On Tue, 22 May 2012 15:49:04 +0000 (UTC), "Geoffrey S. Mendelson"
wrote:

Jeff Liebermann wrote:

Many switching power supplies run at about 60KHz. I have one
somewhere around my computer/TV pile, which kills WWVB reception if I
get anywhere near it.

Exactly, how many people have one?

My guess(tm) is that it's the power supply in my DirecTV DVR. There
are plenty of those out there.

Most WWVB devices have an indicator on the LCD display to show that
the clock was recently synced with WWVB time. My weather stations and
assorted digital clocks all have this feature.

What's recent? 1 minute? 1 Hour? 1 Day? a Week?

The manual for the wx station says within 24 hrs. That makes sense as
60KHz skywave doesn't work too well until after about midnight. I
suspect it's lucky to get one update per day. That should be
sufficient to deal with any clock drift. When I was stupidly running
it next to my computer/TV pile, it would never update. I vaguely
recall that it drifted fast at about 5 minutes per month. Now that it
gets updates, it's dead on. See:
http://tf.nist.gov/general/pdf/1976.pdf
Section 4, for recommended synchronization practices.

It's my understanding that only the modulation scheme will change, not
the encoded data. A universal chip that works using both system
should be possible without a major price jump.

Well no. The data is the same, but a new receiver needs to be used.
The old one just did on/off for an AM pulse, the new one uses BPSK,
which is two tone modulation. So not only does it have to decode
the carrier being there at all, it has to decode two different tones.

Nope. It's not two tone. It's a phase shift of the AM carrier,
switching from 0 degrees to 180 degrees for 0/1. See video at:
http://www.youtube.com/watch?v=mOjwxq5flTg
I had thought that they were going to broadcast each separately, but
apparently it's simply adding PSK to the existing AM carrier. Clever,
methinks.

Then you have to decode the BPSK stream to get the data.

Yes, you have to modify the chip. However, it's really easy to build
a BPSK to OOK (on off keying) converter, so an adapter is possible.

This not a big
deal, you could do it with a sound card and a microprocessor, but it's
a different receiver design, and reprograming the microprocessor.

While it's possible to demodulate a 60KHz carrier with a sound card,
it would require a high end 192KHz card, and not a generic card that
maxes out at 44KHz.

The kind of thing that if you really were going to sell 50 million of them
you could do it for a few dollars a chipset/board, which is probably what the
current ones cost, but if you want to break even with 10,000 you have to
sell them for at least $100, maybe more.

Well, keep your eye on C-Max. When they produce a suitable BPSK chip,
that should set the price point. It's this type of potentially high
volume market that really attracts the chip vendors.

It's like I saw an article about an Israeli startup that had sold 200,000 of
their product. The article was entitled "sales of xxx disappointing".
I guess they planned on selling a million of them. :-(

Kinda like the Windoze Phone 7?
http://www.dailytech.com/Ballmer+Admits+Windows+Phone+7+Sales+Are+Disappoin ting/article22747.htm
It was really clever of MS to prematurely announce the WP8, and then
leak that there's no upgrade path from the WP7 to the WP8.

I'm a bit mystified with the "new type of PM receiving antenna"
mentioned in:
http://www.nist.gov/pml/newsletter/radio.cfm
I didn't know that antennas were modulation specific.

Where have you been the last five years? I surprised that you have not
been swamped with HDTV antennas. :-)

Sigh. I assumed that it was too early for the marketing hype in the
"atomic clock" market. My apologies for being so naive.

Incidentally, I designed stick-on metallic label, that you attach to
your ordinary TV antenna, that turns it into an HDTV antenna.

I expect it's another gimick to say you need to buy a higher gain antenna,
or that's why your device can't sync. I expect that everyone will need
to buy 1/2 wavelength end fed wires.

(for the humor impared, that's a joke, a wavelength is 5 kilometers).

Sorry, but zoning ordinances do not allow covering the neighborhood
with giant antennas. The authorities claim that it attracts
lightning, cosmic rays, and aliens from outer space.

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