Radio signals during a leap second
This web page documents what many radio stations (mostly broadcast) did
during the leap second
at the end of 2008.
Many broadcasters transmit time pips (e.g., 6 pips at 1 second intervals, or 2 short pips followed by 1 long beep)
at the top of the hour. These may sound very precise, with the hour starting
precisely at the beginning of the last pip, but it turns out that many
of them are actually quite inaccurate.
(For a similar set of measurements of the 2005 leap second, but limited to the longwave
range, see here.)
Time/frequency reference stations: DCF77 and RWM
Like in the previous leap second, the German longwave transmitter on 77.5 kHz
got it right:
Like all other diagrams on this page, this is a so-called waterfall diagram, which shows
the signal strength (by color, from black via blue and pink to white) as
a function of frequency (horizontal axis) and time (vertical axis).
The Russian time signal on 4996 kHz also got it right:
My recordings also covered MSF, HBG, WWV and CHU's frequencies,
but those signals were too weak to be discerned.
Longwave broadcast stations
In Europe, there is a longwave broadcast band between 148.5 to 283.5 kHz.
These transmitters use amplitude modulation to transmit audio to the general public,
and thus are not necessarily precion time and frequency reference stations.
However, many do transmit time signals in the form of 1 kHz beeps at the top of
the hour. These can easily be seen in the waterfall diagram.
Here's the waterfall diagram of this band during the 2008 leap second:
(A similar picture of the situation 1 hour earlier is here.)
|153 kHz||Deutschlandfunk, Germany||
Leapsecond ok, although it seems a fraction of a second early, but in the previous hour the time signal was 1 second early!
|177 kHz||Deutschlandradio Kultur, Germany||
Broadcast two long beeps, 1 and 2 seconds too late.
In the previous hour, the only long beep was 2 seconds late.
So apparently their clock is 2 seconds late (or there is 2 seconds of delay
in their transmitting system), but did capture the leap second.
No time beeps, but the bell sound starts exactly on time after the leap second.
|207 kHz||Deutschlandfunk, Germany||
Missed the leap second.
|252 kHz||Ireland & Algeria||
Time signal is more than 5 seconds late!
An hour earlier it was 6 seconds late, so they didn't insert the leap second.
An Irish reader of this page (see here for his leapsecond observations)
pointed out that the Irish station did not send any time pips,
so the visible late time signal those must have come from the Algerian station.
Listening to the demodulated recording, one can hear both stations,
with a voice count-down from Ireland and pips plus a French announcement
Missed the leap second.
Was 3 seconds early.
So out of 8 stations transmitting a time signal, only 3 got it right.
Mediumwave broadcast stations
Here's a picture of the center 600 kHz of the mediumwave broadcast band:
Correct leap second:
Time signals without leap second:
- 756 kHz
- 819 kHz; one pip skipped at 23:59:59z
- 891 kHz
- 900 kHz; one pip skipped at 23:59:59z
- 936 kHz
- 972 kHz
- 990 kHz
- 1026 kHz
- 1044 kHz
- 1080 kHz
- 1116 kHz
- 1188 kHz (no pips, but announcement "Ein Uhr" was on time)
- 1269 kHz
- 1287 kHz; one pip skipped at 23:59:60z
- 720 kHz
- 747 kHz (and/but almost half a second late)
- 783 kHz (no time pips, but the announcement "Ein Uhr" was early)
- 882 kHz
- 954 kHz
- 963 kHz
- 1071 kHz
- 1197 kHz
Not all of the above observations can be derived from the graph; some are too weak to
be visible in this graph, but were observed in a more zoomed-in graph and/or
- 909 kHz, almost 1 second late
- 981 kHz, 3 seconds late
- 1143 kHz, 2 seconds late
Conclusion: about half of the stations got the leap second right.
Note, both here and in the longwave plot, that the time signals are not
always precise to a fraction of a second, presumably due to delays in the
distribution networks (e.g., satellite links). An extreme case is the
(Dutch) station on 747 kHz.
Shortwave broadcast stations
Waterfall diagrams of the 49 m and 41 m shortwave broadcast bands
Again, some got it right, and some didn't.
All of the above pictures were made using the latest version of
my home-built Software-Defined Radio system,
I used this to record six parts of the radio spectrum, with a total
bandwidth of 1.8 MHz.
(Actually, the system could have recorded an even larger bandwidth,
if the power supply had not been insufficient, which forced me to run
the ethernet connection to the PC on 100Mbit/s instead of 1 Gbit/s.)
The antenna was a dipole for the 40 m band, aided (for the lower
frequencies) by a ground connection.
Comments are welcome, at