Radio clock WWVB signal generator - Page 1
Forum section: electronics / projects

author: rivest
author_rank: Contributor
timestamp: April 20, 2014, 04:46:47 pm
content: I think Australia suffers from the same problem as several South East Asian countries. There isn't a radio clock tower to transmit time signals reliably to watches and clocks that can receive those signals. For eg, Casio Multiband 5/6, Citizen radio-controlled watches, etc.Would it be feasible to create a home signal generator? We can get the timing source from NTP or even GPS.

author: Rory
author_rank: Frequent Contributor
timestamp: April 20, 2014, 04:49:43 pm
content: Try a web search on "WWVB simulator". WWVB is the callsign of the USA govt. NIST 60KHz time and frequency standards transmitter.

author: Richard Crowley
author_rank: Super Contributor
timestamp: April 20, 2014, 05:43:19 pm
content: It is probably illegal for you to transmit on 60KHz, so you might want to check that before proceeding.You don't really want to be responsible for ships running around or planes falling from the sky, do you?Oddball frequencies like that tend to be used for life-safety things that you don't want to be messing with.If you are going to that much trouble, why not just make a GPS clock and be done with it?

author: Yago
author_rank: Frequent Contributor
timestamp: April 20, 2014, 07:57:31 pm
content: Is the 60KHz a "time slice" rather than transmission frequency?

author: Rory
author_rank: Frequent Contributor
timestamp: April 20, 2014, 07:58:26 pm
content: No, 60 KHz is the carrier frequency.

author: gxti
author_rank: Frequent Contributor
timestamp: April 20, 2014, 10:50:11 pm
content: This was for a repeater, but may be of use:http://ka7oei.blogspot.com/2013/03/getting-atomic-wwvb-clocks-to-work.html

author: NiHaoMike
author_rank: Super Contributor
timestamp: April 20, 2014, 11:39:44 pm
content: A microcontroller PWM output connected to a coil (something like a monitor degauss coil) with a series capacitor and resistor should work well. Use 50% duty cycle for high and something like 2% for low. The power levels involved are so small that interference is unlikely to be a problem. In fact, you'll probably need to have the coil right up to the receiving coils for it to work.

author: GK
author_rank: Super Contributor
timestamp: April 21, 2014, 02:25:30 am
content: It would take a bit of effort to put together a 60kHz transmitter capable of interfering with anything, especially if powered by batteries. 60kHz is a rather long wavelength - about 4600m, just doing the sums off the top of my head. Good luck putting up a dipole for that. I've got four 4CX1000A's in parallel push-pull, and that along with a loading coil the size of a hot water service and a long wire antenna strung the length of my block should get me to that elusive legal limit of 1W effective radiated power on 2200m.

author: vk6zgo
author_rank: Super Contributor
timestamp: April 21, 2014, 04:22:11 am
content: If you only want it to work within your house,it might be workable at very low power.Rather than a proper antenna,you could maybe use an inductive loop,like they use in churches for people with a pickup coil on their hearing aids.A few years ago,I would have said you wouldn't hear anything on 60kHz but the 4th harmonic of thousands of analog TV horizontal output stages!

author: rivest
author_rank: Contributor
timestamp: April 21, 2014, 04:25:22 pm
content: I manage to find someone who is actually working on this.Anyone who is interested can drop me a PM. I don't want to offend anyone with the legality of transmitting 60kHz in our houses.

author: Richard Crowley
author_rank: Super Contributor
timestamp: April 21, 2014, 04:32:21 pm
content: I would like to see continued discussion here. Is anyone here actually "offended" by the concept of broadcasting on 60KHz? (We have become the most easily "offended" generation in history.) Surely it is a bad idea anywhere in North America (interference with WWVB).But using this scheme elsewhere is intriguing and a clever way to use those WWVB clocks in "foreign" terretories. Certainly anyone doing this should do their homework first, and ultimately be prepared to answer to the authorities (in the unlikely event of a "water landing").

author: rivest
author_rank: Contributor
timestamp: April 21, 2014, 04:50:19 pm
content: From what I pulled from my country's spectrum allocation:16 - 150 kHz Unregulated Short-Range DevicesRF Output Power: No valueField strenth: < 66 dBuA/m @ 10mAnd that's the thing, I know many other users in other countries would benefit from this but I'm not sure if 60kHz is regulated for them.

author: David Hess
author_rank: Super Contributor
timestamp: April 21, 2014, 07:31:49 pm
content: People interested in precision time keeping sometimes design and build small transmitters to use in testing their WWVB receiver designs under controlled conditions.They have also been built to support legacy WWVB equipment which fails to operate with the recent upgrades to the WWVB signal.

author: GK
author_rank: Super Contributor
timestamp: April 22, 2014, 12:34:34 am
content: TV horizontal deflection has very high dv/dt during the flyback period, with harmonics extending to MHz frequencies having smaller wavelengths that are much more efficiently radiated. It is these components that are usually the source of interference.At 60 kHz the radiating efficiency of any practical transmitting antenna will be very small. This is true for any antenna, the length of which is tiny in comparison to the wavelength of the frequency radiated. The effective radiated power of any homebrew and entirely in-lab/house 60 kHz transmitter and antenna combination is likely to be so small that no regulatory authority would care less.

author: vk6zgo
author_rank: Super Contributor
timestamp: April 22, 2014, 02:46:43 am
content: Quote from: GK on April 22, 2014, 12:34:34 amIndeed,but even at MHz frequencies,the guts of a TV horizontal output stage are nothing like a resonant length,so "more efficient" may not amount for much.Could it be that we have not had the occasion to listen around 60kHz,whereas we have at higher frequencies?Anyway,it doesn't really matter now,as there are very few analog TVs still in service.Even if some people are still using set top boxes to convert to analog,they'd still be "few & far between".Your second point is why I suggested something similar to the "Audio" loop used in churches,etc with hearing aid pickup loops,rather than a resonant antenna.Actually,the whole idea is a bit silly,as there are plenty of other sources of accurate time.Just put the "radio-controlled" clocks in the back of the cupboard,or sell them on EBay,or something & get on with your life.