It required thinking on your feet, and being able to redesign
    | some stages to work. Tell me where you would find a RF component that
    | hadn't been built in 20 years, and the old one was burnt beyond
    | recognition? What would you do if some dumb ass had brazed the custom
    | made brass fittings in the cooling circuit to the copper pipe, over some
    | bad solder. Without them, the transmitter was scrap.

    And did you have to do math? Vector math? Trig? I wonder what part
    you would have failed at if you had been called on to do it.


    | Small potatoes. Have you designed an FQPSK encoding system, and the
    | decoding system? Hell, I've designed and built test fixtures that were
    | more complex. NTSC encoders were done with a handful of tubes and a
    | delay line for the sync. have you ever designed video amps with a 3 dB
    | point at 40 MHz, and less than .5 dB ripple over the entire pass band?

    And yet you don't know how many degrees of phase change take place between
    two sine waves only 2 Hz apart in frequency over the time a one video line?


    | I suppose you'll be bragging abut designing buggy whips, too? The
    | large semiconductor manufacturers have obsoleted their NTSC chipsets,
    | because of HDTV. No one will be designing any new NTSC encoders. Have
    | you designed and built a low phase noise synthesizer to track deep space
    | probes? It operated in three adjacent segments to cover 370 MHz to 520
    | MHz continuous. All the math in the world wouldn't predict all the
    | quirks in a design like that. A lifetime of experience does. Simple
    | things, like changing from an uncased disk capacitor to a SMD part of
    | better quality caused the phase noise to shoot through the roof. All
    | the math in the world wouldn't explain it, but being VERY familiar with
    | RF PC board design made it obvious. Something that the other engineers
    | overlook, because they had no hands on experience with that design. The
    | large Vias that had been used to mount the uncased ceramics had to be
    | filled, all the way to prevent them from being low value inductors in
    | the ground plane.

    Sure, experience helps. But getting math wrong can still destroy any
    design project.


    |> No I have not matched a set of 16 6146 tubes. This relates to understanding
    |> the color subcarrier how?
    |
    |
    | Phil, you don't understand much of anything. If that distributed
    | amplifier isn't balanced, the chroma doesn't get to the modulator. The
    | burst was the highest frequency passed by the video amplifier, and
    | mismatched tubes cause a loss of response at the higher frequencies, and
    | some phase shift.

    So if those 16 tubes are not perfectly matched, no signal gets out at
    all? Maybe you need a whole different approach.

    Why are you using 6146 tubes to pass chroma? Oh, wait, you didn't design
    this.


    |> There's plenty of real work that involves not knowing anything about
    |> waveforms, signals, or even mathematics. It obviously shows from some
    |> of the errors you've made in posts that you think you are so great
    |> because you've have your hands on all this stuff. But you couldn't
    |> create a mathematical model for how it works.
    |
    |
    | So, you would spend month reinventing hundreds of wheels, rather than
    | use what you already know? I went through the paper and pencil math
    | phase at around 13 years old, but I'VE outgrown it. A mathematical
    | model doesn't do any work. A piece of working equipment does. Your
    | models don't deal wth real world issues, only what would be in a perfect
    | universe. We designed and built $80,000 telemetry receivers without all
    | your excessive math, and they worked so well that we couldn't keep up
    | with the orders for a year or more. How many multi-million dollar
    | contracts do you get from your anal retentive math?

    Based on the math you've show you can do, I don't want to be anywhere near
    those hazards.
     
  11. Guest

    |> Why would I have broadcast grade studio equipment at home?
    |
    |
    | To prove your design. That is, unless you're a clueless hack.

    I'm not making designs of broadcast equipment. I'm explaining bits of
    the math that should be used in such a design. Spending the money on
    such equipment to prove anything to you is not worth it. You are not
    worth it.

    And clearly it is not worth even posting to you, because you are so
    closed minded about technology. So I guess I'll stop soon.


    |> And did you have to do math? Vector math? Trig? I wonder what part
    |> you would have failed at if you had been called on to do it.
    |
    |
    | i know, you're a "Just Spice It" type.

    See, you really do make up things.


    |> | Small potatoes. Have you designed an FQPSK encoding system, and the
    |> | decoding system? Hell, I've designed and built test fixtures that were
    |> | more complex. NTSC encoders were done with a handful of tubes and a
    |> | delay line for the sync. have you ever designed video amps with a 3 dB
    |> | point at 40 MHz, and less than .5 dB ripple over the entire pass band?
    |>
    |> And yet you don't know how many degrees of phase change take place between
    |> two sine waves only 2 Hz apart in frequency over the time a one video line?
    |
    |
    | It depends on the burst circuit. they are not all created equally.
    | Early tube circuits wouldn't lock properly. modern, solid state will
    | lock over a wider range. you haven't specified anything other than you
    | like to do math, which doesn't take into account the subtle variations
    | in the real world. Typical of those with a glass belly button.

    If it has the correct number of cycles over the long term (a second)
    then it is in sync. If the number of cycles is different, it is not
    in sync (and you'll have a funny pattern of changing colors).


    |> Sure, experience helps. But getting math wrong can still destroy any
    |> design project.
    |
    |
    | getting the math right can lead you down false trails without the
    | proper experience.

    You need both.


    |> |> No I have not matched a set of 16 6146 tubes. This relates to understanding
    |> |> the color subcarrier how?
    |> |
    |> |
    |> | Phil, you don't understand much of anything. If that distributed
    |> | amplifier isn't balanced, the chroma doesn't get to the modulator. The
    |> | burst was the highest frequency passed by the video amplifier, and
    |> | mismatched tubes cause a loss of response at the higher frequencies, and
    |> | some phase shift.
    |>
    |> So if those 16 tubes are not perfectly matched, no signal gets out at
    |> all? Maybe you need a whole different approach.
    |>
    |> Why are you using 6146 tubes to pass chroma? Oh, wait, you didn't design
    |> this.
    |
    |
    | i didn't say i did. It was a early '50s RCA design. My job was to
    | dismantle a dead transmitter, move it several hundred miles, and make it
    | work again. No support from RCA was available, so i had to take an
    | existing design with almost no documentation and make it meet FCC
    | specifications again. I did all the math with a TI pocket calculator.

    I bet all those extra digits on that calculators was scary to you.


    | Not a problem. You could never get the proper security clearance to
    | enter the sites where they are used. NASA, NOAA, the European Space
    | Agency and other government agencies had no problems with the design, so
    | whatever you think of it isn't worth a plugless nickel. They don't
    | launch anything at the cape without our products. Another product they
    | use are 'command destruct receivers', but I would think they are about
    | out of them, by now.

    The government buys lots of junk that can't do the job right. Why is your
    junk any different?
     
  12. Guest

    | Once again, you'll get inaccurate results because both the error margin in
    | the large number exceeds the value of any of the small numbers, and the

    You don't know what the error margin is in this area of discussion because
    it has not been specified. It might be high or it might be low. But either
    of the correct ways to add numbers (with enough precision to handle the full
    dynamic range from the smallest to largest ... or by sorting the numbers to
    accumulate the sum smallest first to largest last) does not in and of itself
    introduce any new error. It may well be far more precise than is necessary
    for a given data set that has error in it. But in cases where the smaller
    numbers exceed the absolute error of the larger numbers, the smaller numbers
    are all noise no matter what you do.


    | order of operations affects the outcome. Also, adding the small numbers
    | first isn't necessarily the best step. Consider when you have to sum an
    | array of numbers where two are nearly equal in magnitude, which is large,
    | but opposite in sign. The rest are small, smaller than the error in
    | either large number. If you add the small numbers first then add in one
    | of the large magnitude numbers, you'll lose many digits of precision.

    Of course you will, if the precision of the add is less than the full scale
    of large and small number together. It is presumed you use addition with
    enough precision for your needs in the sum. If the sum of all small numbers
    is still so small it gets lost when the next number is very large, then so
    be it. What the sorted summation method does is give those small numbers
    that may have been lost BY THEMSELVES the opportunity to have the sum of
    the small numbers make it into the level of precision the addition is using.


    | Add in the other large number and you have a sum of similar magitude to
    | the small numbers but with substantial loss of precision. On the other
    | hand, if you add the large numbers first, you'll have a smallish sum where
    | adding the other small numbers makes sense.

    If you have two large numbers, one positive and one negative, and your level
    of precision is such that the small numbers would not add in to either of
    these large numbers, then you would not have these large numbers represented
    with enough precision to get a sum that had a significance on the scale of
    the smaller numbers.

    This could well argue that you do need mucho precision in the arithmetic.
    But if the end result only needs a certain level of precision, then all
    those small numbers are unimportant and these two large numbers add up to
    zero and that is the correct result in that case.


    | Once again, if you are faced with such a situation, you'll have to either:
    | 1) use higher precision variables (double vs. float for example);
    | 2) decide that the smaller numbers fall within the margin of error and
    | should be disregarded; or
    | 3) Find a better way.

    Again, adding sorted numbers works. There certainly are cases where the sum
    of all the small numbers does not make it into the final sum. But that is
    not a case of incorrect calculation; it is just a case where they were all
    too insignificant to affect the final sum. This all presumes the precision
    of the additions is enough for the final result. If that is not the case,
    all hope is lost.


    | By 3) I'll use this as an example: You have an empty dump truck and you
    | know its weight, and you need to know the gross weight of a full truck.
    | The truck scale used to weigh the truck can measure to what? 100 pounds?
    | 10 pounds? You can measure the mass of each grain of sand to the
    | nearest billionth of a gram. Do you:
    |
    | 1) Weigh each grain of sand, add the weights and finally add the weight of
    | the truck?
    | 2) Ignore the weight of the sand (after all, the weight of each grain is
    | much smaller than the error in the weight of the truck)?
    | 3) Do something else, say weigh each scoop of sand as a front end
    | loader loads the truck, or just weigh the full truck?
    |
    | You are arguing that 1) is the best solution. I claim it's absurd, and I
    | suspect most will agree. 2) isn't correct either, as a trip across a
    | bridge with a weight restriction will show. In this case "something else"
    | is the best choice.

    Don't mix up the methods of measurement with the methods of arithmetic. Your
    example involves measurement process. That is an entirely different thing.


    | The correct choice is an engineering situation that depends on the
    | situation.

    Are you saying this about measurement? Or about calculation?
     
  13. Guest

    | wrote:
    |>
    |>
    |> |> Why would I have broadcast grade studio equipment at home?
    |> |
    |> |
    |> | To prove your design. That is, unless you're a clueless hack.
    |>
    |> I'm not making designs of broadcast equipment. I'm explaining bits of
    |> the math that should be used in such a design. Spending the money on
    |> such equipment to prove anything to you is not worth it.
    |
    |
    | Bullshit. You don't know what you're talking about, as usual. Try
    | spouting your igonrance on and they'll ter
    | you a new asshole. Thn you'll have three.

    There's no ignorance in what I say. If there was, anyone who wanted to
    point it out would have been specific and said exactly what was wrong.
    No one did. A couple of jerks (you being one of them) came along to take
    pot shots because they have some serious attitude problems. That's all
    it is.
     
  14. Guest

    | wrote:
    |>
    |> | wrote:
    |> |>
    |> |>
    |> |> |> Why would I have broadcast grade studio equipment at home?
    |> |> |
    |> |> |
    |> |> | To prove your design. That is, unless you're a clueless hack.
    |> |>
    |> |> I'm not making designs of broadcast equipment. I'm explaining bits of
    |> |> the math that should be used in such a design. Spending the money on
    |> |> such equipment to prove anything to you is not worth it.
    |> |
    |> |
    |> | Bullshit. You don't know what you're talking about, as usual. Try
    |> | spouting your igonrance on and they'll ter
    |> | you a new asshole. Thn you'll have three.
    |>
    |> There's no ignorance in what I say. If there was, anyone who wanted to
    |> point it out would have been specific and said exactly what was wrong.
    |> No one did. A couple of jerks (you being one of them) came along to take
    |> pot shots because they have some serious attitude problems. That's all
    |> it is.
    |
    |
    | Ok, if it floats your boat, Phil. Believe that you're the only one in
    | the world who is right. Haven't you noticed that no one is backing you
    | up? A sane person takes that into consideration.

    You actually think anyone else is following this thread?
     
  15. Guest

    | wrote:
    |>
    |> | wrote:
    |> |>
    |> |> | wrote:
    |> |> |>
    |> |> |>
    |> |> |> |> Why would I have broadcast grade studio equipment at home?
    |> |> |> |
    |> |> |> |
    |> |> |> | To prove your design. That is, unless you're a clueless hack.
    |> |> |>
    |> |> |> I'm not making designs of broadcast equipment. I'm explaining bits of
    |> |> |> the math that should be used in such a design. Spending the money on
    |> |> |> such equipment to prove anything to you is not worth it.
    |> |> |
    |> |> |
    |> |> | Bullshit. You don't know what you're talking about, as usual. Try
    |> |> | spouting your igonrance on and they'll ter
    |> |> | you a new asshole. Thn you'll have three.
    |> |>
    |> |> There's no ignorance in what I say. If there was, anyone who wanted to
    |> |> point it out would have been specific and said exactly what was wrong.
    |> |> No one did. A couple of jerks (you being one of them) came along to take
    |> |> pot shots because they have some serious attitude problems. That's all
    |> |> it is.
    |> |
    |> |
    |> | Ok, if it floats your boat, Phil. Believe that you're the only one in
    |> | the world who is right. Haven't you noticed that no one is backing you
    |> | up? A sane person takes that into consideration.
    |>
    |> You actually think anyone else is following this thread?
    |
    |
    | Obviously you are. Tell me something, Phil. Do you ever watch the
    | news and see either weather satellite photos, or NASA's live video feeds
    | from space?

    Of course I am ... I started the thread.

    Why don't you ask that question in a thread you start. I don't see how
    that even connects to this thread.
     
  16. Guest

    | wrote:
    |>
    |> |
    |> | Obviously you are. Tell me something, Phil. Do you ever watch the
    |> | news and see either weather satellite photos, or NASA's live video feeds
    |> | from space?
    |>
    |> Of course I am ... I started the thread.
    |>
    |> Why don't you ask that question in a thread you start. I don't see how
    |> that even connects to this thread.
    |
    |
    | Of course you don't, but that great video is received with the
    | equipment you dammed in another message. The designs you called

    Maybe if there was another design, you would have received the messages
    even more reliably. Of course, if the design that is chosen works,
    there would be no incentive to improve on it. Why spend money doing
    a whole new better design if the poor design now in use accomplishes
    the goals anyway.
     
  17. Guest

    | wrote:
    |>
    |> | wrote:
    |> |>
    |> |> |
    |> |> | Obviously you are. Tell me something, Phil. Do you ever watch the
    |> |> | news and see either weather satellite photos, or NASA's live video feeds
    |> |> | from space?
    |> |>
    |> |> Of course I am ... I started the thread.
    |> |>
    |> |> Why don't you ask that question in a thread you start. I don't see how
    |> |> that even connects to this thread.
    |> |
    |> |
    |> | Of course you don't, but that great video is received with the
    |> | equipment you dammed in another message. The designs you called
    |>
    |> Maybe if there was another design, you would have received the messages
    |> even more reliably. Of course, if the design that is chosen works,
    |> there would be no incentive to improve on it. Why spend money doing
    |> a whole new better design if the poor design now in use accomplishes
    |> the goals anyway.
    |
    |
    | You still don't get it. The design was chosen because it did work
    | better than anything else on the market. Microdyne was THE goto
    | 'engineer to order' company for reliable telemetry equipment. They
    | didn't dicker on the price. All they asked were two simple questions.
    | 'Can you do THIS'?, and 'When can we have it'. There were constant
    | design improvements as newer components and technologies became
    | available, and as older ones became obsolete. You have absolutely no
    | idea what is involved in designing and building modular equipment that
    | is intended for 24/7 use for decades, with little or no downtime. Some
    | contracts were to take early production, 15 year old equipment and
    | update it to the latest rev. Others were to add new capabilities to
    | existing equipment, to save taxpayer money. In some cases it was pulling
    | the usable modules out of an old chassis and starting over in a new one.
    |
    | Some products were in production for almost 20 years, because they
    | were so reliable. On unit was in constant use for over 30 years by NASA
    | with ZERO maintenance. That was almost 10 years ago, and it may still
    | be working. The cost of that item to the tax payer was down under $2
    | per day.
    |
    | Just because you don't like the design methods does not make the
    | design bad. NASA, NOAA and other government agencies have poured over
    | the designs and suggested no changes. They bought millions of dollars
    | worth of the equipment because THEY liked the conservative designs, and
    | the long life they got for their money. Microdyne was started by two
    | engineers and a salesman who quit Defense Electronics to market a better
    | design. They put their former bosses out of business with that new
    | product. They built a multi-million dollar company around that, and had
    | hundreds of employees.
    |
    |
    | How many people work for you? What equipment have you designed that
    | is in use in space? ZERO? That's what EXACTLY I thought.

    YOU designed this equipment? I think not. Well, maybe one day you might
    have been able to. But you clearly do not understand enough about math to
    accomplish that today. You couldn't even come close on figuring out the
    phase shift over time of 2 very close frequencies (2 Hz apart during the
    time of 1 TV scan line in the NTSC system).
     
  18. Guest

    | wrote:
    |>
    |> YOU designed this equipment? I think not. Well, maybe one day you might
    |> have been able to. But you clearly do not understand enough about math to
    |> accomplish that today. You couldn't even come close on figuring out the
    |> phase shift over time of 2 very close frequencies (2 Hz apart during the
    |> time of 1 TV scan line in the NTSC system).
    |
    |
    | A project that size is designed by a team, or it would never make it
    | to market in time. Of course, no one expects you to know this simple
    | fact of engineering. No one cares about you, or your anal retentive
    | crap.

    I know _you_ don't care. But why is it _you_ need to keep making that
    point?


    | As far as the chroma phase shift, I suppose you know EVERYTHING
    | possible about Quartz crystals? If you did, you would know that they
    | never lock, exactly. The further apart thery are, the more phase noise
    | and chirp occurs. I'll bet you're going to go into great detail about
    | them, but I've seen and used some you'll likely never see, like the 125
    | MHz FUNDAMENTAL CUT crystals we used in some of our tuner modules. They
    | were in gold based TO-5 cans, as well.

    You seem to have some problem understanding locked vs. not locked.

    If it is locked, it will have the same number of cycles as the source
    in the long term. In that case, there is no accumulated phase shift.
    The phase shift may jitter or wobble around. But it will go back the
    other way just as much over that long term.

    If it is NOT locked, then over the long term, there will be fewer or
    more cycles, and the phase shift will accumulate.

    If the local oscillator is NOT locked, your color will be distorted or
    constantly changing. For example, if it gains or loses exactly one
    cycle every field, you'll see the rainbow effect go completely full
    circle from top to bottom of the screen. If it gains or loses that
    one cycle every line (or more radical difference), that color will
    vary full cycle from left to right. If it gains or loses exactly one
    cycle every 10 seconds (rather close, but still not in sync), you'll
    see the color cycle around slowly over those 10 seconds back to the
    same as it was 10 seconds ago.

    You better have it locked, or your color will suck.

    If your crystal oscillator can't lock, then your color will suck.

    If you have an oscillator that shifts in phase by N degrees leading
    then shifts back to N degrees lagging, and back again, over some
    period of time, but never accumulates or loses any cycles over the
    long term, then it *IS* locked. It may be locked poorly, but it is
    locked. The quality can be measured by how far the phase shift goes
    and the modulation of the phase shift.


    | The burst is only availible for seven cycles per horizontal line.
    | The early color burst circuts had to be set up by disabling the burst
    | input, and trimming the oscillator as close as possible to 3.579545
    | MHz. When the burst was turned back on, you had to fine tune it, to
    | center the tint range to the center of the control's range. If this
    | wasn't followed, the color could gothrough a full 360 degree change in
    | one line, as the set drifted.

    That is a case where it loses or gains a full cycle. That is NOT locked,
    at least not to the proper subcarrier. If it happens like this over the
    course of just one line, as you say, then it is locked TO A SIDEBAND of
    the subcarrier, plus or minus the horizontal frequency from it. That
    would be about 3563811 Hz or 3595280 Hz for NTSC. The crystal would have
    to be quite a ways off frequency (at least half the horizontal frequency
    from the subcarrier) to get locked out there. A good RC circuit could
    do better than that. The reason to use a crystal is so that there is
    very little phase noise across the line. Ideally, it will be very close
    in phase when it gets to the next burst, preferrably within a degree or
    two (any more than that and you'd see the phase drift as color shift).
    Then the next burst can pull it back to being in phase, again.

    How many degrees of phase drift do you think is OK?
     
  19. Guest

    | wrote:
    |>
    |> How many degrees of phase drift do you think is OK?
    |
    | You still haven't told us WHICH burst circuit you are using. There
    | are a lot of variables, and no single answer to your vague question.

    I'm not talking about a specific circuit.

    You can talk about any circuit you wish. Just be specific about whether
    it will produce exactly the same number of cycles out to match the source
    it is supposed to be locked to, or if it will produce some finite number
    of additional or fewer cycles over some specified period of time (such as
    a video line time, or video field time), or if it will produce and output
    that cannot be characterized as having some known relationship in number
    of cycles relative to the locking source.
     
  20. Has it ever occurred to you that people may avoid pointing out errors in what
    you say because of your combative debating style, not because they agree with
    what you said? I expect to be attacked just for saying anything that
    disagrees with you, no matter how correct or well-supported what I write is.

    For the record, here is something I wrote (a long time ago) to explain where
    the magic numbers in NTSC come from. The ratio 63/88 does not appear
    anywhere in the original standard that I could see. There are a number of
    other ratios that do appear, and a particular product of them can be reduced
    to 63/88. So that value is theoretically exact - but knowing it doesn't tell
    you anything about where it came from. The note below does.

    Dave

    -----------------------------------------------------------------------------

    This is based mostly on the NTSC committee's own report, with a little bit of
    guessing on my part (in the section about prime factors of divisors).

    Original B&W standard:

    * 60 Hz vertical frequency, so "hum bars" from poor power supply rejection
    are stationary on screen

    * Horizontal frequency is 525*60 Hz. Odd number gives interlaced image, to
    give off better vertical spatial resolution in a fixed bandwidth

    * Channel spacing is 6 MHz, with 4.5 MHz offset between sound and video
    carrier

    * Video is transmitted vestigial sideband, with 4.2 MHz video bandwidth.

    The new color standard needed to be compatible with existing B&W receivers:

    * Colour information would be encoded on subcarrier; subcarrier would be
    visible on B&W receivers in areas of saturated color.

    * To minimize visibility of subcarrier, lock subcarrier to H sync so any
    resulting pattern is stationary, not moving.

    * Use odd multiple of half line frequency, so subcarrier forms a fine
    "checkerboard" instead of lines - less visible.

    * The higher the subcarrier frequency, the less visible on B&W sets, but the
    less bandwidth available for carrying color information. Tests showed the
    best compromise frequency to be around 3.6 MHz.

    * The two constraints above mean that subcarrier should be approximately
    457/2 times horizontal frequency. But 457 is a prime number, and dividing
    by 457 is hard - there are no cheap digital dividers available in 1950.

    * Looking at nearby odd numbers, 453 = 3*151, 455 = 5*7*13, 459 = 3*3*3*17,
    and 461 is prime. 455 is the easiest divisor to generate - all its
    prime factors are 13 or less. So subcarrier is set to Fh * 455/2.

    * So, at this point, the magic numbers are:
    Fv = 60
    Fh = 60 * 525/2 = 15750
    Fsc = Fh * 455/2 = 3583125


    But there's a problem: to minimize visibility of any beat frequency between
    color subcarrier and sound carrier, it is desirable to have the difference
    between the two be an odd multiple of half the line frequency.

    * With numbers above, offset is 916875 Hz. 916875/Fh = 58.21 = 116.4/2.
    So nearest odd multiple of Fh/2 is 117/2.

    * Thus new sound carrier offset should be Fh*(455 + 117)/2 = 4504500 Hz.
    This is (exactly) 1001/1000 times the old sound offset.

    * But (in those days) TV sound used a separate FM transmitter and possibly
    a separate antenna; changing sound offset means retuning the sound
    transmitter.

    * To avoid this, the NTSC moved all the *video* frequencies down by a factor
    of 1000/1001 instead, giving the desired relationship between subcarrier
    and sound carrier.

    * So subcarrier becomes 3583125 * 1000/1001 = 3579545.4545 (rounded to
    3579545 in the original standard).

    * New frequencies (without intermediate rounding)
    Fsc = 3579545.4545
    Fh = Fsc * 2/455 = 15734.266
    Fv = Fh * 2/525 = 59.94

    * The tolerance on these is 3 PPM, so the range of permitted values is
    entirely within the looser tolerances of the old B&W frequencies, so
    B&W TVs should continue to work at the new frequencies (though hum bars
    will now roll slowly).

    * If you happen to have a precise 5 MHz frequency standard, to derive Fsc
    from it your need a multiplier of

    (60 * 525/2 * 455/2 * 1000/1001) / 5000000 = 63/88 (exactly)

    So the numbers 63 and 88 never appear in the NTSC standard; they are just the
    rational number defined by all those *other* numbers above, reduced to
    simplest form.
     
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