Talk:DCF77

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Untitled[edit]

The pseudo-code generates "00001..." (4 zeros), but the text before it says that the sequence is "000001..." (5 zeros).

Correctly observed. I also fell over this. And the specified sequence is correct. The actual (hardware) description of the prbs generator can be found in ref.4(Hetzel). There it can be seen that the lfsr contains an 'all-zero' exception (as is so often done), but also that it is initialized/started to 'all-zero'. I changed the pseudo-code according to this, to have the pseudo-code to correspond with the sequence.

Noudio — Preceding unsigned comment added by Noudio (talkcontribs) 20:00, 20 December 2010 (UTC)

Amplitude Modulation[edit]

The carrier power is reduced to 15% to form the second marks. See "PTB Mitteilungen" Volume 119 (2009) No. 3, "Time and Frequency Dissemination with DCF77: From 1959 to 2009 and Beyond", Bauch, Hetzel and Piester, section 5.2: http://www.ptb.de/cms/fileadmin/internet/fachabteilungen/abteilung_4/4.4_zeit_und_frequenz/pdf/PTBM_50a_DCF77_engl.pdf
Dulciana (talk) 21:28, 14 January 2011 (UTC)

From peter dot martinez at btinternet dot com:
This article refers to the power reduction of 15% power (-8.5dB). There are other references to 25% power, and to figures of 15% and 25% 'amplitude' (without saying if this is power or voltage). Some references include the word 'approximate'. I measure the reduction, on the signal received here, as between 16% and 18% voltage, which is between -15dB and -16dB, or about 3% power. There is evidently some confusion between voltage and power. — Preceding unsigned comment added by 81.158.99.190 (talk) 08:33, 25 October 2011 (UTC)
The article referred above also states that it is definitely the amplitude that is reduced now to its 15%, and that about a decade ago it had been reduced to its 25%, and that before 1970 it used to be reduced to 0%. The reasons for the changes are also given there. — Marosi Gyula (talk) 22:31, 29 October 2012 (UTC)

The figure "Amplitude modulated signal of DCF77 as a function of time" is obsolete: it depicts a signal keyed to a residual amplitude of about 25%. (See note on 15% above.) Also its name ("DCF77_Impulse") is a bit ambiguous because it is not an impulse. — Marosi Gyula (talk) 08:59, 30 October 2012 (UTC)

How sound the signal?[edit]

A sound of the signal in an AM receiver capable of receiving its frequency

Not a good idea; such an audio file would not add any useful information to the article, because the time signal is not encoded as an audible signal. What you hear (if anything) will be highly dependant on the receiver, it's operating mode (AM, SSB or CW) and other settings.
The amplitude modulated signal is a 1 Hz pulse (subsonic, i.e. the frequency is too low to hear it as a tone) with it's duty cycle switching between 10% and 20%. That may sound as soft clicks on some AM receivers. The phase modulated signal will add some noise. A communications receiver in single sideband mode (tuned slightly off 77.5 kHz) could be used to make the carrier audible (and the short intermissions that represent the am time code), but this is not the way the signal is usually decoded.
If you have a java plugin installed in your browser, you may want to experiment yourself with the websdr at http://websdr.ewi.utwente.nl:8901/ (it's a software defined receiver on the internet). Jahoe (talk) 01:50, 29 September 2012 (UTC)
To give you an idea: here's a youtube clip of an SSB (not AM) receiver tuned to DCF77: http://www.youtube.com/watch?v=fURwteHi4Xc Jahoe (talk) 02:00, 29 September 2012 (UTC)

DCF77 Morse[edit]

It seems that the morse code is still transmitted but will be discontinued http://www.ptb.de/cms/en/fachabteilungen/abt4/fb-44/ag-442/dissemination-of-legal-time/dcf77/dcf77-identification-of-stations.html — Preceding unsigned comment added by Braice (talkcontribs) 13:38, 26 May 2012 (UTC)

The information on the abovementioned webpage has already been obsolete. PTB ceased transmitting the call sign in 2006, when they got permission from the German authority to do so. (They actually stopped transmitting the call sign when installed the new signal generator electronics.) — Marosi Gyula (talk) 08:32, 30 October 2012 (UTC)

Swiss violinist[edit]

> For a DCF77 receiver located 1,000 km (621 mi) away from the DCF77 transmitter, due to transit delay the receiver will be set more than 3 milliseconds late.

I think this sentence from the article is incorrect, at least according to the rigorous interpretation of Albert Einstein's General Relativity. The receiver located 100km afar will not be 3 milliseconds late, it will be spot on when the DCF-77 signal arrives, because the speed of light / electromagnetic waves is the universal reference of spacetime. Nothing can go faster than light, thus one cannot prove experimentally that the receiver is late? 62.77.213.125 (talk) 14:45, 23 March 2014 (UTC)