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DCF77RX(1)		    General Commands Manual		    DCF77RX(1)

       dcf77rx - soundcard DCF77 (and HBG) beacon receiver

       dcf77rx	[-a  audio  device]  [-s] [-n] [-v verboselevel	(1 or 2)] [-g]
       [-p] [-l] [-u] [-t]

       dcf77rx is a soundcard demodulator for time reference signals transmit-
       ted  by	the  transmitters DCF77	and HBG	on LF frequencies. The program
       expects the transmitter signal downconverted to	an audio passband fre-
       quency  of  1kHz	by an LSB or USB receiver.  A circuit for home-brewing
       such a transverter is included in the docs of the hf package.

       The decoded time	information is used to derive correction  factors  for
       the sampling rate, the gettimeofday clock  and to measure the exact CPU
       clock frequency.	 These clock sources are used for  calibration	in  my
       AMTOR/Pactor1  package  (hf)  as	reference clocks. This program is part
       of the package.

       -a     specify the path to  the	sound  driver  (default:  /dev/dsp  on
	      Linux, /dev/audio	on Solaris).

       -s     use  standard input instead of audio input. Format is 8kHz 16bit
	      words 1 channel in the endianness	of the CPU.

       -n     do not use the `mmap()` way of approaching the soundcard,	 which
	      means,  do not read directly from	the soundcard dma buffer. Some
	      soundcards do not	support	mmap mode. This	option	is  experimen-
	      tal, it is not yet tested	how good the results will be!

       -v     Set the verbosity	level (1 or 2, default 0). The higher the num-
	      ber, the more debugging information is written  to standard  er-
	      ror.  At	first  use,  try  level	 2 to get familiar with	how it

       -g     HBG mode.

       -p     DCF77 phase mode.	DCF77 transmits	the time information amplitude
	      modulated	 and  phase  modulated with a pseudorandom code.  This
	      option uses the latter to	decode the  time.   This  is  strongly
	      recommended,  as the PN code is more robust and allows much more
	      exact determination of the second	pulses.

       -l     Receiver uses LSB	(lower sideband) mode.

       -u     Receiver uses USB	(upper sideband) mode.

       -t     Set the system time to the received MEZ btw MESZ (CET btw	 CEST)
	      from DCF77.

       In  DCF77 BPSK PN mode, due to the small	number of searchers and	there-
       fore low	system load, the receiver requires around 15sec	to acquire the
       second clock.

       Due to the nature of the	amplitude modulated transmissions from HBG and
       DCF77, the receiver is quite sensitive to noise and preturbances.

       The receiver requires more than one minute to acquire time, due to  the
       nature of the transmissions.  To	calculate correction factors, the pro-
       gram should run at least	15  minutes.   Tune  the  receiver  patiently,
       first  so  that the carrier frequency offset is smaller than about 1 Hz
       (you see	it with	-v 2) and then the second ticks	should be  catched  as
       secondly	 as  possible, you can see this	by the rotating	rod or also as
       text with -v 2.	Best calibration time is daytime.  Do not believe  the
       first  output,  see  if an exact	value comes repeatedly,	because	errors
       are possible due	to noise!

       Hans-Guenter DF4OX/DL0PTB sent me printed documentation about the DCF77
       transmission format which helped	me a lot.

       Thomas  Sailer, HB9JNX/AE4WA, and some small adds
       by Gunther Montag,

HB9JNX				DCF77 utilities			    DCF77RX(1)


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