[LAD] A little quiz about audio measurements...

[Gene Heskett]

On Friday 28 May 2010, fons at kokkinizita.net wrote:
>On Fri, May 28, 2010 at 11:24:29PM +0200, Ralf Mardorf wrote:
>> Oberhausen, Rheinland, Germany; power line frequency right now is at
>> 49 Hz, measured with a low cost energy consumption costs meter.
>> Those low cost meters shouldn't be able to do correct measurements
>> ;). The best test at home might be to compare the sound of a
>> transformer with a 50 Hz sine wave.
>
>49 Hz is impossible. It would mean that a clock using this
>frequency would be slow by more than a minute per hour.
>
>Long-term accuracy is extremely high, precisely because clocks
>depend on it. And since almost all of Europe is interconnected,
>adjusting the frequency must be a _very_ slow process. So errors
>of 2 percent really can't be tolerated.
>
>Ciao,
>
I beg to differ a bit.  But this is also OT, sorry.

I can recall an instance while I was C.E.ing at KIVA-tv in Farminfton NM, in 
the later 70's that was certainly odd to say the least.  We had come off the 
network into kiddie hour in the afternoon, with my operator on duty fussing 
because the network ran over, way over, only to discover that no tv made 
could sync to the video coming out of our Sony 2800, 3/4" U-Matic vcr's, and 
moving the tape to another machine made no diff.

Since our power was from the W.A.P.A. grid, which is most of the US west of 
the river, I glanced at the wall clock, which was then still a wall powered 
synch motor clock, and found it was about 13 minutes ahead of my watch, an 
early digital one.

So I called the local power company who had no clue what it was that I was 
talking about, so they gave me another number to call.  Shortening  the 
story here, 3 numbers & 15 minutes later I am talking to the engineer in 
charge in the W.A.P.A. control room (I think in Bonneville Utah), and when I 
said they were running fast, he laughed, so I asked him what time it was, 
and got a quote that matched our wall clock to a second or so.  I said, no, 
its not, its such and such a time right now, and the whole grid is running 
at what my counter says is 71HZ, I had by that time measured it.  So he 
walked over to his vibrating reed meter and of course it was so far off it 
was silent.  He came back to the phone and asked if I could hear anything, 
at which point I could hear the air conditioner blowers almost coasting back 
down to their usual speed, and it was back to about 59.6 HZ, which my vcr's 
with their synch motors and eddy current brakes which made the belts slip 
ever so slightly so that the drum speed was once again 1800 rpms (actually 
1,798.2 rpms, NTSC of course), and we were back on the air.  The wall clock 
was finally right again about 22:00 that night.

The point being that he had the controls that allowed the whole grid west of 
the river (Miss. River) to be dropped about 11 hertz in slightly over a 
minute.  And that is an area larger than Europe I believe.

Pull that today and they would probably send the black helicopters to check 
your bodies DNA.  After the fact.

Yup, broadcast engineering can be a "but that can't happen (but it just 
did)" scenario at least once a week.  I stuck around for 45 years just to 
see what happened next.  And it was quite a ride. ;-)

Now, back to your regularly scheduled puzzles.  Your turn again Fons. ;-)

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
I still miss Windows, but my aim is getting better.