US Coast Guard Radio Station NMC: Summer of 2003


Many thanks to SRAA contributor, Bruce Atchison, for sharing the following recording and notes:

As for radio station NMC, I forget the frequency. It was somewhere in the aircraft band, somewhere about 8000KHZ. I used a Kenwood TS440S transceiver and I believe it was taped in the summer of 2003. Sorry I can't be more exact.

NIST Radio Station WWVH as it sounded in the 1980s


Many thanks to SRAA contributor, Myke Dodge Weiskopf, who shares the following recording and notes:

NIST Radio Station WWVH as it sounded in the 1980s. To contrast with other recordings of the WWVH station ID, note that announcer Jane Barbe does not say (her now-famous) “Aloha!” at the end of this version.
This recording was found at WWVH in 2015 on an undated cassette labeled “JB on Old Audichron TCG” (which stands for Time Code Generator, the device which reconstructs and plays back Jane’s voice over the air). As such, the precise broadcast year is not known, but it is consistent with the voice and broadcast format of the 1980s, until the introduction of the short-lived digital voice in 1991.
An excerpted version of this recording is found on "At the Tone: A Little History of NIST Radio Stations WWV & WWVH." This unedited version is being shared by special arrangement for the Shortwave Archive.

WWV Time Station (15 MHz): November 3, 2017


Many thanks to SRAA contributor, Emilio Ruiz, who shares the following recording of WWV and notes:

Sad for the news, the closing of WWV is like close a park, a comunity place where scientifics and enthusiast of radio could learn and experiment not only about time, radio propagation too. I not have much money for bought radiofrecuency equipment for repair or make my own radios, i use WWV for that. 
To go to the future it is not necessary to destroy the past, I'm teaching to children about science and technology and when talk about radio share with they the listen of WWV with old radio receiver (BC-548Q), for they the sound of ticks and the history about radio and time is a amazing topic.
I wrote this review (in Spanish) about WWV for those SWListeners and Radio Amateurs who do not spoke English,--I think can be useful.
I hope radioamateurs of U.S. can reverse the decision.
Broadcaster: WWV
Date of recording: 11/3/2017
Starting time: 14:00
Frequency: 15000 kHz
Reception location: Chiapas, México.
Receiver and antenna: Dipole antenna, Keenwood R-600

USAF EAM Voice Transmission: June 27, 2016

Many thanks to SRAA contributor, John Lutz, who notes:

Emergency Action Message (EAM) transmissions are associated with the High Frequency Global Communications System (HFGCS). The HFGCS is a network of single sideband transmitters used by the United States Air Force to transmit encrypted messages to in-flight military aircraft, ground stations and in some cases, US Navy surface vessels. The purpose and format of the messages are subject to wide-ranging speculation, but are generally thought to be for directing nuclear-capable forces regarding the execution of specific attack options.
Starting time: 04:52 UTC
Frequency: 8.992 MHz
Location: Shorewood, IL EN51vm
Receiver and antenna: FT-920 transceiver and ground-mounted 23-foot vertical antenna

Gulf Harbour Radio: June 22, 2016

ZMH286 Gulf Harbour Radio reporting weather and sailing conditions and communicating with yachts sailing in the South Pacific. Broadcast at 1915 UTC Monday to Saturday, from May to November. Transmitted from Whangaparaoa, New Zealand, kw unknown. In association with Yachts in Transit, There are some deep fades during the transmission. Received in Sydney, Australia, with a Sangean ATS-909X and PK's mag loop antenna.

Radio Reloj: August 30, 2015

Many thanks to SRAA contributor, Richard Langley, who notes:

Live recording of Radio Reloj (CMBD), Havana, Cuba, on 30 August 2015 beginning at about 15:55 UTC on a frequency of 950 kHz. The signal originates from a 10 kW transmitter at Arroyo Arenas / San Augustin, near Havana, using the Centros Transmisores de Ondas Medias 1 (CTOM1) non-directional antenna facility.

(Radio Reloj can be heard on various frequencies in the AM and FM bands in Cuba and live on the Internet at 

The recording, in Spanish, is a typical Radio Reloj broadcast with two announcers alternately reading news bulletins accompanied by time signals. The announcers identify the station and verbally give the local time each minute. In addition to the verbal station identification, each minute either the letters RR in morse code (using 1800 Hz tones) are transmitted or five-note chimes (D4, G4, B4, D5, B4) are played. The chimes sound like those of a dinner chime or even some door bells and are reminiscent of the U.S. National Broadcasting Company (NBC) chimes. On a couple of occasions in this recording, during a particular minute, neither the morse code nor the chimes are used and sometimes, during a particular minute, both are used. In this recording, we can also hear at some minutes pairs of tones being played going up and down the scale as news headlines are read. On other occasions, three- and four-note chimes in various sequences have been heard (perhaps at the announcers' whim).

Different tones identify each second, minute, and five-minute epochs. Based on measurements, each second is marked with a "seconds tick" consisting 10 cycles of a 1000 Hz tone (0.01 seconds duration). Minutes, except for multiples of 5 minutes, are marked by 172 cycles of a 1000 Hz tone (0.172 seconds duration). Every 5 minutes, the marker is extended to 672 cycles of a 1000 Hz tone (0.672 seconds duration). The minute and 5-minute markers are preceded by 5 cycles of a 1000 Hz tone, followed by 0.013 seconds of silence.

The time signals in this particular broadcast were well within one second of the time given by a computer's clock synchronized to the U.S. time standard using Network Time Protocol. 

The broadcast was received on a Tecsun PL-880 receiver with its built-in loop antenna in Key West, Florida, using an RF bandwidth of 5 kHz. The receiver was oriented for maximum signal strength. Signal quality is generally good. However, there are repeated static crashes (QRN) from thunderstorms in the region.

Richard also notes that he was located in Key West, Florida, using  a "Tecsun PL-880 receiver with built-in loop antenna using an RF bandwidth of 5 kHz. The receiver was oriented for maximum signal strength." 

1981 & 1982: Various International Time Signal Stations

One of four WWV time code generators in late August, 2014 (Photo: Thomas Witherspoon)

One of four WWV time code generators in late August, 2014 (Photo: Thomas Witherspoon)

Many thanks to SRAA contributor, Tom Laskowski, who shares the following recordings he has transferred from audio cassette. Tom includes the following notes:

I combined several audio files of some of the common time signal stations available back in 1981 and 1982 into one clip. These were made using a DX-302 which had poor image rejection and you can hear some stations behind WWV which shouldn't be there, such as RCI's interval signal at one point.

00:00 - VNG, Australia - August 16, 1981 on 12.000 MHz at ???? UTC
03:02 - LOL, Argentina - October 15, 1981 on 15.000 MHz at 2349 UTC
07:27 - BPM, China - January 16, 1982 on 10.000 MHz at 1255 UTC
08:38 - ZUO, South Africa - December 18, 1982 on 5.000 MHz at 0329 UTC

1991 cassette of shortwave IDs, interval signals and numbers stations

SWLing Post reader and SRAA contributor, Frank, writes from Germany:

First let me say that I enjoy your blog a lot.

After a 2005-13 hiatus, I have rediscovered a childhood hobby and your reviews have helped me find my way to the post-Sony portable shortwave radio markets.

First, I obtained my “childhood dream” radio (Sony ICF 2001D), because at the time I made these recordings I was still in school and 1300 DM would have equaled over 1 year of pocket money, so a Supertech SR16HN had to do. I thought I got some fine results with this Sangean-Siemens re-branded receiver then, using a CB half-length antenna, a random wire, and much endurance.

I kept regular logs throughout the years, wrote to 50 international and pirate stations for QSL and compiled this cassette.

A few years before I got that trusty SR16HN, however, I recorded a few number stations (such as G3, Four Note Rising Scale etc) with an ordinary radio cassette recorder, and in 1991 I put them onto this tape as well. The other recordings are done with the same radio placed right in front of the SR 16HN.

Feel free to make use of these recordings. Most of it are the well-known international state-owned shortwave stations of the past; plus European pirates; plus number stations; and at the end, a few (off-topic) local Am and FM stations interval signals.

As I said, this collection I made shortly after the Wende/reunification period, when all former-GDR state broadcasters changed their names, sometimes more than once.

Please continue your good work on the blogs! Weather permitting I am often outside cycling and always have the tiny Sony ICF 100 with me (which I call my then-student’s dream radio of the later 90ies).

Cassette Side 1

Cassette Side 2

WWV changes announcement format: July 1, 1971

Shortwave Radio Audio Archive contributor, Brian D. Smith, recently contacted me; I was enthused when he described the recording he was sharing:

"This recording captures the last 5 minutes of WWV’s old format (giving the time every 5 minutes) and the first 5 minutes of the new format (giving the time every 1 minute), which took place on July 1, 1971 UTC.

Apologies for the less-than-stellar audio quality, but I recorded this as a 15-year-old fledgling SWL with limited knowledge of audio recording techniques. So I simply placed the microphone from my cassette tape recorder next to the speaker on the receiver and hit the record button. The signal quality wasn’t the greatest, either — lots of QSB and QRM — but I still managed to get what I was going for.

The resulting recording has accompanied me everywhere since then, preserved only on its original cassette, until 2008, when I finally decided it was time to learn how to transfer it onto my hard drive, burn it onto a CD and stop having to rely on the integrity of 37-year-old audio tape.

Even as a teenager, I regarded the WWV changeover as historic, and felt I should attempt to record it for posterity. Consider yourself posterity!"

Brian received this broadcast on 10 MHz care of a Hallicrafters S-108, with random length of wire attached to the back of the receiver serving as an antenna. Location was Franklin, Indiana.

As Brian mentions, the audio quality is a little rough, but this is still quite a treasure of a recording!

Click here to download as an MP3, or simply listen via the embedded player below:

CHU Canada, Leap Second: June 30, 2015

(Image: NASA)

(Image: NASA)

SRAA contributor, Richard Langley, writes:

Live recording of time signal station CHU, Canada, on 30 June 2015 beginning at exactly 23:55:00 UTC on a frequency of 7850 kHz. The recording last exactly 10 minutes and 1 second, ending at 0:10:00 UTC. A leap second occurs at 23:59:60 UTC. This can be noted by the 1 second of silence between the 5m:00s mark in the recording (23:59:60 UTC) and the 5m:01s mark (0:00:00 UTC) denoted by the start of the one-second-long tone. This is followed by 9 seconds of silence. Before the leap second, the forecast difference between UT1 and UTC (DUT1 = UT1 minus UTC) to a precision of one tenth of a second was -0.7 seconds. This is indicated by CHU by using a sequence of double tones at 9 seconds through 15 seconds after the start of each minute except for the minute beginning an hour. Following the leap second, DUT1 is +0.3 seconds, marked by double tones at 2 seconds through 4 seconds after the start of the minute, again, except for the minute beginning an hour. 

The strong CHU signal was received on a Tecsun PL-880 receiver with a Tecsun AN-03L 7-metre wire antenna in Hanwell, New Brunswick, Canada, in AM mode with 5 kHz RF filtering. There is some atmospheric noise (static).

Recording the 2015 Leap Second via WWV and CHU: June 30, 2015

OOne of four WWV time code generators in late August, 2014

OOne of four WWV time code generators in late August, 2014

Yesterday, I posted a brief article about the leap second that occurred between 23:59:59 June 30, 2015 and 00:00:00 UTC July 01, 2015.

I decided to record the leap second on as many shortwave time station frequencies as possible. The only viable options for me--based on time of day and my reception location--were the WWV frequencies 10, 15, 20, and 25 MHz, and CHU frequencies 7,850 and 14,670 kHz.

I was able to monitor four different time station frequencies simultaneously on the TitanSDR Pro. (click to enlarge)

I was able to monitor four different time station frequencies simultaneously on the TitanSDR Pro. (click to enlarge)

Unfortunately, HF propagation was very poor yesterday, so the higher WWV frequencies--20 and 25 MHz--were completely inaudible, as was CHU on 14,670 kHz. There were numerous thunderstorms in our area, so static crashes were prevalent.

Still, since this was a first attempt to record a "leap second," I didn't want to take any chances.  I had the Titan SDR Pro monitoring and recording two CHU and two WWV frequencies [screenshot], the Elad FDM-S2 recording WWV on 15 MHz [screenshot], and the WinRadio Excalibur on WWV's 10 MHz frequency, as well as recording the whole 31 meter band spectrum [screenshot].

In the end, the strongest frequencies I captured were CHU on 7,850 kHz and WWV on 15,000 kHz. WWV on 10,000 kHz was much weaker than normal and the band was quite noisy--still, it's readable, so I included this recording, too. Recordings follow...


The sign above WWV's primary 10 MHz transmitter (2014).

The sign above WWV's primary 10 MHz transmitter (2014).

All of the recordings start just before the announcement of 23:59 UTC.

WWV added the extra second and higher tone, then continued with their top of the hour announcements, including a note about leap second (which begins after the 00:04 announcement). CHU's adjustment included a long second tone and period of silence.

WWV on 15,000 kHz using the Elad FDM-S2:

CHU on 7,850 kHz using the TitanSDR Pro:

WWV on 10,000 kHz using the WinRadio Excalibur:

One interesting note about the 10 MHz WWV recording above: I believe I may be hearing BPM China in the background. I'm curious if anyone can confirm this because I don't know BPM's cadence/pattern well enough to ID it.