Stations
HF time & frequency stations

HF Time & Frequency Standard Stations

The stations below are widely used to check current radio propagation conditions.

The primary functions of WWV and WWVH are to transmit official standard time on highly accurate reference frequencies traceable to the U.S. national standard. Other stations listed below serve similar functions in other countries.

In addition to those primary functions, these stations serve another important function in providing means to quickly check radio propagation conditions from multiple locations on a variety of widely spaced frequencies. That function is especially important to radio amateurs, shortwave listeners, and others interested in radio propagation. These stations serve that function better than most other shortwave stations, because they transmit constantly from known locations with known power levels using known antenna systems.

Time & Frequency Standard Stations
Freq. Call Power Distance Description
2500 kHz WWV
WWVH

2.5 KW
5 KW

358 Miles
3070 Miles

WWV Broadcasts National Institute of Standards and Technology (NIST) time and frequency signals from a location near Fort Collins, Colorado. WWV uses a male voice.

WWVH Broadcasts National Institute of Standards and Technology (NIST) time and frequency signals from a site near Kekaha at Kokole Point on the Island of Kauai, Hawaii. WWVH uses a female voice.

For both stations the transmission mode is DSB AM. Steady tone modulation is 50%. BCD time code modulation is 50%. Second pulses and minute and hour marker modulation 100%. Voice modulation is 50%. The antenna polarization is vertical.

WWV and WWVH share 2500 kHz with BPM, Shaanxi Astronomical Observatory, Chinese Academy of Sciences, P.O. Box 18 - Lintong, Shaanxi, China. (See Double Time Markers)

3330 kHz CHU 3 KW 1830 Miles Broadcasts National Research Council (NRC) of Canada time and frequency signals from a site 15 km southwest of Ottawa, Ontario, Canada. The transmission mode is USB with carrier re-inserted to enable reception by AM receivers. The antenna polarization is vertical.
3810 kHz HD2 IOA 1 KW 3375 Miles Ecuadorian Military Navy time and frequency standard station transmits one-second tone-pulse time-markers and local time announcements in Spanish between 19:00 to 07:00 UTC from the Instituto Oceanográfico de the Armada in Guayaquil, Ecuador. The one-second tone-pulse time-markers are 600 Hz the first 15 minutes, 400 Hz the second 15 minutes, and are omitted the last 30 minutes of each hour. Station identification is transmitted every hour between 40 minutes and 59 seconds and 59 minutes and 40 seconds. The signal strength is typically about S7 in Salt Lake City during winter nights when the skip is long, but transmissions sometimes are difficult to hear because of strong interference from U.S. Amateur Radio stations.
4996 kHz RWM Unknown 5550 Miles Institute of Metrology for Time and Space (IMVP), GP "VNIIFTRI", Mendeleevo, Moscow Region 141570, Russia
4998 kHz EBC 10 KW 5350 Miles Real Instituto y Observatorio de la Armada - 11100 San Fernando, Cadiz, Spain
5000 kHz WWV
WWVH
10 KW
10 KW
358 Miles
3070 Miles

WWV Broadcasts National Institute of Standards and Technology (NIST) time and frequency signals from a location near Fort Collins, Colorado. WWV uses a male voice.

WWVH Broadcasts National Institute of Standards and Technology (NIST) time and frequency signals from a site near Kekaha at Kokole Point on the Island of Kauai, Hawaii. WWVH uses a female voice.

For both stations the transmission mode is DSB AM. Steady tone modulation is 50%. BCD time code modulation is 50%. Second pulses and minute and hour marker modulation 100%. Voice modulation is 50%. The antenna polarization is vertical.

WWV and WWVH share 5000 kHz with the following stations:

BSF, Telecommunication Laboratories, National Standard Time and Frequency Laboratory, Chunghwa Telecom. Co. Ltd., P.O.Box 71-Chung-Li, 320 Taiwan, Republic of China

BPM, Shaanxi Astronomical Observatory, Chinese Academy of Sciences, P.O. Box 18 - Lintong, Shaanxi, China (See Double Time Markers)

HLA, Time and Frequency Laboratory, Korea Research Institute of Standards and Science, Yusong P.O. Box 102, Taejon 305-600, Republic of Korea

IAM, Istituto Superiore delle Comunicazioni e delle Techologie dell’Informazione, Viale America 201, 00144 - Rome, Italy

LDS, School of Electronic and Electrical Engineering, Leeds University, Leeds, LS2 9JT United Kingdom

LOL, Servicio de Hidrografia Naval, Observatorio Naval, Av. España 2099,1 107 Buenos-Aires, Argentina

YVTO, Direccion de Hidrografia y Navegacion, Observatorio Cagigal, Apartado Postal No 6745, Caracas, Venezuela

7850 kHz CHU 10 KW 1830 Miles Broadcasts National Research Council (NRC) of Canada time and frequency signals from a site 15 km southwest of Ottawa, Ontario, Canada. The transmission mode is USB with carrier re-inserted to enable reception by AM receivers. The antenna polarization is vertical.
9996 kHz RWM Unknown 5550 Miles Institute of Metrology for Time and Space (IMVP), GP "VNIIFTRI", Mendeleevo, Moscow Region 141570, Russia
10000 kHz WWV
WWVH
10 KW
10 KW
358 Miles
3070 Miles

WWV Broadcasts National Institute of Standards and Technology (NIST) time and frequency signals from a location near Fort Collins, Colorado. WWV uses a male voice.

WWVH Broadcasts National Institute of Standards and Technology (NIST) time and frequency signals from a site near Kekaha at Kokole Point on the Island of Kauai, Hawaii. WWVH uses a female voice.

For both stations the transmission mode is DSB AM. Steady tone modulation is 50%. BCD time code modulation is 50%. Second pulses and minute and hour marker modulation 100%. Voice modulation is 50%. The antenna polarization is vertical.

WWV and WWVH share 10000 kHz with the following stations:

ATA, National Physical Laboratory, Dr K.S. Krishnan Road, New Delhi - 110012, India

BPM, Shaanxi Astronomical Observatory, Chinese Academy of Sciences, P.O. Box 18 - Lintong, Shaanxi, China. (See Double Time Markers)

LOL, Servicio de Hidrografia Naval, Observatorio Naval, Av. España 2099,1 107 Buenos-Aires, Argentina

(Many Indonesian fishing vessels ignore international frequency allocations and use 10000 kHz as a communication channel. Their chatter sometimes can be heard in the background when the skip is long at that frequency.)

14670 kHz CHU 3 KW 1830 Miles Broadcasts National Research Council (NRC) of Canada time and frequency signals from a site 15 km southwest of Ottawa, Ontario, Canada. The transmission mode is USB with carrier re-inserted to enable reception by AM receivers. The antenna polarization is vertical.
14996 kHz RWM Unknown 5550 Miles Institute of Metrology for Time and Space (IMVP), GP "VNIIFTRI", Mendeleevo, Moscow Region 141570, Russia
15000 kHz WWV
WWVH
10 KW
10 KW
358 Miles
3070 Miles

WWV Broadcasts National Institute of Standards and Technology (NIST) time and frequency signals from a location near Fort Collins, Colorado. WWV uses a male voice.

WWVH Broadcasts National Institute of Standards and Technology (NIST) time and frequency signals from a site near Kekaha at Kokole Point on the Island of Kauai, Hawaii. WWVH uses a female voice. WWVH 15 MHz antenna array information and photo

For both stations the transmission mode is DSB AM. Steady tone modulation is 50%. BCD time code modulation is 50%. Second pulses and minute and hour marker modulation 100%. Voice modulation is 50%. The antenna polarization is vertical.

WWV and WWVH share 15000 kHz with the following stations:

BSF, Telecommunication Laboratories, National Standard Time and Frequency Laboratory, Chunghwa Telecom. Co. Ltd., P.O.Box 71-Chung-Li, 320 Taiwan, Republic of China

BPM, Shaanxi Astronomical Observatory, Chinese Academy of Sciences, P.O. Box 18 - Lintong, Shaanxi, China. (See Double Time Markers)

LOL, Servicio de Hidrografia Naval, Observatorio Naval, Av. España 2099,1 107 Buenos-Aires, Argentina

15006 kHz EBC 10 KW 5350 Miles Real Instituto y Observatorio de la Armada - 11100 San Fernando, Cadiz, Spain
20000 kHz WWV 2.5 KW 358 Miles WWV Broadcasts National Institute of Standards and Technology (NIST) time and frequency signals from a location near Fort Collins, Colorado. WWV uses a male voice. The transmission mode is DSB AM. Steady tone modulation is 50%. BCD time code modulation is 50%. Second pulses and minute and hour marker modulation 100%. Voice modulation is 50%. The antenna polarization is vertical. (Rarely receivable in Salt Lake City, because the 20 MHz skip distance usually exceeds 358 miles.)

Double Second Time Markers
Other International time and frequency standard stations share 2500, 5000, 10000, and 15000 kHz. Sometimes they can be heard from Salt Lake City when the skip distance is long. One of those stations is BPM in Pucheng, China, which is operated by the Chinese National Time Service Center (NTSC) (Shaanxi Astronomical Observatory, Chinese Academy of Sciences). BPM usually broadcasts Coordinated Universal Time (UTC) like WWV and WWVH do, but during minutes 25 through 29 and 55 through 59 of each hour BPM transmits UT1 instead. UT1 varies up to 0.9 second from UTC and the time difference can be either positive or negative. As a result, BPM’s time blips during those minutes normally lead or lag WWV and WWVH time ticks. BPM uses Chinese female voice identification during the last minute of each hour.


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