Synchronize pocket-size devices

Sure, somewhere you use a "master reference" transmitter that all of them receive and lock to. You do need phase offsets to correct for how far apart they are physically.

In many cases (e.g., GSM cell phone systems) people choose to use GPS as the master reference -- even easier, *and* they can figure out for themselves how far apart they are.

On a sunny day (Mon, 22 Feb 2010 22:27:30 GMT) it happened snipped-for-privacy@cidrek.com (Bill Overton) wrote in :

In the old days TV sync of remote locations was obtained by phase comparing at the studio, and sending a signal via the national FM radio stations, the remote side detected that signal, the signal steered the remote oscillator until phase lock was achieved in the studio (so they could use trick effects). Of course, due to the propagation speed of EM waves, you can only synchronise all oscillators in phase at ONE point. Think about it.

Sync to the AC line from ambient pickup? Or use some available RF, like a TV station? WWV? GPS? How about one of those cheap WWVH watches/clocks?

Do your own RF transmitter/receivers?

Day/Night with photocells? That would be a slow loop.

John

Seems to me you'd need to synchronize each of them to some other standard which is available in all of the locations.

You don't say what the signal generator output frequency is, or how accurate the frequency and phase matching is... and this will heavily influence the sort of standard you need to lock to.

The way this seems to be done at cellphone sites, for example, is to have a local RF oscillator (often 10 MHz) which is disciplined using a timing-grade GPS receiver. The one-pulse-per-second output from the GPS receiver can be used both to discipline the oscillator speed (phase- or frequency-locking) and to give you a top-of-the-second timing pulse. The disciplined RF oscillator drives a frequency synthesizer, and the PPS signal can be used to initialize the phase of the synthesizer.

A similar approach is used by land-mobile radio systems which wish to simulcast a signal on one frequency from several different transmitter sites. Frequency-locking the signals (and perhaps frequency- and phase-locking the CTCSS tone) allows radios in areas of overlapping coverage to receive the simulcast signals without horrible interference between carriers at slightly-different frequencies.

See

The obvious problem is the +/-120 degree phase shift problem depending of which phase you are picking up from the three phase network.

As far as I understand, the US does not have a synchronous AC network. In continental Europe, most countries are in the UCTE synchronous network, however, the ex. CIS IPS, the Scandinavian NORDEL and the UK systems are not synchronous and are floating freely from each other.

In countries, in which there still is an analog service, it would be quite easy to lock into horizontal/vertical synch signal. An analog satellite broadcaster would be interesting (if you find one). Perhaps the best chance would be in the C-band (4 GHz).

WWV in the US, Rugby (60 kHz) or Mayflingen (77.5 kHz) would be a good source in Europe.

GPS would no doubt be the best solution.

If you program the equation of time into your device, you could use a very narrow slit to let the sun rays into the photocell, when the sun passes the meridian. Since the sun is about 0.5' wide, so it takes about 2 minutes to pass a that wide slit, this will significantly reduce the loop time constant required.

until

Wasn't it here in the group? Someone posted a patent where the inventor claimed to have made an RF path or some sort of wunder-antenna where the path is faster than the speed of light, and it sailed past the examiners.

You'd have to put some numbers behind that. Output frequency in kHz or MHz? How many miles is "remote"? How big a battery, battery runtime requirements, etc.?

Wow, I love it! Hmm, but what about cloudy days?

George H.

Many thanks for the replies.

If I just needed to output audio frequencies from the remote devices, I suppose I could use a CB base station or wireless PA to transmit a continuous tone.

That would be an off-the-shelf solution.

For anything higher I could use a frequency multiplier.

How does that sound?

Bill Overton

Phase lock them to MSF Rugby, DCF77 or whatever other broadcast time signal is available in your area. You might have to correct them for geometrical distance from the transmitter depending on the accuracy you require.

Regards, Martin Brown

WWVB is the 60 KHz NIST transmitter.

On a sunny day (Mon, 22 Feb 2010 17:40:27 -0800) it happened Joerg wrote in :

Somebody in sci.physics was selling FTL wire, have not heard from him lately, he claimed NASA ordered some from him. I did try to explain to him how to use an oscilloscope, but alas... Makes you wonder about NASA if it is true :=-) LOL

Navman Jupiter GPS receivers have a 10,oo0 Hz output and a 1 pps output. Trimble has something called a thunderbolt.... Rubidium clocks go for about 70$ used on Ebay..

I'm building this for my ham radio habit:

The old ARRL spread spectrum handbook has a nice circuit using a Vasil Uzunoglu synchronous oscillator and a AM station ....

Steve

What are you trying to accomplish?

You might want to start your research on this site:

ng

lator until

nise

In the really old days, we used to use hundreds of feet of coax tucked up in the ceiling, or underneath the raised floor. Later, that morphed into glass delay lines, which honestly, wasn't much of an improvement. Thank god for software. (Can't believe I'm actually saying that!!) :)