[time-nuts] wwvb d-psk-r predictive approach success

[paul swed]

Hello fellow time nuts. I started a long journey to deal with the wwvb BPSK
signal over 3 years ago. Since then I have released reactive solutions that
have been shared. Generally in the form of costas loops for phase tracking
receivers like the Fluke 207 etc and then the remodulator for the
timeclocks like the spectracoms and true times. But there has always been
other possible approaches. I sent an email over a year ago called the
cheat-n way. Several of you had also suggested GPS assisted or predictive
methods. Never lost but a suggestion doesn't get you to the end game.

That said I finally went down the path as many things came together.
Learning C, Arduino, getting the NIST document etc and in reality a week
and a half ago I really wrote the program that seriously works well.

Essentially it works as follows.
Predict WWVBs time code in advance using the GPS sentance. Then march the 1
second bits out exactly 107ms after the wwv/wwvb Tick and use the GPS tick
to keep things in step.
Phase change on the BPSK signal occurs at 100ms and the east coast is about
7.5ms from wwvb.
The time code simply flips a invert non invert switch in the form of a
simple home brew double balanced mixer. Not to many 60 Khz DBMs around. By
the way the transformers are the ethernet filters mentioned here a year ago
by another time-nut.

I started testing this a week ago and its been reliable. Its great to
listen to wwvb again on the fluke 207 thats stable and locked. To watch the
charts over days with the diurnal shift and such. All like the gud ole
days. It works with the HP 117s and as a added bonus all of the old clock
systems I have work. Thats the spectracoms and truetimes netclocks etc.

So how complicated is the solution as compared to others I have released
its simple.
NEO 6 GPS receiver, 2 simple logic chips 14 pin dip class, an Arduino UNO
or Nano or Mini.
All total $25 maybe? Nice big stuff you can use a soldering iron on. The
modulator slips between the old preamp and old receiver. It passes the DC
around to the preamp.

I will release all details schematics code as always. Sorry no kits will be
made.

Additional notes.
Not a bad first project for C and arduinos. Use 30% of the space so its
kind of big.
But the code is very linear and should be very clear. I also built in
tables for 10 years worth of operations Leap years and such. A table that
washes out any error in a given year. Always starts coding correctly on the
nearest minute.
I will say there are 5 to 10 bits in the sequence that simply depend and I
have them coded but there isn't a good way to know what they should be.
There is a 5 bit sequence called ls_DST in the nist standard and though I
read the details its not clear how to code them in relation to some date or
something for 10 years of predictions. Doesn't seem to matter because what
I see is a single or so bit error doesn't upset the old receivers. Still
curious minds would like to know.

Regards
Paul
WB8TSL