Date: Sat, 1 Feb 2003 09:16:18 +0000 From: barnacle <[EMAIL PROTECTED]> Subject: Re: [LIB] Crystals and time
On Friday 31 Jan 2003 6:34 am, you wrote: > Date: Fri, 31 Jan 2003 06:31:39 +0000 > From: "Matthew Hanson" <[EMAIL PROTECTED]> > Subject: Crystals and time > > From: Rick <[EMAIL PROTECTED]> > > >Temperature changes will affect the oscillation rate of a crystal. Some > >older two way radios had crystal ovens to keep them at a constant > >temperature so the frequency wouldn't drift. I'm sure you'll find that > >the time change varies with the amount of power up time. > > Hmmm... maybe that's why cheap watches that stay right on your warm wrist > maintain time so well. ROFL! You're not going to believe this, but those watch crystals are calibrated for sixteen hours on the wrist, and eight hours on the table. I kid you not! I just built a clock with a 4.096MHz crystal (cos it divides nicely) and that only claims about 50ppm accuracy - about five minutes a year. When I used to care about the broadcast output, we had to maintain calibration of the (PAL) subcarrier oscilator, which is (deep breath) 4,433,618.75Hz. Plus or minus bugger all, officially. We used a counter with a crystal oven that claimed to be accurate to .001Hz. I recall some of the older engineers discussing the fact that the Rubidium master oscillators we used we sensitive even to the slight gravitational changes from the position of the moon at different times of the month. Neil ************************************************************** http://libretto.basiclink.com - Libretto mailing list http://www.silverace.com/libretto/ - Archives -------TO UNSUBSCRIBE------- Reply to any of the list messages. The reply mail should be addressed to: [EMAIL PROTECTED] - Then replace any text on the message's subject line: cmd:unsubscribe --------TO UNSUBSCRIBE DIGEST------ Do above but with this on subject line: cmd:unsubscribe digest **************************************************************
