Simple 60 Khz Transmitter Design?

I would love it if, once you've successfully figured this out, you would post blueprints to the design. I am curious how you are going to send a correct time code. I found this website

which details the necessary binary to code for the time. I hope that helped and I look forward to seeing your finished product.

P.s Stop bashing the idea as unnecessary. This seems to me to be an intellectual pursuit which has spouted from a minor dilemma. If I understand Sean at all, he is interested more in seeing if he is capable of solving a problem than if the product has significant practical value.

Probably the latter - given the nature of the time code transmission, most things looking for it are going to look for the pattern of it, so a carrier that does nothing would be treated as irrelevant. Speculation, but...there's a lot of noise in that region, per multiple articles on the subject.

You have hopefully armed yourself with a copy (free PDF download) of NIST 960-14? it should give a good idea of what you're trying to accomplish, and some insight on how the watch might be trying to do it.

At the risk of offending those who want everything to be perfect: if you hang some wire off the end of your scope probe and poke it into the middle of the transmitting coil (or near whatever you are using as an antenna), do you get any pickup?

--
Cats, coffee, chocolate...vices to live by

Okay, I see that this thread still needs an answer. I did almost exactly what you were asking for. I use to travel to Europe a lot and I ended up with a DCF77 radio controlled clock. Not enough signal here in Seattle to set the clock, so I build a circuit to set the clock from a DCF77 simulator.

You can see the schematic at:

This particular clock only demodulated the time code and wouldn't show that it was receiving anything until I had the code AND the carrier right.

I hope this meets your requirements.

Some notes:

The clock is pretty sensitive to overload, so the antenna has to be several feet away. Also, watch out for computer monitor overloads of the signal. You can use just about any rod as long as you can get to your resonant point. I built this into a small plastic box using a piece of copper clad as the board to hold the parts. Digi-Key and Mouser have 60kHz crystals.

The input on J1 is a simulated time code at TTL/CMOS levels. I used the CD4069UB as it will run from just about any voltage from 3 to 15. Q1 is not needed if your whole system is at 5 volts. My clock checks at the top of each hour for time code. The drift is only a few seconds per month, so the battery last "forever." (4-AA are even better).

I keep my DCF clock on time with this (time code comes from a GPS receiver).

Have a look at the WWVB specs to get the modulation right for your watch.

Have fun and good luck. Is this what the thread was looking for?

Steve Swift

--
Steven D. Swift, novatech@eskimo.com, http://www.novatech-instr.com
NOVATECH INSTRUMENTS, INC.      P.O. Box 55997
206.301.8986, fax 206.363.4367  Seattle, Washington 98155 USA

A chip design AND the codes can be seen at...

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
         America: Land of the Free, Because of the Brave

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Wow, thats more like it! Can I ask for a little more guidance with C4 and L1? What sort of value should I be trying with C4? I imagine with L1 you are saying you are wrapping 100 turns of wire around a former of some type? Are the turns all side-by-side? What kind of rod are you sliding into it?

I'll just order the lot from Digi-Key if I can, seems like a much more elegant starting point than my work thus far. At least I know someone already has this system successfully working. I may even just stick to the DCF77 format if I can find enough information on it, as my watch will pick up either.

I have tried a quick encoding of my signal, but no luck so far. The watch still says it is not receiving data. I have written a small app that creates the necessary code, then passes it off to a small square on the monitor (flashing it white or black). This looks by my eye to be plenty accurate enough for the 1 bit per second rate, but if it ends up being too sloppy I'll have to come up with a more precise method. The 555 does seem to suffer a small amount of drift though, and if it really does need the frequency to be within a couple of Hz I probably have no chance with it. To be honest I'm not sure how I'll perfectly adjust this circuit either, as I can only see down to 0.1 KHz with my meter...

Sean

meter...

Poxy hell. Just how dense are you. All you were given was a crystal controlled oscillator, like we told you to use, and a modulator. NOT the circuitry to generate the modulation pattern, which we have also discussed. We are NOT saying you cannot do this, we have been trying to explain that it actually is a complex piece of equipment that you are trying to build. Quit being so dismissive of the very good advice that you have received here.