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Radio time signals throughout the world Wouldn’t it be great if all your watches and clocks would adjust themselves automatically to the current time and also adjust themselves for daylight saving? There is a simple way to do this in many countries – and possibly even in Australia. It doesn’t require internet access or even a GPS receiver! M any people today use a phone, or a smartwatch linked to their phone, to tell the time. The time on most phones is very accurate, being derived from atomic clocks and associated time servers which is then broadcast over the mobile network. But some people still use a conventional watch or a clock to tell the time. Most digital watches are very accurate, only gaining or losing around 15-30 seconds per month, but they still have to be set manually. That is difficult to do precisely. Some clocks connect to WiFi networks and are synchronised to atomic clocks via time servers, and we have published several such designs in the past. Others synchronise to GNSS satellites such as GPS, which carry atomic clocks; again, we have published quite a few projects which do that. siliconchip.com.au But some watches and clocks synchronise their time with atomic clocks via radio signals, and that is the subject of this article. Timekeeping devices can receive radio signals through several methods. One is dedicated LF (low-frequency, 30-300kHz) signals from dedicated transmitters, which are operated in Europe, the United States, Japan and China. Another method is by dedicated signals transmitted on the shortwave band, with transmitters broadcasting on a variety of frequencies from 2.5MHz to 25MHz. These dedicated LF and SW time signals contain the time, date, leap second and other information encoded in digital form. Some stations such as DFC77 also by Dr David Maddison encode weather or other information. Many of these time signals can also be used as basic frequency standards. You can hear audio samples of a variety of LF and SW time signals at www.sigidwiki.com/wiki/ Category:Time Many normal AM (medium-wave) broadcast band stations also broadcast hourly “pips” at 1kHz, usually on the hour. These pips were first introduced by the BBC in 1924, and they were originally synchronised to Greenwich Mean Time (which varies slightly due to wobbles in the Earth) but since 1971 have been synchronised to International Atomic Time (which is more consistent). For those interested in those signals, there is additional information at www.miketodd.net/other/gts.htm No commercial receivers appear to take advantage of these pips, which Australia’s electronics magazine February 2021  9 Fig.1: demodulated audio of the BBC’s 1kHz Greenwich Time Signal “pips”, as heard on the hour since 1924. When there is a leap second, an extra pip is added. This was also used extensively in Australia but has now largely been replaced by the familiar six 500ms-long, 735Hz pips marking the start of the new hour. Image credit: Mtcv. are hour markers only and provide no further information. But they can be useful to visually determine that a clock is set accurately on the hour, if not necessarily to the correct time. In Australia, most AM stations (in particular) broadcast a series of six 735Hz pips in the five seconds before the hour, with the leading edge of the last pip marking the exact new hour. Most stations have radio silence during this period, although some use the otherwise “dead air” to play station ID or intro to news services over the top. Other methods of receiving time signals over the airwaves include: • digital television signals; both DVB (as used in Australia) and ATSC standards support time and date transmission to a receiver for program scheduling • commercial FM radio via the Radio Data System (RDS), which can be used to set attached clocks such as a car clock and time; timezone and date information is also sent • Digital Audio Broadcasting (DAB) which carries a timestamp in BCD (binary coded decimal) format • Digital Radio Mondiale (DRM), which can be decoded with a software-defined radio (SDR); see the S ILICON C HIP DRM article www. siliconchip.com.au/Article/10798 LF radio time signals Even today, with widespread internet access and low-cost GPS receivers, time signals over radio can be useful. LF (low frequency) radio time signals have very wide coverage (but not global, unfortunately) and the technology is relatively simple and cheap to implement. It is a lot simpler to have a wall clock, watch or other time-dependent device synchronise by LF radio signals compared to using a GNSS receiver or WiFi or phone connection. Also, the nature of LF radio propagation is that one transmitter with a relatively low power output can give excellent coverage, as the radio waves are propagated by either a ground wave or between the ground and the ionosphere (which acts as a waveguide) with a wavelength of kilometres. Edge diffraction helps the signals go around mountains and other obstacles, and building penetration is good. The wavelengths of LF time signals in use for consumer timekeeping are 1851-7500m. LF radio frequencies are used because their propagation characteristics are predictable and propagation delays are less than with shortwave, although shortwave time signals are also used. There are several different low-frequency time transmitters around the world. These are: • DCF77 in Mainflingen, Germany at Fig.2: locations and nominal (reliable) coverage areas for LF radio time signal transmitters. People report being able to receive JJY (Japan) at certain times in some parts of Australia and NZ. 10 Silicon Chip Australia’s electronics magazine siliconchip.com.au 77.5kHz (50kW with 30-35kW effective radiated power [ERP]) • MSF in Cumbria, UK at 60kHz (60kW with 17kW ERP) • JJY in Fukushima, Japan at 40kHz (50kW with 13kW ERP) and Kyushu Island at 60kHz (50kW with 23kW ERP) • WWVB in Colorado, USA at 60kHz (70kW) • BPC in Henan, China at 68.5kHz (90kW), although the signal is proprietary • RTZ in Irkutsk, Russia at 50kHz (10kW) • ALS162 (formerly TDF) in Allouis, France at 162kHz (800kW) These signals cover mostly Europe, the United States, Japan and China (see Fig.2). There is no official coverage for Australia or New Zealand, although it is possible to receive some of these signals in Australia under certain conditions, which we will describe later. While other services provide radio timekeeping on shortwave frequencies, most radio-controlled consumer clocks and watches use LF signals. The nearest radio time signals accessible in Australia under appropriate conditions are JJY Japan (LF), the proprietary BPC signal from China (LF) and also WWVH (SW) from Hawaii, USA. JJY is about 7773km from Sydney while WWVH is around 8200km and WWVB (LF) in Colorado is about 13,000km away. Note that many radio-controlled watches or clocks are called “atomic”. Seconds markers normally 50ms of 1000Hz but markers 55-58 are 5ms of 1000Hz and seconds marker 59 is omitted. Minute marker is 500ms of 1000Hz. During the 5th, 10th, 15th (etc) minute, seconds markers 50-58 are 5ms of 1000Hz Time code transmission (UTC) - valid at next minute. Binary ‘0’ duration is 100ms, Binary ‘1’ duration is 200ms. Parity check bits P1, P2 and P3: counting the binary ‘ones’ of each group plus the corresponding parity bit gives and even number. Normal seconds markers of 1000Hz, emphasised by 50ms of 900Hz. Tone immediately follows. Seconds marker 20 has a duration of 200ms. Designates the start of the time information. Fig.3: the now-extinct Australian Radio VNG time code format. VNG was considered unnecessary by the government and closed in 2002. This is not the correct terminology; it relates to the fact that the radio or GPS signals they receive are derived from atomic clocks. There is no atomic clock in the device itself. Apart from domestic watches and clocks, LF time signals, where available, are used by many industrial timekeeping devices. This includes radio stations, railways, energy supply companies, road control equipment such as traffic lights (which have to change to different schedules depending on the time of day), and just about anything that needs an accurate, reliable time within the range of a transmitter. Former Australian SW radio time signals Australia once also had its own shortwave (HF or SW, not LF) time signal station – radio VNG, Lyndhurst, Victoria. It was shut down in 1987 and relocated to Shanes Park, (Western Sydney) in NSW. This was again shut down in 2002. The closure inconvenienced many scientific users at the time. See Fig.3 and the video titled “A visit to VNG Lyndhurst 1986” at https://youtu. be/61C6IyWEqZE Apparently, the government thought that GPS timekeeping signals would take over. But in Europe, Japan and The Author has personally received a valid signal on his radio-controlled Citizen watch while camped on the side of Mt Bogong, Vic. Source: Casio. siliconchip.com.au Australia’s electronics magazine February 2021  11 Fig.4: legacy amplitude modulation WWVB time code format. Source: Wikimedia user Denelson83. the USA this is not the case, and there is still a huge and increasing demand for radio timekeeping services, especially on LF. Purely for interest’s sake, you may wish to look at plans published in Electronics Australia, July 1995 to use the 5MHz signal from VNG as a very accurate frequency reference. There is also a partial description of building a receiver and decoder for VNG time signals at www.electronicstutorials.com/receivers/vng-receiver. htm was used to synchronise power plants and phone networks. It is operated by the US National Institute of Standard and Technology (NIST). The location was chosen because of high soil conductivity, which provides good antenna performance. It broadcasts to an estimated 50 million radio-controlled watches, clocks and other devices in the USA. Original experiments with 60kHz transmission began in 1956, with station KK2XEI having a radiated power Fig.5: the antenna complex for WWVB at Fort Collins, Colorado, USA. of 1.4W. It proved that the 5km-wavelength signals could be propagated in the natural waveguide between the ground and the ionosphere, with 100 times more stability compared to shortwave transmissions. These signals could also travel great distances with a low transmitter power; the 1.4W signal could be received in Boston, 3137km away. A 4kW transmitter was then set up for more serious use, and it was increased incrementally to 50kW in 1999 and then again to 70kW in 2005. In 2012, an additional time code format called phase modulation was introduced, which improved decoding capability while maintaining backward compatibility with legacy devices. The extra power, along with the new modulation scheme, enabled many new and tiny devices to take advantage of the signal. It was anticipated that devices such as refrigerators, ovens, cars, traffic lights, irrigation systems etc would take advantage of the new encoding system. Legacy systems (with rare exceptions) are insensitive to the new phase modulation information transmitted, so continue to work. With phase modulation, a code independent of the legacy amplitude There is a trio of interesting, related projects at www.qsl.net/zl1bpu/ MICRO/VNGBOX/ One of these is a timecode generator for timestamping events using the VNG time code format, although the time signal is derived from GPS signals, since VNG no longer exists. We will now look at some of the radio time transmitters around the world. WWVB in the USA WWVB is the 60kHz LF station at Fort Collins, USA. It has been broadcasting since 5th July 1963, although it did not broadcast a time signal until two years later. At the time, the signal 12 Silicon Chip Fig.6: a diagram of the WWVB antenna arrangement, showing the capacitance hat structure (topload) of each antenna. Source: NIST. Australia’s electronics magazine siliconchip.com.au Fig.7: the time code format for WWVH (shortwave) from Hawaii, USA. This can be picked up in Australia under the right conditions. modulation scheme is transmitted via binary phase-shift keying of the carrier wave. A ‘one’ is transmitted by inverting the phase 180° or a ‘zero’ by a noninverted carrier phase. The rate of information transmission is one bit per second. For more details, see https:// tsapps.nist.gov/publication/get_pdf. cfm?pub_id=914904 WWVB has identical north and south antennas, each of which is a top-loaded monopole comprising four 122m-tall masts in a diamond shape, with a system of cables suspended between the masts. This is known as a capacitance hat or top hat (see Figs.5 & 6). The down-lead is the radiating element. Two antennas provide higher efficiency than a single antenna. The antennas are 857m apart. Since the wavelength at 60kHz is 5000m, and an antenna should be at least one-quarter wavelength long, theoretically the antenna should be 1250m tall. This is obviously impractical. This antenna is tuned, and the tuning is continuously adjusted under computer-control with a motorised variable inductor called a variometer. This allows it to cope with changing conditions. The use of longwave means that the siliconchip.com.au accuracy of the signal from WWVB is much better than shortwave stations WWV and WWVH (Fig.7), as there is much less multipath propagation. The WWV stations, along with radio amateurs, are also part of the US military’s Military Auxiliary Radio System (MARS). This provides emergency Fig.8: the JJY 60kHz tower at Hagene-yama, Japan with a transmission power of 50kW and an antenna efficiency 45%. The umbrella style mast is 200m high. Signals from this tower are what Australians are most likely to pick up on LF. Australia’s electronics magazine February 2021  13 Fig.9: the signal format of JJY, a variation of IRIG (see below). Source: Wikimedia user Cartoonman. radio backup systems in the event of a communications breakdown such as a major solar flare. There is a history of WWVB at www.ncbi.nlm.nih.gov/pmc/articles/ PMC4487279/ which includes a onetime plan to provide a global timekeeping service at 20kHz. nised to it, including many inexpensive domestic clocks. DFC77 also contains encrypted weather data plus civil defence data, if necessary (see Fig.11). It has been operating in its current format since 1973. standard and are designated A, B, C, D, E, G and H. Stations WWV, WWVH, and WWVB use IRIG H. JJY uses a variant of IRIG. BPC in China The first LF radio-controlled watch was the German Junghans 1990 MEGA 1 (see Fig.13). The first multiband radio-controlled watch was the Citizen model 7400, introduced in 1993. It could receive signals from the major radio time transmitters JJY, DCF77 and MSF but surprisingly, not WWVB (see Fig.14). You can view its PDF manual at http:// siliconchip.com.au/link/ab4w The first watch that synchronised its time via GPS was the Citizen Eco-Drive Satellite Wave Air in 2011; it could acquire a time signal from a GPS satellite in a minimum time of six seconds. JJY has two transmitters at different locations, one on 40kHz and the other on 60kHz (see Fig.8). JJY started as a shortwave broadcaster in 1940, but started transmitting experimental digital time signals on LF in 1966, followed by 40kHz transmissions in 1999 and 60kHz in 2001. The timecode is similar to WWVB, but each bit is inverted in comparison (see Fig.9). BPC is the Chinese 68.5kHz time signal broadcasting service. Its format is proprietary and little is know about it, although its data is known to be transmitted with amplitude modulation plus also spread spectrum. Due to its high power of 90kW, almost double that of JJY in Japan, it can be received in parts of Australia. Perhaps SILICON CHIP readers can see if they can capture it, at least to listen to, if not decode. MSF in the UK Time formats including IRIG MSF started in Rugby 1926, and in 1927, transmitted time signals at 15.8kHz in the form of 306 pulses in the five minutes before 10:00 and 18:00 GMT. In 1966, continuous 60kHz transmissions commenced. The facility was relocated to Anthorn in 2007. It has a transmitter power of 60kW with and ERP of 17kW. The modern MSF time format is shown in Fig.10. IRIG is the Telecommunication Working Group of the American Inter Range Instrumentation Group. Their time code is a standard method for transferring timing information via serial data with a modulated carrier wave over radio, coaxial cable or twisted pair. It can also be transmitted via unmodulated TTL signals over coaxial cable, or differential level shift over RS422 or RS232 (see Fig.12). The original standards were released in 1960 and have been continually updated. Different codes are defined within the JJY in Japan DCF77 in Germany DCF77 is the European 77.5kHz time signal station and it is enormously popular. Numerous devices such as parking meters and traffic lights are synchro- Fig.11: the DCF77 time signal format. It has provision for “meteotime” encrypted weather information and civil defence information. Source: http://arduino-projects4u. com/dcf77/ Fig.10: the MSF time signal format. 14 Silicon Chip Watches that use radio time signals Australia’s electronics magazine siliconchip.com.au Fig.12: the general structure of IRIG codes. Source: www.meinbergglobal.com/english/info/irig.htm The Satellite Wave F100, introduced in 2014, halved that time. The Casio Oceanus is a watch that combines both LF time signal reception and GPS time signal reception (Fig.15). LF works both inside and outside, but if no useful LF signal is present (such as in much of Australia), the Oceanus synchronises via GPS. The Citizen Satellite Wave and the Seiko Astron both synchronise their time via GPS satellites. Unlike watches and clocks that use LF signals, which don’t have universal receiver coverage, GPS signals are available all over the globe. However, they don’t tend to penetrate buildings as well as the LF signals. In practice, this is not really a problem because they will usually be carried outside regularly enough to remain in good synchronisation with GPS time. These watches capture not only the time but their position, so they can adjust to the correct time zone although they don’t indicate position data to the user (see Fig.16). Note that there is an additional category of watches distinct from these such as the Garmin Fenix series which are full-function satellite navigational devices. There is a video showing the inside of a fairly recent radio-controlled watch titled “Tearing Down a Radio Controlled Citizen Eco-Drive” at https:// youtu.be/-gZ8rmEB0ig Important note As there are no LF radio time signals specifically directed towards Australia or New Zealand, if you had one of these radio watches, it is unlikely that you would receive time synchronisation signals at a suitable strength. However, even though Australia and NZ are well out of the intended service range of JJY in Japan, there are numerous reports of JJY signal reception at certain times and in certain locations within Australia. We consider that JJY provides the best chance of receiving a time signal Fig.13 (left): while there were earlier consumer radio-synchronised clocks, this is the world’s first radio-synchronised watch, the Junghans Mega 1, released in 1990. The antenna was in the watchband. The original watch received only European DCF77 time signals. Source: Wikimedia user Pitlane02. Fig.14 (right): the Citizen 7400. Note the large antenna dominating the watch. The antenna is much smaller in more recent watches, and not visible. siliconchip.com.au Australia’s electronics magazine in Australia or New Zealand. While the JJY transmitter is approximately 7773km away from Sydney and 9051km from Auckland; its intended reliable range is only about 1000km. If you want to build some of the experimental circuits mentioned here, they will only work if 1) you can pick up a JJY signal with sufficient strength and 2) they are either designed to work with JJY signals or can be adapted if designed for another station, such as DCF77. Also, note that WWVH on shortwave from Hawaii can be received in Australia and NZ. It is about 8,200km from Sydney. The success of decoding such signals will depend greatly on reception conditions and equipment. Receiving and decoding time signals with software If you can receive an LF or SW radio time signal, you can decode it with your computer sound card and appropriate software. One such program is “Radio Clock” which you can download from www. coaa.co.uk/radioclock.htm (it says it works on Windows 7; we presume it will work on Windows 10 but have not tried it). Another is “Clock” which you can get from http://f6cte.free.fr/ horloge_e.htm This can decode time signals from multiple LF and MF radio clock transmitters, including the ones most likely to be received by Australians and New Zealanders: JJY (LF) and WWVB (SW). It can also decode GPS time from or via RFC868 Internet time server, along with various other methods. Radio clock kits, projects and ICs There are some LF clock kits, modules and ICs available, but since time February 2021  15 Fig.15: a Casio Oceanus OCW-G1000 watch, introduced in 2016. It receives both LF radio and GPS time signals. It follows on from the Casio GPW-1000, introduced in 2014, which was the world’s first watch that could receive both signals. signals are not explicitly directed toward Australia, we cannot guarantee they will work here (see Fig.17). These ideas are for experimenting only. YouTuber Andreas Spiess used a Raspberry Pi and other modules to capture and retransmit a radio time signal for remote control of a clock with no access to the radio signal. In Switzerland, he captures WWVB from the USA (8269km away) but not JJY 60kHz (9388km away). See the video titled “#287 Remote Controller for Clocks” at https://youtu. be/6SHGAEhnsYk A receiver kit (not stand alone) is Fig.16: a Seiko SBXB174 solarpowered, limited-edition GPS watch. available from siliconchip.com.au/ link/ab4x which can be interfaced to an Arduino. Links to code examples are given under “Interesting projects” on that page. Note that this is not suitable for beginners. Erik de Ruiter has developed a very impressive “DCF77 Analyzer / Clock” for the German DCF77 signal using Arduinos (see Fig.18). Full plans are available at siliconchip.com.au/link/ ab4y See the videos titled “DCF77 Analyzer / Clock v.2 demo” at https:// youtu.be/ZadSU_DT-Ks and “DCF77 Analyzer/Clock v2.0 - the inside explained” at https://youtu.be/sPb0La4Qb4 Note that it is unlikely you could receive a sufficiently strong signal Fig.17: this module comprises a ferrite antenna and a circuit board with a MAS6181B1 IC under the ‘blob’. Depending on the module version, it can receive DCF77 and MSF or JJY60 and JJY40 signals. in Australia, but this project demonstrates what can be done. It might be possible to adapt this for JJY reception in Australia. Another clock based on the above design can be seen at www.instructables.com/id/DCF77-Signal-AnalyzerClock/ and in the video titled “Arduino DCF77 Analyzer Clock” at https:// youtu.be/zsiVTP7clQg Simulating an LF signal for watch synchonisation If you are in an area where you can’t receive an LF signal to synchronise your watch reliably or at all, there are some clever apps and hardware that allow you to generate a suitable signal. One method is designed by an Australian and can be found at siliconchip. com.au/link/ab4z It uses a JavaScript program which generates audio signals at 20kHz with 200ms, 500ms and 800ms bursts. The audio signal is fed into an earpiece or wire loop, and an electromagnetic field is generated near the watch. The audio signals produced are Time synchronisation for mobile phones Fig.18: Erik de Ruiter’s home-built DCF77 Analyzer / Clock. 16 Silicon Chip Australia’s electronics magazine Most mobile phones derive their time from either NTP (via the internet) or NITZ (via the mobile phone network). Apple phones use Network Time Protocol time servers which get their time from GPS satellites, while Android phones typically get their time from Network Identity and Time Zone via the mobile networks. This is less accurate, although there are Android Apps to either display or set the time via NTP (warning: some require root access). siliconchip.com.au The Telstra “talking clock” Fig.19: the third harmonic of a square wave is the highest amplitude harmonic, and it is a sinewave at triple the fundamental frequency. So generating a 20kHz square wave pulse results in a 60kHz sinewave approximating the amplitudemodulated JJY time signal. Source: via https://wigglewave.wordpress. com/2014/08/16/pulse-waveforms-and-harmonics/ square waves, and as square waves have strong third harmonic content, the signal includes a significant 60kHz sinewave component (see Fig.19). This signal emulates the JJY time signal from Japan, with the 800ms bursts representing zeros while the 500ms bursts represent ones. The 200ms bursts are marker bits. There are also Android phone Apps such as JJYEmulator, WWVB Emulator and DCF77 Emulator, which are available in the Google Play store for use with Android devices. These work similarly to the JavaScript program, using an earpiece to generate an LF signal to synchronise the watch. Henner Zeller and Anatolii Sakhnik developed a Raspberry Pi based transmitter which emulates either DCF77, MSF, WWVB or JJY and sends a time signal to a watch if you cannot receive an actual radio signal (see Fig.20). See https://github.com/hzeller/txtempus and the video titled “Raspberry Pi DCF77 transmitter setting watch” at https://youtu.be/WzZnGimRj60 Johannes Weber shows how to use a Raspberry Pi with a DCF77 receiver as an NTP server (Internet time server) at http://siliconchip.com.au/link/ab50 It is unlikely you can receive that signal in Australia, but you may be able to adapt these ideas for JJY. Building or buying an antenna for LF reception There are several options for improved time signal reception, such as antennas, but we caution that reception in Australia is not reliable, and these systems should be regarded as experimental. Receiving LF signals requires great attention to minimising sources of electrical noise such as fluorescent lights and switchmode power supplies. Also note that any device you intend to synchronise must have an appropriate time offset capability from UTC for your timezone in Australia. There is an Australian company It used to be possible to dial a phone number and listen to the “talking clock” to get the exact time via recorded voice messages. Originally the phone number was B074 (which became 2074 when alpha prefixes were dropped) but later the universal “talking clock” number was changed to 1194. The automated service started with a mechanical recording from 1954 until 30th September 2019. Before that, a telephone operator read out the time. In September 1990, the mechanically recorded voice was changed to an electronic system. See the news article at siliconchip.com.au/link/ab57 You can listen to an online version at http://1194online.com/ The video titled “electronic talking clock” shows the latest version of the Telstra talking clock, now at the Telstra Museum in Hawthorn, Victoria: https:// youtu.be/BugAJm7-xUM The next video shows the changeover from the old mechanical equipment to the new electronic equipment, which happened in 1990. It is titled “Talking Clock Change Over Sept 1990, Hi Res” and is at https://youtu.be/XNcAJQOCMNo Other radio time transmitters in use around the world Apart from those mentioned, there are some other lesser-known, used or supported time signal transmitters as follows. They are currently active and may make good DX targets or experiment with decoding them. Not all operate full time. • BPM in Pucheng, China at 2.5MHz, 5.0MHz, 10MHz and 15MHz (10-20kW). • BSF in Chung-Li, Taiwan at 77.5kHz (460W ERP). • CHU in Ottawa, Canada at 3.330MHz (3kW), 7.85MHz (10kW) and 14.67MHz (3kW). See siliconchip.com.au/link/ab58 • EBC in San Fernando, Spain at 4.998MHz (1kW). See https://wikimili.com/en/ROA_Time • HLA in Taedok, Republic of Korea at 5MHz (2kW). • IAM in Rome, Italy at 5MHz (1kW). • LOL in Buenos Aires at 5MHz, 10MHz and 15MHz (2kW). • RAB-99 in Khabarovsk, Russia at 25kHz (300kW). • RBU in Moscow, Russia at 66.6kHz (10kW). • RJH-63 in Krasnodar, Russia at 25kHz (300kW). • RJH-69 in Molodechno, Belarus at 25kHz (300kW). • RJH-77 in Arkhangelsk, Russia at 25kHz (300kW). • RJH-86 in Bishkek, Kirgizstan at 25kHz (300kW). • RJH-90 in Nizhni, Novgorod at 25kHz (300kW). • RWM in Moscow, Russia at 4.996MHz (5kW), 9.996MHz (5kW) and 14.996MHz (8kW). • YVTO in Caracas, Venezuala at 5MHz (1kW). siliconchip.com.au Australia’s electronics magazine The Assman digital Talking Clock, now housed in the Victorian Telecommunications Museum February 2021  17 Fig.22: Citizen’s RCW/SU-3 signal enhancer. This is a screengrab from the referenced Russian video. Fig.20: a Raspberry Pi based transmitter for use when no radio signal is present, developed by Henner Zeller and Anatolii Sakhnik. called PK’s Loop Antennas (http:// amradioantennas.com/) which makes loop antenna products including a “Longwave Single Station Loop Antenna for Portables”. This is custom-made for specific frequencies such as 40kHz, 60kHz or 77.5kHz although it is not specifically marketed for its ability to receive time signals in Australia (see Fig.21). It is inductively coupled to a watch or clock. Given an interference-free environment, that antenna could assist in synchronising a radio-controlled watch or clock in Australia for JJY at 60kHz, which is the more reliable frequency for local reception. In Melbourne, JJY is best received from 8pm to midnight in winter. Clint Turner (KA7OEI) has described “a remote antenna for 60 kHz WWVB reception” at www.ka7oei. com/wwvb_antenna.html It is a remote antenna for use when Fig.21: an inductively-coupled 60kHz loop antenna from the Australian company PK’s Loop Antennas. This could be used to help a watch or clock receive the Japanese JJY time signal in Australia, in the right circumstances. suitable reception is not available for a radio-controlled timekeeping device inside a building. It is designed for WWVB reception but is described as also being able to receive JJY or MSF at 60kHz. It can also pick up JJY at 40kHz and DFC77 at 77.5kHz with appropriate adjustments to the resonant frequencies of the loops. YouTuber “Watch Geek” describes a remarkably simple method to enhance reception in watches without electronics. This person lives at the reception edge of DFC77, but the technique might work elsewhere. It involves attaching the watch to a large metal object such as a bicycle or metal pipe which acts as an antenna. In the comments, a user in Brisbane says it worked for them. See the video titled “DIY Amplifier for Atomic Radio Controlled watches that actually works & is VERY simple” at https:// youtu.be/wI4FwQMCN9w Citizen used to (and possibly still does) produce a passive antenna de- vice to amplify the DCF77 77.5kHz radio time signals for its watches (see Fig.22). It has been described as a tuned inductive coil around a ferrite core. The watch is placed near it for an enhanced signal. The model code is RCW/SU-3, and it works for all brands of radio-controlled watches. It was supplied free with some Citizen watches. We don’t know how well it would work for 60kHz signals. A Russian YouTube video on the device titled “Citizen Wave Receiver RCW/SU-3” can be viewed at https:// youtu.be/dQAesLWaCxY Note that you can use YouTube settings to automatically translate and generate English subtitles. Enhancing reception You may be able to enhance radio signal reception of a watch by placing it at the centre of a resonant loop antenna. The ends of the wire loop are connected with a capacitor to make a tank circuit; no connection to the watch is needed. It is the same principle of inductive coupling as used by some loop antennas for AM broadcastband radios. We found the following two ideas interesting, but we haven’t tried them ourselves. 1) At http://siliconchip.com.au/ link/ab51 Ivan describes the follow- Online software-defined radio (SDR) in Melbourne To try to receive and hear some time signals, you can visit http://sdr-amradio antennas.com:8071 (see right). This is an online SDR located in Croydon, Melbourne. A time code filter is also available for some modes. Naturally, you can receive a wide variety of other frequencies as well from about 12kHz to 30MHz. 18 Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.24: the Nitsuki 7572B generates time and frequency reference signals from JJY in Japan on 40kHz and 60kHz. It provides 5MHz and 10MHz outputs with an accuracy of up to Up to 3 parts in 1012. It also has a built-in rubidium oscillator. 84mm (3.3 inches) wide, ie, 3mm x 28 turns. Fig.23: a 60kHz passive loop antenna designed by Australian Pete_JBK and described at siliconchip.com.au/link/ ab52 ing loop antenna: “… make a rectangular coil, about one foot by one foot, some 30 turns wound by a fairly thin magnet wire (#25 to #30). Bring it into resonance at 60kHz by a capacitor, some 8000-10000pF. Place the coil vertically, aiming to the transmitter, and place the clock to its center. You do not need any mods of the clock. The signal should be significantly stronger.” 2) Australian Pete_JBK posted plans for a loop antenna design to enhance watch reception – see it at siliconchip.com.au/link/ab52 In summary, this design uses two pieces of wood 52x120x20mm, joined to make an “X”, as a frame for wire (diameter not specified) that is 28 loops measuring 254x254mm with 3mm spacings (see Fig.23). The two ends are terminated with a capacitor of unspecified value. Using online calculators for square loop antennas at http://earmark. net/gesr/loop/joe_carr_calc.htm and https://earmark.net/gesr/loop/, we estimate that the capacitor for approximate 40kHz resonance would be 53nF, or for 60kHz, it would be 23nF. This is based upon the loop being 25.4 x 25.4cm (10 inches square) and Other uses for time signals Time signals have also been used for surveying and astronomical work in Australia for a long time. For example, JJY and WWVH are mentioned in a 1964 paper on correcting astronomical observations, which you can read at http://xnatmap.org/report_tdnm/ agb%20smcorn%20astro.pdf Time signals can also be used as a frequency standard (see Fig.24). Work described at siliconchip.com. au/link/ab53 involves simultaneous reception of GPS and LF radio signals to make propagation time measurements in the ionosphere. This allows ionospheric physics and the interaction of cosmic rays in the ionosphere to be studied. Accuracy of time signals The time and frequency standards for radio clock broadcasts are incredibly accurate, but keep in mind that there will be inaccuracies at the receiver. For example, a distance of 1000km from the transmitter will result in a 3ms delay due to the speed of light. Plus, in theory, a receiver will take one half of the signal period to synchronise, so, in the case of DCF77 at 77kHz, this would take 6.452µs. There are also inaccuracies introduced due to skywaves and groundwaves overlapping due to slightly dif- Fig.25: the Meinberg GEN170 timecode generator for testing DCF77-receiving equipment. ferent path lengths. But all these inaccuracies are of little consequence for most users. JJY has frequency stability of 1 part in 1011, WWVB has frequency stability on the carrier of 1 part in 1014, giving a time within 100ns of UTC and 20ns of US national time standards. DCF77 has a carrier frequency stability of 0.5 in 1012 over 24 hours, and no gain or loss of one second in 300,000 years. MSF has a carrier frequency stability of 2 parts in 1012. Specialised devices are or were available for testing receiver operation, such as the Meinberg GEN170 timecode generator (see Fig.25). Antennas used in watches Few details of the exact nature of the miniature antennas and receiving circuitry used in LF radio-controlled watches have been published. We think they are a type of highly-tuned magnetic core loop antenna (MCLA) with the core being ferrite or similar material (see Fig.26). These would then feed a differential amplifier which uses weak-signal techniques. The academic paper at siliconchip. com.au/link/ab54 has some information on simulating the performance of these types of antennas while another paper at siliconchip.com.au/link/ab55 has details on performance evaluation. One of the authors is from Casio. Fig.26: the evolution of Citizen radio controlled watch antennas. Source: Citizen. siliconchip.com.au Australia’s electronics magazine February 2021  19 Fig.27: some radio clock modules and ferrite antennas from commercial radio clocks. When these were removed, the digital clocks continued to function normally but without radio synchronisation. An amorphous metal or “metallic glass” core is discussed in the second paper as being superior to ferrite. To give an idea of the size of these antennas, one is mentioned in the second paper as being 16mm long with 1107 turns of 0.08mm diameter copper wire, with a core relative permeability of 8000 and an antenna factor of 30-40dB/m. Another antenna mentioned in the Videos on radio time signals Changing a Regular Clock to a Radio Controlled ‘Atomic’ Clock” – https://youtu.be/yll9ZzFnFqA You can find these movements online if you Google “radio clock movement” or “atomic clock movement”. You can also buy online (for less than AU$20) radio clock movements for all the common LF radio time signals, including WWVB, JJY, MSF, DCF77. An Australian, N. May (VK3NM) listens to JJY (LF) from Melb o u r n e : “ J J Y 6 0 k H z ” –    https://youtu.be/ZllHMZmDdKs A video of WWVH (SW) signals being received in Australia: “WWVH Time signal 10000Khz 18-11-2013” – https://youtu.be/pYnZF8VENmQ Fig.28: an inexpensive (US$19.94 on Amazon) consumer radio clock available in the USA. This clock synchronises only from WWVB in Fort Collins, Colorado. It is unlikely to receive a suitable signal in Australia. The symbol above the colon indicates that a radio signal is being received. first paper has a core 1.1mm x 16mm with 103 turns of 0.08mm diameter wire over 11mm of the core. The original radio controlled watch from 1990, the Junghans Mega 1, had a straight-wire antenna in the band. What’s inside a commercial radio clock? Arduino forum contributor ChrisTenone purchased some inexpensive consumer radio clocks in the USA and found the modules shown in Fig.27 inside. See siliconchip.com.au/link/ ab56 for more details. Figs.28-32 show current model radio clocks and two of historical interest. Radio time in Australia It’s a great shame that Australia doesn’t have such a service. It would probably save a lot of time(!) and money compared to manually setting the time on equipment, or doing it automatically by other methods. You may recall that Australia once had a tower which was used for the now-obsolete Omega Navigation Sys- A look at the radio clock module in a European clock: “Having fun with a 10 euro DCF77 clock - better than bare modules?” https://youtu.be/CnWuUlvN3bY Another look at the radio module in a European clock: “From the Lidl non-food Aisle: DCF77 Radio Controlled Clock” – https://youtu.be/OsVt3JCrGV 20 Silicon Chip Fig.30: a 1983 Heath GC-1000 clock. It used SW time synchronisation signals at 5MHz, 10MHz or 15MHz rather than LF. See the video titled “Heathkit GC-1000 most accurate clock demo” at https://youtu.be/WCP9dVtUJXI Australia’s electronics magazine Fig.29: the German Junghans Mega desktop clock from 1991. This particular one was tuned to the 60kHz MSF signal which was from Rugby, UK at the time. Other versions were for DCF77. It was one of the first, if not the first LF radio-controlled clock produced for home use. tem in Woodside, Victoria, that could have been repurposed for LF time signals. But that was demolished in 2015 after the government decided that they no longer had any use for it (see the article on Omega in SILICON CHIP, September 2014; siliconchip.com.au/ Article/8002). SC Fig.31: a rather blurry photo of a vintage Precision Standard Time Model 1020 WWV, which had various computer interface options for controlling equipment. This one is probably from the late 1980s. Source: Brooke Clarke, N6GCE. Fig.32: there’s quite a bit of circuitry on several sub-boards in the Heath GC-1000. It was available either prebuilt or as a kit (you might have heard of Heathkit). This is a screengrab of a comprehensive teardown/upgrade video you can view at https://youtu.be/ YpVSGYy4iH0 siliconchip.com.au