Wolf,
Does the Rockwell Jupiter TU30 GPS module (used by DF6NM, OE3GHB and me
and others) provide this NMEA informations too? And how will we feed the
informations to SpecLab? You mentioned the soundcard, but how is this
possible? We would at least need a stereo soundcard, right?
73, Stefan
Am 10.04.2011 13:39, schrieb wolf_dl4yhf:
Hello Stefan,
Yes, the charm of the GPS-sync'd sampling is that it allows truly
coherent transmission - even after the program was shortly stopped, PC
rebooted, generator re-fuelled, or whatever strange things may happen.
The sine wave generator will (optionally) not calculate the argument
based on the number of soundcard samples, but derived from the
GPS-derived time of day. Which, with the GPS 18x LVC mentioned before,
seems to have a resolution (not neccessarily a precision) in the
sub-microsecond range (192 kHz SR -> 5.x microsecond samples, but
internally interpolated to a higher sample rate near the slope of the
sync pulse).
At 192 kHz sampling rate, I get a standard deviation in the measured
pulse position of only 30 to 60 nanoseconds (per one-second-interval)
measured over one minute, which almost sounds too good to be true.
Thus i'm a bit sceptic, this needs more testing.
Some preliminary info about the GPS-based calibration is already
available here:
http://www.qsl.net/dl4yhf/speclab/frqcalib.htm#gps_pps_output
Note: The NMEA decoder for the soundcard is not implemented in the SL
version on my website. It will be implemented when the weather(!)
permits ;-)
73, Wolf DL4YHF
(off for a walk now..)
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