On Sat, 11 Jul 2015 04:07:45 -0700 (PDT), Jeroni Paul
wrote:
Nice project. Now I think of someone trying to increase its
range with a power stage and going way too far...
It's amazingly easy to do, but at 60 KHz, the range would be rather
limited. It takes some serious power to produce a field strength
sufficiently strong to overcome atmospheric noise levels.
I guess something similar could be done to generate a DCF77/WWVB signal.
Yep. With a 1 baud data rate, it won't take much horsepower to
generate the code. You can also buy IRIG-H (used by WWVB etc) time
code generators that should work.
https://en.wikipedia.org/wiki/IRIG_timecode
For example:
http://www.gigatest.net/datum/tymmachine_7000.htm
Just add an AM modulated RF signal generator to produce the 60 KHz,
and you're well on your way to becoming the local time lord.
So the algorithm would be: if there was never a sync before or the
user set the time manually = belive whatever time is received,
in this case decoding of several minutes can be done as an extra check).
Otherwise (there was a valid sync before and clock time was not
changed manually) check the received time is within a few minutes of
clock time.
That would help save battery since decoding a single minute would
be enough for safe daily sync.
Well, that would work, but there's an easier way. Since one frame is
exactly 1 minute long, and there's no way to obtain identical data
twice in a row, simply truncating the data to eliminate the minutes
and seconds data, would give the clock an hour to obtain to
identically truncated receptions. No need for a complex sanity check
algorithm. Of course, the receiver would not be turned on for the
full hour, but a successful spot check a few minutes after the first
successful reception would be sufficient to conserve battery power. I
suspect that's the way it's done in the C-Max chips, but I'm not sure.
Diversion: I worked on a failed proposal for an accurate time
distribution system that used carrier current repeaters (i.e.
HomePlug) to distribute the data. The time source was the GOES
satellite system, which belched time sync data on 468.xxx MHz. The
satellite data was to be retransmitted at the home or office over
power line carrier current frequencies (now Home Plug) to any device
that needs accurate time (clocks, computahs, appliances, test
equipment, cell sites, SONET, etc). The difference with other radio
clock systems is that this one would be continuous, not updated
erratically. The GOES signal was strong (+45.5dBm EIRP) that a simple
RHCP patch antenna aimed towards the bird was sufficient. I had it
mostly working when NASA announced that it was going to pull the plug
in 2004. Oh well. Today, it's done with GPSDO driven clocks with
much better accuracy.
GOES time receivers.
http://www.leapsecond.com/pages/goes/
TrueTime 468-DC GOES Time Receiver
http://www.leapsecond.com/museum/468-dc/theory.htm
468-DC SATELLITE CLOCK
http://www.ebay.com/gds/468-DC-SATEL...6640775/g.html
Meteorological Satellite Frequencies
http://mdkenny.customer.netspace.net.au/metsat_frequencies.html#goes-n
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558