en.wikipedia.org/wiki/DCF77

This sentence overstates what happened in 2003.

PTB’s historical documentation says that in 2003 DCF77 was tested as a possible channel for warning messages. The 2004 PTB news report describes a field test in which 39 test alarms were transmitted between October 13 and December 10, 2003. That is not the same as the bits having been generally “used” for civil-defence emergency signals since 2003.

PTB’s later overview of DCF77 is even more explicit: after describing the 2003 warning-message test, it states that “no decision has been taken so far to actually make use of this possibility” and that the second marks 1–14 were instead used to transmit weather information. So the official record contradicts the claim of continuous civil-defence use since 2003.

In short: 2003 was a trial/feasibility test period, not the start of ongoing operational civil-defence signaling on DCF77.

This sentence incorrectly states that DCF77 uses bits 1–14 to transmit warning messages and weather information as though both services were actually in operation.

PTB’s own description of DCF77 says something narrower:

• warnings to the population could in principle be transmitted using these 14 bits;
• no decision had been made on whether DCF77 would actually be used for that purpose; and
• the same 14 bits were at present used for weather information provided under Meteo Time’s responsibility.

PTB also says, in its longer historical overview, that after the 2003 alerting tests, “no decision has been taken so far to actually make use of this possibility” and that the second marks 1–14 are, instead, used to transmit weather information.

So the article’s wording is wrong because it turns a potential warning capability into an actual warning-message service. The official sources describe weather data as the active use, with warning transmission remaining only a tested/possible use.

This sentence misidentifies where the PZF sequence is applied in the DCF77 signal.

PTB’s official description says DCF77 uses normal amplitude modulation for the 0.1 s / 0.2 s second markers, and in addition uses pseudorandom modulation of the carrier phase. PTB explicitly describes the phase as being keyed according to a binary random sequence, and says receivers that evaluate the carrier phase modulation can achieve higher accuracy.

The NTP project’s own documentation also separates the two families of receivers: DCF77 AM clocks and the DCF77 PZF5xx variants, with the PZF variants treated as a different, higher-accuracy mode. That matches PTB’s explanation that the PZF information is in the phase-modulated part of the signal, not the amplitude-modulated part.

So the problem is not that PZF improves accuracy — it does — but that the article wrongly says the pseudo-random sequence is added to the amplitude modulation. According to the primary source, it is added to the carrier phase.