Re: WTF with my computer clock?

On Tue, 18 Aug 2009 07:59:05 +0000 (UTC), "Geoffrey S. Mendelson"
<gsm@xxxxxxxxxxxxx> wrote:

Jeff Liebermann wrote:
I don't know that much about the code used by WWVB. (I are not a
programmist).

It's a very simple system that is well documented. It's simple and slow
enough that anyone used to pulling apart data streams would be able to
decode it with a Z80 derived embedded processor, the ARM chips in dead iPods,
WiFi routers, etc would be "overkill".

Perhaps simple, not for me. I'm a lousy programmer and avoid
programming as much as possible. However, taking a closer look, it
does look rather simple.

Here in Jerusalem, we don't receive the signals of WWVB, or the German
or UK equivalents here. Someone about 50 miles north and out of the
mountains has a clock that syncs, but he never told me which station it
uses (he may not know), or how often it syncs.

See:
<http://en.wikipedia.org/wiki/Radio_clock>
There's a list of other LF time xmissions. I wouldn't give up trying
to hear various LF broadcasts. The problem is that they work best
late at night. From Israel, I would not expect to hear them with an
extremely short antenna. You may need to build a real LF antenna,
with proper matching circuit, and possibly a FET RF amplifier. Maybe
start with a loop antenna, which might be easier and grow as needed:
<http://www.febo.com/time-freq/wwvb/antenna/index.html>
<http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=350226240076>
<http://www.geocities.jp/bitalemon3000/english.html>

More on the C-Max receiver kit:
<http://www.prc68.com/I/Loop.shtml>

This lead me to research
how one would do the opposite, devise a local transmitter with an
ethernet port on one end for NTP sync and a 60kHz transmitter to sync a
clock on the other.

Building a store and forward repeater for WWVB (or the EU equivalent)
60Khz is a waste of time. The storage delay needed to regenerate the
signal will result in the sync pulses arriving too late. However, a
system that uses GPS, GLONASS, or Galileo as a reference, and
generates a simulated time code format will work. The problem is that
at 60Khz, the necessary antenna farm would be huge and the
transmitters rather power hungry. WWVB runs at an EIRP of about 70kW.

I gave up due to lack of a suitable design for the transmitter, no receiver
and a lack of funds to obtain them. You probably could do it out of one
of the Linux based routers, and blink one of the status LED's to generate
the 50/60kHz signal.

Starting with NTP, GPS, or a Cesium or Rubidium clock will work.
However, I don't know about the effectiveness of cramming it into the
limited abilities of a commodity router. Methinks you would be better
off with a SBC (single board computer) or common PC (ITX, Mini-ITX,
etc).

Actually, a 60KHz xmitter is fairly easy to design. The problem is
that all the components would be huge. There's also the not so easy
problem of getting Ministry of Communications approval. It's not on
the designated ham radio frequency list:
<http://www.moc.gov.il/sip_storage/FILES/0/390.pdf>
I'm sure that nearby users that went through the trouble of obtaining
large antennas, will not be thrilled with your transmissions. Even a
"local" transmitter can carry a substantial distance at 60KHz.

I know by now you must be thinking "why would anyone even think of such
a thing", but a discussion a few months ago about resurecting a Heathkit
Most Accurate Clock, got me going. I think I also read a posting that the
WWVB signals were being phased out.

The GC-1000 used WWV at 5,10, and 15 MHz, all of which are still on
the air. I'm not sure what a 60KHz system would do for you.

Repair your Heath kit GC-1000 Most Accurate Clock
<http://www.amug.org/~jthomas/gc1000.html>

I've given up asking "why". Some of the strange things I've seen on
the internet defy logic and explanation.



--
Jeff Liebermann jeffl@xxxxxxxxxx
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
.

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