[ntp:questions] Re: Why phase modulation

Heiko Gerstung heiko.gerstung at meinberg.de
Mon Jan 9 19:47:08 UTC 2006

Hi, Rob:

Rob van der Putten wrote:
> Hi there
> Why does DCF77's phase modulation (DCFp) offer a more reliable timing then
> AM?

 From our DCF77 info page (http://www.meinberg.de/english/info/dcf77.htm):
"In order to increase the accuracy of the demodulated time marks, the 
carrier of DCF77 is additionally modulated with a pseudo-random phase 
noise. The pseudo-random sequence has a length of 512 bits which are 
transmitted in the time interval between the AM marks. Due to the 
pseudo-random characteristics of the sequence, the mean deviation of the 
carrier phase is still zero. The phase modulated carrier can be received 
with a larger bandwidth. Correlation algorithms known from satellite 
techniques let PZF receivers determine the correct time with an accuracy 
of some microseconds which is much superior to the accuracy achieved by 
standard AM receivers."

> Who produces these recievers and what do they cost?
> Is GPS better or cheaper then DCFp?

AFAIK we (Meinberg) are the only vendors offering such a technology. See 
for example:

NTP Time Server with PZF receiver: 

Radio Clock Module

(this one can be ordered as a standalone rack-mountable system with 
power supply and housing)

and any other products with a "PZF" in their name :-)

> Regards,
> Rob

Kind regards,

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