PIC
Based WWVB Decoder
By: Steve Hageman
Here is my WWVB
decoder based on a 16C84 PIC. The software is written in CCS 'C'. The
decoder design allows you to connect either an inverted or
non-inverted WWVB signal from any receiver. The design works well
with input levels 200 mV-4V pk-pk. I have used this decoder with my
TRF VLF receiver and my HP-310 connected to a 4 square, east-west
facing loop at my house.
The TRF design has
the WWVB time code non-inverted, while the HP-310 inverts the WWVB
signal.
The output of the
decoder is to an 2 line LCD display that shows the GMT time broadcast
from WWVB. If synchronization is lost with WWVB, the code will
re-synchronize when the signal returns to a usable level.
The program
incorporates a unique noise reduction feature to clean up noisy
signals. At the point where it makes a decision as to whether the
sent code is a '1' or a '0', the program samples the signal 5 times
at 5 mS intervals. If three out of the samples are '1's then it is
assumed that the signal is a '1', else the signal was a zero.
This behavior tries
to clean up slightly noisy signals by 'Averaging' the digital signal
some.
Keywords: Atomic
Clock WWVB Decoder decoding NIST WWVB Receiver
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Modified -
7Jan02