During our weekly Sunday night VHF net, a question arose about the National Institute of Standards and Technology’s (NIST) time and frequency station, WWV. Net Control asked, “When did WWV move to Colorado?” While a few of us could answer, it became clear that many of the newer hams didn’t know much about the WWV station.

Myself, being a ham from Boulder, Colorado and now living in Nashua, New Hampshire, I saw this as a great opportunity to share information I’ve gathered over the years, both about WWV’s operations in Fort Collins, Colorado, and its move from Maryland in 1966.

WWV is considered one of the oldest continuously operating radio stations in the United States. It was first established in 1919 by the National Bureau of Standards (now NIST) and originally broadcasted from Washington, D.C. Its primary purpose has always been to transmit accurate time and frequency signals, which it continues to do today from its Fort Collins, Colorado facility. WWV’s long history of broadcasting time signals makes it a significant part of radio history in the U.S.

Boulder, Colorado, is home to the NIST (formerly the National Bureau of Standards, or NBS) Atomic Clock, which serves as the time and frequency standard for the United States and many other countries around the world. I’ve had the opportunity to view the Atomic Clock “in person” at the NIST Laboratory.

The NIST atomic clocks use cesium atoms to keep incredibly precise time. Here’s a simplified explanation of the process:

1. Cesium Atoms: The atomic clock relies on the natural oscillation of cesium atoms. Cesium atoms absorb and release energy at a very consistent frequency when they transition between two energy levels.
2. Microwave Frequency: The clock generates microwaves that are tuned to match the exact frequency of the cesium atoms’ oscillation. The frequency at which cesium atoms oscillate is exactly 9,192,631,770 cycles per second.
3. Tuning to Maximize Accuracy: The atomic clock continuously adjusts the microwave frequency to ensure it matches the cesium atom’s resonance as precisely as possible.
4. Counting Seconds: By counting these highly accurate oscillations, the clock measures time. One second is defined as exactly 9,192,631,770 oscillations of the cesium atom.
5. Disseminating the Time: NIST broadcasts the official time using radio signals (via stations like WWV), the internet (through NIST’s network time protocol, or NTP), and satellite systems. These signals help synchronize clocks around the world.

NIST’s time standard is crucial for GPS systems, telecommunications, scientific research, and other industries that require precise timekeeping.

In 2013, when I was serving as the ARRL Colorado Section Manager, we hosted the Rocky Mountain Division Convention (Hamcon Colorado) in Estes Park, Colorado. Given its proximity to the WWV radio complex in Fort Collins, our committee thought it would be a great opportunity to arrange a tour for interested hams. Since WWV is a secure government facility, we needed special permission. The WWV Chief Engineer, who was also a ham, informed us that they had never conducted a tour before and it might be impossible, but he would ask. To our surprise, permission was granted with some necessary security measures in place. Interest in the tour was high, and we chartered a school bus to take a large group of hams to the facility.

The engineers at WWV went above and beyond, providing a comprehensive tour of the facility that included fascinating historical devices. We were able to visit the antenna sites and transmitters, with detailed explanations of their operations.

Historically, amateur radio operators played a key role in the technical development of the atomic clock and the WWV radio stations from their earliest days. Given that the atomic clock is housed in Boulder, CO, many members of the Boulder Amateur Radio Club (BARC) were among those who contributed to its development and advised on the WWV operations over the years.

ne of the more notable BARC members was Yardley Beers, WØJF (formerly WØEXS and W3 AWH), who earned his MS in Nuclear Physics in 1937 and a Ph.D. in 1941 from Princeton University, where Einstein was in residence at the time. Beers was a pioneering scientist who first utilized cesium as the core of the aforementioned time standard oscillator. He was a dear friend whose boundless curiosity, humor, and deep expertise in all things radio-related made him a wealth of knowledge for our club.

At 0000 GMT on December 1, 1966, the veteran time and frequency station WWV in Greenbelt, Maryland, shut down permanently. Almost simultaneously, a new station with the same call letters and services began broadcasting from Fort Collins, Colorado. The decision to construct the new station and relocate was driven by several factors, primarily the obsolescence of the old facility and significant maintenance challenges.

In contrast, the new station utilizes the latest transmitter designs, offering significantly more efficient operation. The setup also provides greater flexibility, as the transmitters consist of identical units—except for some higher-powered transmitters, which include an additional amplifier stage—that can be tuned to any frequency. At the old station, only a few of the eight transmitters were identical. Unlike the old transmitters, the new ones apply modulation at low levels, with all subsequent stages maintaining precise linearity. This allows for a wide range of modulation options, including AM or single sideband, with either sideband and any desired degree of carrier suppression. These features mirror those found in modern amateur radio transmitters.

Lastly, the move brings the benefit of administrative efficiency. WWV is now co-located with two other NBS standard frequency and time stations, WWVB (60 kHz) and WWVL (20 kHz), at the same site. Additionally, it is more convenient to synchronize the station with the NIST atomic standards, which are based in nearby Boulder, Colorado.

WWVH began operation on November 22, 1948, at Kihei on the island of Maui, in the then

territory of Hawaii (Hawaii was not granted statehood until 1959). The original station

broadcasts a low-power signal on 5, 10, and 15 MHz. As it does today, the program schedule

of WWVH closely follows the format of WWV. However, voice announcements of time

weren’t added to the WWVH broadcast until July 1964. In July 1971, the station moved to its current location, a 30-acre (12-hectare) site near Kekaha on the Island of Kauai, Hawaii.

Today, the methods for calibrating frequency, synchronizing time, and assessing propagation have evolved significantly due to advances in technology, though some traditional methods (like using WWV) are still in use. Here’s a comparison of how these tasks were done in the past versus how they are typically done today:

1. Frequency Calibration

Before (Using WWV and Manual Tools):

• WWV Broadcast: Operators tuned their radios to the exact frequencies broadcast by WWV (e.g., 5, 10, or 15 MHz) to verify or adjust their frequency dials
• .Signal Comparison: Operators might use frequency counters or calibrate their equipment using signal generators. By manually adjusting their radio to match the WWV signal, they ensured their equipment was tuned correctly.
• Crystal Oscillators: Some radios used quartz crystal oscillators that needed periodic manual adjustments to maintain frequency stability.

Today (Using GPS, Software, and SDRs):

• GPS Disciplined Oscillators (GPSDO): Modern radio equipment can be calibrated with GPS, which provides ultra-precise time and frequency data directly from satellites. GPSDOs lock the radio’s oscillator to the exact frequency provided by GPS signals.
• Software-Defined Radios (SDRs): SDRs can automatically lock to known reference frequencies or signals, often bypassing the need for manual calibration.
• Digital Frequency Counters: High-precision digital frequency counters, often built into modern equipment, can accurately verify a station’s frequency without the need for an external signal like WWV.

2. Time Synchronization

Before (Using WWV or Manual Clocks):

• WWV Time Signals: Operators would listen to WWV’s hourly time announcements and manually synchronize their clocks to the audio ticks or the minute mark. This ensured they had the correct Coordinated Universal Time (UTC) for logging contacts.
• Mechanical or Quartz Clocks: Station clocks were either mechanical or quartz-based, requiring manual adjustments for drift.

Today (Using NTP and GPS):

• Network Time Protocol (NTP): Computers, logging software, and transceivers are often synced to the Internet time servers using NTP, which automatically keeps time to within milliseconds of UTC. Many hams now use computers with built-in NTP syncing for contest logging and communication accuracy.
• GPS Time: GPS provides highly accurate time synchronization. Many modern radios or station computers are connected to GPS receivers that provide time directly to within a fraction of a second of UTC.
• Atomic Clocks: Although not widespread in amateur radio, some operators use atomic clock-based devices for extreme precision in timekeeping, often integrated with GPS.

3. Propagation Monitoring

Before (Using WWV and Beacons):

• WWV Propagation Monitoring: Hams listened to WWV signals on different frequencies (2.5, 5, 10, 15, and 20 MHz). The strength of the signal provided a rough estimate of how well certain bands were propagating, helping operators decide which frequencies to use.
• Beacon Stations: Operators tuned to beacon stations operating on different frequencies around the world. By monitoring when these signals were heard, they could get a sense of global propagation conditions.
• Sunspot Numbers: Many hams used published sunspot data and predictions to estimate the effectiveness of different HF bands.

Today (Using Online Tools and Real-Time Data):

• Real-Time Propagation Maps: Websites and apps like PSKReporter, DXMAPS, Reverse Beacon Network (RBN), and WSPRnet provide real-time data on where signals are being received and which bands are open. These platforms track signal reports and provide a visual display of current propagation conditions.
• Solar and Geomagnetic Data: Many hams now use online services that provide real-time solar flux, geomagnetic indices, and space weather data. Websites like Space Weather Prediction Center (SWPC) offer detailed insights into how solar activity is affecting the ionosphere.
• Cluster Networks: DX cluster networks provide real-time information on stations spotted around the world, giving hams direct feedback on current band conditions.
• Software Tools: Advanced propagation software like VOACAP or HamCAP allows operators to model HF propagation based on real-time data, including solar activity, time of day, and location.

Summary of Key Differences:

While older methods like WWV are still valuable, modern technology has automated and refined many of these tasks, making it easier and more precise for amateur radio operators to ensure their equipment is accurate and their communication effective.

NISTTime and Frequency Services