Talk:Time signal

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Cape Town's noon gun is still very definitely in operation. http://www.southafrica-travel.net/westcape/capetown_signalhill.htm Jonathan Warren

GPS for time sync

The article says "The Global Positioning System can also be used as a time reference for radio clocks, but require an accurate 1PPS output to be reliably used for time signals".

Not true. All GPS receivers by definition contain an extremely accurate clock. A few of them produce a 1 PPS output, but that's just an extra feature. There are plenty of GPS receivers that will display the current time when desired, whether they have a 1 PPS output or not.

Paul Koning 14:47, 4 June 2007 (UTC)[reply]

Actually, the first statement is true, as far as it goes. Yes, the GPS satellites all contain atomic frequency standards, and yes, most if not all GPS receivers do display the time. However, firmware which is busy decodng the NMEA sentences, calling up maps, updating the user's position, etc. will output a time that is delayed by up to several seconds with respect to a dedicated time source such as WWV. Additionally, different products have different software/firmware installed, some of which think the on-time mark (OTM) is the beginning of the NMEA sentence, and some of which think it is at the end. A 1PPS signal is essential to the purpose of sending an unambiguous OTM to the radio clock, PC, time server or whatever is being adjusted. —Preceding unsigned comment added by 72.219.144.17 (talk) 00:23, 26 July 2010 (UTC)[reply]

"All GPS receivers by definition contain an extremely accurate clock". GPS receivers by definition do not contain an extremely accurate clock. The whole concept of the system was precisely to avoid receivers having to contain an atomic clock (which would have been required to triangulate a position from three satellites) or any continuously running clock at all. GPS receivers contain an internal clock no more accurate than a regular quartz clock. The receiver initially sets its clock to match the satellite with the least transit delay. It then has to calculate a time to set its clock to, in order to provide the least triangulation difference for each perm of three satellites out of the number being received (but no less than four). A GPS receiver can also calculate a clock setting (and hence find its position) for three satellites only, but only if the altitude of the receiver is known and can be entered on request.

A GPS receiver can find its position on earth even if its clock is initially set to a random time. 86.149.136.154 (talk) 16:38, 26 May 2018 (UTC)[reply]

New York radio time signals

WOR-AM abandoned its use of hourly time signals around 2005, just a few months after its switch to HD radio and after replacing its "classic" signal with a tone similar to that used by WINS. This leaves only WINS and WCBS in that respect. –Wbwn 07:24, 22 June 2007 (UTC)[reply]

PBS as time source?

I notice that some DVD recorders are now indicating "your local PBS station" as a point from which they can automatically set their timers. I presume this is VBI data, at least for the analogue broadcast signal, and note that the article on PBS links to this article among "see also" topics. Nonetheless, this page doesn't mention PBS at all. Is this silence part of a conspiracy by Viewers Like You, that powerful but anonymous organisation that somehow controls PBS and its funding, or just an oversight? :) --carlb (talk) 02:23, 9 June 2008 (UTC)[reply]

radio time signals

When were the first radio time standards? For example the Pulkovo Observatory in USSR started transmitting precise time signals on shortwave in 1920. DonPMitchell (talk) 20:37, 31 May 2010 (UTC)[reply]

WWV (radio station) says that station started time signals and standard frequencies in 1922. CHU (radio station) says that station started in 1929. See Category:Time signal radio stations. --Wtshymanski (talk) 16:25, 4 June 2010 (UTC)[reply]

Electrical time signals

This section is a little confused, and might be taken as suggesting that the first use of electrical time signals was in the US in 1883. That's not true - "railway time" in the UK was an electrical signal and had been around since well before 1850 - and even looking at the US alone, I'm sure it was in use before then. This whole section could do with some research and a re-work to offer a more global perspective. I'll try to come back to it when I have more time. Mortonhall (talk) 14:23, 24 January 2015 (UTC)[reply]