Re: [time-nuts] Oh dear
On Mon, 2012-05-07 at 18:15 +, Poul-Henning Kamp wrote: We must start out by defining the acceptable level of total distortion, if we choose 0.5% then we need 200 digital levels, roughly 8 of your 16 bits for the signal. That gives you a headroom of 7 bits (leaving one for the sign) and that gives you 42 dB of S/N. Not true in a correctly dithered quantizer (And they almost all are these days)... This is counter intuitive, but adding 1 LSB of uncorrelated noise having the correct statistical properties (Triangular probability distribution) has the effect of completely linearising the conversion process at the cost of adding about 3dB of noise to the system. With the noise added you can hear narrow tones well below the wideband noise floor. In a correctly dithered system the broadband noise floor is the only thing determined by the word length, and narrow band signals can be resolved to well below the noise floor. Further, as the statistical properties of the noise are not all that tightly coupled to its frequency domain properties, it is possible to filter the noise to move most of the energy away from the regions where the ear is most sensitive. 16 bits is actually fine as a distribution format, where is shows up as a little short is as a capture format as at capture time you need headroom to ensure nothing unexpected causes clipping, but once you are done with the processing it is trivial to strip the headroom out and dither down to 16 bits. This discussion would be better over on the Pro audio list rather then time nuts. 73, Dan. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HBG swiss time transmitter shutdown
On Thu, 2011-10-13 at 02:11 +0200, Magnus Danielson wrote: I have wondered if not amateurs could set up small frequency broadcasts of their own. Say a 10 W transmitter or something. It's called a beacon and at least the UK license does allow them (25W maximum) and there are a great many out there (mostly used for propagation studies and the like). Transmitter frequency stability will vary all over the shop, from non ovenised microprocessor grade quartz, all the way up to GPS/Rb disciplined Wenzel sprinter OCXO. I don't know of any carrying time standard transmissions, but that does not mean they do not exist. To be of real use however a time standard transmission needs to be reliably receivable over a wide area, with known accuracy and that is not easy. Having a standard as the carrier generator for a longwave station was ideal as it added little to nothing to the cost of running a very high power transmitter, and made the carrier useful instead of just being a waste of power. Regards, Dan. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS interference and history...
On Thu, 2011-06-09 at 22:30 +0200, Javier Herrero wrote: I don't think it is feasible... for a cooling reason :) You would think the cooling would be a critical issue (It usually is in spacecraft), but the Russians flew a few surveillance birds with reactors on board (and had at least one more such fail to make orbit). Cosmos 954 also failed to eject its core to a safe orbit before reentry and radioactive components were recovered from the impact site in Canada. So yes, a nuclear powered bird is possible, I suspect by running the entire thermodynamic cycle very hot and thereby increasing the radiative cooling efficiency on the 'cold' side. Regards, Dan. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
