When I first got my SAT, I calibrated my forks to be at exactly 440 when at body temperature. I achieve this by tucking it between by belt and my body for about two minutes. I still have one of those forks in a drawer in my dresser, as a back-up. I check it once in a blue moon. It hasn't changed by a tenth of a cent in eight years, according to my SAT, so I kinda get the impression that the SAT isn't changing either. I was under the impression that the SAT uses a quartz crystal, which can only oscillate at one frequency. Let me know if you think I'm wrong. Kevin E. Ramsey ramsey@extremezone.com ----- Original Message ----- From: "Robert Scott" <rscott@wwnet.net> To: <pianotech@ptg.org> Sent: Friday, January 19, 2001 2:33 PM Subject: Calibration of ETDs > Electronic Tuning Device (ETD) users: > > While looking around for a better way to calibrate TuneLab, I have > revisited the use of NIST services and it seems to me that this can > be a practical means of checking the calibration of not only TuneLab > but SAT and RCT as well. > > The services I refer to are the 500 Hz and 600 Hz standard tones > available on shortwave radio and by telephone at (303)499-7111 (Colorado). > Leaving aside the shortwave option, since most techs do not have access > to shortwave radios, I would like to consider the use of the telephone > service. The number is not toll-free, so it is wise to plan your > use of this service carefully. NIST says this is a very popular number. > They get over 2,000,000 calls per year. When you call this number, > you will hear the WWV broadcast. If you can get your computer or the > SAT to pick up the sound from the telephone receiver, then you can check > calibration. Try holding the telephone right up to the microphone. Before > you call, try to get the dial tone to register on your ETD just to > see if the phone is loud enough. You will want to figure out how to > place the phone on the ETD's microphone so that it will stay put without > your hanging on to it and causing noises that will interfere with > the pickup of the tones. > > In order to be sure of hearing a 500 Hz or 600 Hz tone when you call, > check the following broadcast schedule, which is repeated every hour. > When a tone is present, it is present for the first 45 seconds of the > minute and is silent for the last 15 seconds. As you can see, the > best time to call is between 19 and 24 minutes after the hour, or > between 30 and 39 minutes after the hour. > > Minute Contents > 0 station ID > 1 600 Hz tone > 2 (440 Hz tone) > 3 no tone > 4 no tone > 5 600 Hz tone > 6 500 Hz tone > 7 600 Hz tone > 8 storm warnings > 9 storm warnings > 10 storm warnings > 11 600 Hz tone > 12 500 Hz tone > 13 600 Hz tone > 14 GPS reports > 15 GPS reports > 16 OMEGA reports > 17 600 Hz tone > 18 Geoalerts > 19 600 Hz tone > 20 500 Hz tone > 21 600 Hz tone > 22 500 Hz tone > 23 600 Hz tone > 24 500 Hz tone > 25 600 Hz tone > 26 500 Hz tone > 27 600 Hz tone > 28 500 Hz tone > 29 no tone > 30 500 Hz tone > 31 600 Hz tone > 32 500 Hz tone > 33 600 Hz tone > 34 500 Hz tone > 35 600 Hz tone > 36 500 Hz tone > 37 600 Hz tone > 38 500 Hz tone > 39 600 Hz tone > 40 500 Hz tone > 41 600 Hz tone > 42 500 Hz tone > 43 no tone > 44 no tone > 45 no tone > 46 no tone > 47 no tone > 48 no tone > 49 no tone > 50 no tone > 51 no tone > 52 500 Hz tone > 53 600 Hz tone > 54 500 Hz tone > 55 600 Hz tone > 56 500 Hz tone > 57 600 Hz tone > 58 500 Hz tone > 59 no tone > > In order to use the 500 Hz and 600 Hz tones to check your pitch > calibration, select a no-stretch tuning. If your ETD uses the > fundamental to tune C5 and D5, then customize the stretch for those > two notes so the C5 is stretched -78.69 cents and D5 is stretched > +36.95 cents. Save these customizations in a tuning file or a page > in the SAT memory. These stretches will make C5 exactly 500 Hz and > D5 exactly 600 Hz. If you want to use the standard SAT partials, > then use C3 and D3 instead. The SAT uses the 4th partial to > tune these notes and so you will again get 500 Hz and 600 Hz if you > use the stretch numbers shown above. > > Once you have the ETD all set up to look for 500 Hz and 600 Hz on > C and D, then call the Colorado number at a time when you > can be sure of hearing the desired tones. You will only have three > minutes maximum because they automatically disconnect you after > three minutes. With the tone sounding in the microphone of the ETD, > select either the C or D depending on which tone is playing. Having > the stretch numbers preset in memory makes it easy to switch between > 500 Hz and 600 Hz quickly. Once you determine which tone is playing, > note the rotation of the lights in the SAT or the spinner in the RCT > or the movement of the squares in TuneLab. Any movement in these > displays indicates the error in calibration. If you can adjust the > offset to make the display stand still, then that offset tells you > exactly how far off your ETD is. > > When checking the SAT, you will be limited to one decimal place > in setting the stretch. How much will that affect the results? > Well, if you set D5 (or the 4th partial of D3) to a stretch of > +36.9 instead of +36.95, that difference of .05 cents will mean > that a perfectly calibrated SAT listening to a perfect 600 Hz > ought to indicate sharp by .017 beats per second, which means the > lights in the SAT ought to rotate one light clockwise in 14 seconds. > This is barely recognizeable in the 45 seconds during which you > can observe the 600 Hz tone. And what about the C5 offset by > -78.7 cents instead of -78.69 cents? This error of .01 cents when > listening to 500 Hz means the SAT should indicate sharp by .0029 > beats per second, which means the lights ought to rotate one light > clockwise in 86 seconds - definitely not detectable during the > 45 seconds of 500 Hz tone. > > When checking the RCT, I'm not sure whether you can actually > refine your calibration or just check it with this method, since > Dean supplies a calibrated 440 Hz source to perform the initial > calibration. > > When checking TuneLab you can trim the offset until the phase > display is absolutely stopped and then enter 500 or 600 in the > New Calibration menu. Then you can say that your calibration > is traceable to NIST, the most precise reference that there is. > > And if you do have a shortwave radio, try picking up WWV on > 2.5, 5, 10, 15, or 20 MHz and save yourself the phone call. > However, I have had great difficultly getting a reliable signal > during the day in Michigan. It works better at night. > > -Rober Scott > Ypsilanti, Michigan > >
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