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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.
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Australia’s electronics magazine
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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
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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.
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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.
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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
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