[time-nuts] WWVB SDR discussion

[rcbuck at atcelectronics.com]

> deriving exact time to way closer than a second from the signal


To the average consumer if the clock is accurate to within a minute or
so they are happy. The clocks also run on a RTC and only use WWVB to
keep the RTC more or less accurate. The clocks are also only looking at
the carrier level change of a signal somewhere around 60 kHz. The newer
BPSK method should be easy to detect in the full power portion of each
second.

I am in Phoenix and the signal should be fairly strong here even during
the day. I know my $15 wrist watch can synchronize during the day if I
take it to a window and point it NE toward Ft Collins. When I visit my
family in north GA the watch always manages to synchronize back there at
3 am each morning.


I bread boarded a RF front end last week end to examine the WWVB signal.
I could not see the signal coming out of my RF front end during daylight
hours. I was using my spectrum analyzer to monitor the output. But by 10
pm the sine wave was clearly visible and fairly strong. I could easily
see the power level drop when it occurred each second.

I have ordered more parts from Mouser (better op amps and FET) to
improve the performance of the front end. I needed more gain since I am
using a modified ferrite rod antenna out of an old AM radio. Hopefully I
will have the new design working by this week end. I am going to build a
clock that uses the BPSK signal. I am not interested in measuring
frequency based on the WWVB signal. I have a GPSDO unit for that.

Ray,
AB7HE

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