In article <2gs9mk$gd6@aurns1.aur.alcatel.com> powers@aur.alcatel.com writes:
>This requires a good ovenized oscillator(that isn't cheap). Rubidium Oscillators
>go for about $20,000 I think. Cesium Beam clocks are > $200,000.
^^^^^^^ ^^^^^^^^^
>The clocks that NIST uses are the best in the world. They have about 10 of them
>that are all averaged together.
>
>WWV, however loses a lot in its method of transmission and to propagation effects.
>Received accuracy (if you have a stable enough PLL to track it without further
>loss of accuracy) is about 1E-7 (0.1ppm) frequency accuracy and 1ms for timing.
>Even to keep this accuracy would cost you at least $1000. Stratum 3 oscillators used in non-central office telephone equipment are 4.7ppm and cost at least $2000.
The Hewlett-Packard Cesium Beam Standard is US$46,000, plus $5,000 for the
clock display and standby battery (sheesh) and $8,500 for the high-performance
cesium beam tube (improves accuracy from +/- 3E-12 to +/- 2E-12, and
improves short-term stability). I know this because, as a sufferer from
compulsive time fetishism, it's on my shopping list for when I win the
lottery. The 20ms accuracy of my Heathkit clock is OK for now, but I'd
much rather KNOW what time it is than have WWV TELL me what time it is.
Their rubidium standard is US$42,000, plus about $10,000 in accessories that
I couldn't live without. Its short-term stability is about 10 times better
than the cesium beam standard (5e-13 over 100s, as opposed to 5e-12 over 1s).
It's just the thing for netting parties, so maybe this could be a club
purchase.
Just for comparison, they also have a quartz frequency standard for $9,500.
Its short-term stability is about two orders of magnitude worse than that
of the cesium beam standard, but of course its accuracy depends on the
standard with which it's calibrated.
The quartz standard also claims very high spectral purity, saying that
spectra less than 1 Hz wide can be obtained when the 5mHz output of the
standard is multiplied to 10 GHz. Perhaps that poor New York repeater
owner with the 243 MHz spur should consider one of these :-).
