240 volts

Yes, most sets use the same IF, but the actual frequency varies depending on how the set was aligned. If you've ever done TV service, you would see this. Since most present day sets use "intermod" sound, at 4.5Mhz, they can get away with this variation. This may be only a KHz or so, but it is real. You can identify the channel by the LO frequency, but you would need a relatively wide band receiver to accommodate the variations.

The fact that the frequencies are so close allows for a receiver with a very low noise bandwidth. The received signals are compared in phase as well as frequency to the "sample" received frequencies for each transmitter. A simple PLL can do this easily with the off-the-air "samples" as reference.

Maybe a Scott-Tee transformer would help! :-) (Actually, one might be used in the rotating antenna servo!) ;-)

| 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".

|> |> 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 :-)

:-)

Mass is the only "constant" that is not defined by a physical entity. It is defined by the standard kilogram, kept in Paris.

This is why 1 cubic centimeter does not equal 1 milliliter, even though NIST tried to legislate it to be, (approximately), true.

A handy reference: (And fun to read!)

It's time for a pfiff!

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...

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)

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!

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.

I lived way out of the city limits a few years ago. The nearest house was a half mile away, and the owner would go to sleep with his TV on. the horizontal sweep drifted all over the place, and would wipe out my WWVB 60 KHz receiver. I had about two volts out of the loop antenna for WWVB, and over 8 volts from his TV, when viewed on my Tektronix scope. To add insult to injury, he was almost in a direct line with the transmitter in Colorado. (less than 5 degrees.)

Au contraire...

A milliliter, derived from liter is a unit of volume. This is a derived unit of measure from the more basic unit of measure length. It is not NIST legislation that defines 1 mL = 1cc, it comes from the very definition of a litre.

There are only a few 'basic units'. Length, time, mass, current, mole, temperature and luminosity. All the others, including many in the metric system are derived from these (e.g. Newtons are derived from length, time and mass)

daestrom

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). So if you have a lot of 'small' numbers to add to a 'big' number, it is best to add all the 'small' numbers together first so that you have a 'medium' number to add to the 'big' number.

Similar problems occur with simple matrix solution methods. Re-arranging the rows such that relatively 'large' values are along the major diagonal minimize the errors. Of course you have to keep track of this so that you can 'un-re-arrange' the solution vector when done :-)

daestrom

The liter was originally defined to be the volume occupied by a kilogram of water, and the gram as the mass of a cubic centimeter of water. This would make the liter equal to exactly one cubic decimeter, that is, to the volume of a cube 0.1 meter (or 10 centimeters) on a side.

Unfortunately, the physical objects constructed to represent the meter and kilogram disagreed slightly. As measured by the standard meter and standard kilogram, the standard liter turned out to be about 1.000 028 cubic decimeters. This discrepancy plagued the metric system for a long time. In 1901 an international congress accepted the discrepancy and formally defined the liter to be exactly 1.000 028 dm.

The liter has since, (1964), been re-defined to be exactly 1.000 000 dm.

And the only one not defined by "natural" constants is mass....

On Fri, 29 Feb 2008 05:13:04 +0000 (UTC) Michael Moroney wrote:

| snipped-for-privacy@ipal.net 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.

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.

Sigh. The reasons are VERY well laid out in older TV design handbooks. Maybe a little reading will open your eyes?

The 5 MHz reference was chosen, because it was generally available at the transmitter site to verify the frequency.

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.

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.

On Sat, 01 Mar 2008 20:11:15 -0500 Michael A. Terrell wrote: | snipped-for-privacy@ipal.net 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".

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.

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.

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.

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.

Why is it people like you, who have NEVER done the work talk down to those who have?

You also said that it was +/- 10 Hz at 14.318180 MHz, when it is +/-

40 Hz

If someone doesn't call you on your bullshit and blunders, then the people who have no clue will think that you are right.

You stated that it would be pulled to whatever the burst frequency was.

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?

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.

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.

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.

A ham radio license and $20 can get you a crappy cup of coffee, and little more.

|>>>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.

On Sat, 01 Mar 2008 23:48:31 -0500 Michael A. Terrell wrote: | snipped-for-privacy@ipal.net wrote: |> |> On Sat, 01 Mar 2008 20:11:15 -0500 Michael A. Terrell wrote: |> | snipped-for-privacy@ipal.net 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.

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.

Once again, sarcasm goes right over your head.

And what? Either ask a question or shut up, troll.

Phil, some people are intuitive, and can see how things work. Others need a pencil to take a crap.

I did. You are the one who claimed it was still +/- 10 Hz at

14.318180 MHz

Did you ever think that they are doing because you are wrong?

Sigh. :(

Right :(

So, you have never looked at what your design is capable of? That is exactly what I expected

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.

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.

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?

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.

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, 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?

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.

On Sun, 2 Mar 2008 19:22:41 +0000 (UTC) Michael Moroney wrote: | snipped-for-privacy@ipal.net writes: | |>On Sun, 2 Mar 2008 04:21:29 +0000 (UTC) Michael Moroney wrote: |>| |>| 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.