As a broadcast engineer and shortwave listener, I enjoy not only the efficiency of a shortwave signal propagating through the ionosphere and reaching more the earth than any other broadcast signal, but also the variations of space weather affecting a distant signal reaching my receiver.
While the Internet has replaced most countries’ shortwave efforts, a few domestic stations are soldiering on. WRMI is one of them, and is now enjoying a much larger presence with the old Family Radio WYFR facility, which they acquired in December 2013.
WRMI has an interesting history, as does WYFR. When owner Jeff White of WRMI took over the large transmitter site of WYFR, I contacted a few technical people involved and learned what it takes to run a power-hungry operation and learned some interesting war stories. Shortwave (“HF” to veterans) requires unique systems and maintenance as compared to FM and even AM facilities. To learn more I reached out to White; Dan Elyea, WYFR retired engineering manager; and Terry Elders, current facility manager.
Elyea had worked for Family Stations since 1973. An inactive ham, he kept detailed notes about the site and was most generous of his time and information. Elders has worked 28 years at WYFR. A modest person who operates the transmitters, he also maintains the systems supporting the transmitters, such as logic, power, the IP network and finally, all the antennas.
Located in rural Okeechobee, Fla., the WYFR site was completed in 1988 and is the largest private HF transmitter plant in North America, with a dozen 100 kilowatt transmitters and one 50 kW transmitter feeding some 23 various antennas aimed at the four corners of the earth.
WYFR started as an early experimental station, W1XAL, in Boston. It later moved to the seaside town of Scituate and became WRUL — for “World Radio University for the Listener” — an educational station that leased airtime to broadcast the Voice of America broadcasts during World War II, and later aired Armed Forces Radio in the 1950s and ’60s (Fig. 1).
The station was then sold a few times, and eventually the call letters were changed to WNYW, from which Family Radio leased air time in 1972. In 1973, Family Radio purchased the station. In 1976, Family Radio leased land in rural Florida, and in 1977, began transmitting from a single 100 kW transmitter in Okeechobee.
Once the new site was on the air with a single transmitter, the Scituate WYFR engineers transferred each of the five transmitters one at a time to Florida. The last transmitter was moved in 1979. This consolidated their HF operation. Over the years, they purchased more transmitters and even built some! They also built some of their own antennas.
BUILT IN THE TROPICS
Situated on 660 acres of rural pastureland 20 miles north of Lake Okeechobee in Florida, the location is semi-tropical with potent thunderstorms during the summer. In the center of the plot of land is the transmitter building, which houses the control gear, power distribution and climate control. The power feed arriving at the building is 23 kV (it was 11.8 kV early on), which is stepped down to 480 volts three-phase to feed all the transmitters.
A large central control room is in the building. There are computers to control the frequency synthesizers for channel selection of the various transmitters and some basic control of the transmitters as well as some antenna switching.
Each transmitter has a bay in the rows of racks located in the center of the Control Room (Fig. 2). Items for each include an attenuator for the program feed, a Belar modulation monitor, a PTS frequency synthesizer to generate the carrier for the transmitter, an antenna switch control box, a computer that attends to several automated functions for that transmitter and an Optimod audio processor.
Shortwave station transmitting frequencies and times are managed by the High Frequency Coordination Conference, under the watch of the International Telecommunications Union (www.hfcc.org). Any HF broadcast station can transmit on a number of shortwave bands, located in spots between 3 MHz and 30 MHz. With the HFCC’s worldwide coordination on a per-quarter basis, WRMI is on the air at 5015, 5850, 5950, 5985, 7455, 9955, 7570, 7730, 11825, 15190, 15770, 17790 , and 11730 kHz, 7 days per week. The best frequencies to tune into in the U.S. are probably 7570 and 9955 kHz. The WRMI schedule can be found on their website: www.wrmi.net.
Domestic HF stations are regulated by the FCC and must have a minimum power of 50 kW. The use of different frequencies along with directional antennas at different times allows a station to reach most parts of the populated world (Fig. 3). For WRMI, they can beam to 11 areas, but their main areas of interest are Latin America and the Caribbean. The new plant also can send a potent signal to Africa. In general, when the 11-year sunspot cycle is at its peak, higher frequencies such as the 19 MHz band can send a signal the farthest during the daytime; while when we are at a sunspot minimum, the 5 MHz band is the best during nighttime.
There are 13 transmitters at WRMI. The oldest is a now-retired Gates HF-50, a 50 kW plate modulated tube transmitter with a couple of sister HF100s. The newest is a Continental 418-D transmitter with solid-state modulator (Fig. 4).
Dan Elyea explains how they copied the Continental transmitter because the network’s technical director requested that the HF engineers build their own transmitters to save money: “At the time, I thought the concept to be impractical, and surmised that the ambitious plans involved a lack of knowledge of the complications of building transmitters that must cover the wide range of frequencies required for shortwave operations. I never expected that we actually would build our own shortwave transmitters, never mind eight of them.”
So they bought two Continental 418-D 100 kW transmitters, designed by George Woodard (Fig. 5). Continental gave them permission to copy their 418 transmitter as well as buy certain components. According to Dan, “We hired a young engineer, John Koch, to head up the transmitter construction project. John took a vast number of measurements on the existing Continental transmitters, carefully documenting all aspects. He determined the approach we would take on mechanical construction of the cabinets and such. For the most part, we followed the Continental electrical design.”
The last transmitter was built in the fall of 1988. They were able to build these transmitters for less than half the cost of commercially-built transmitters.
In later years, the tuning of the RF driver amplifiers was upgraded. They replaced the modulator driver and first RF stages with solid-state amplifiers. They also changed the IPA tuning from a single motor driven control to separate inductor and capacitor adjustments to allow for more repeatable settings.
According to Elyea, “This greatly smoothed out the tuning of that stage and we accepted the downside of the Q varying and an additional tuning drive. We implemented a system of semi-automated presets for all the tuned components. This reduced the load on the Operator at frequency change times, especially when there would be multiple transmitters changing frequency in the same time frame. The presets drove the tuning motors to the right setting for a given frequency, requiring only fine-tuning by the Operator after bringing up the high voltage.”
CURTAINS, LOGS AND RHOMBOIDS
The site has 23 antennas of five types. The TCI-515, 516 and 527 are log periodics (the 527 being a double-log), a TCI-611 dipole curtain antenna and older homemade double rhomboids (Figs. 6–8). The five styles represent the advances over the decades. Double rhomboids give a narrow main lobe, while log periodics are a newer design and provide wider frequency coverage. After buying a couple of log periodic antennas, the rest were manufactured onsite. They built most of their antennas. Elders recalls, “It would take a lot of man-hours. When TCI would send an antenna out, we would measure every item (angles and lengths) to the nth-degree. Once an antenna was fully documented, we built the others from these plans.”
Their short-range log periodics provide a smooth pattern and serve close-in areas such as Cuba, due to their high take-off angle. The other log periodics feed moderate distances such as Western North America to their lower take-off angles. The WYFR curtain antenna provides high gain for Europe. The older double rhomboids send signals for long and moderate distances to Europe, South America and Africa. They take up less space than a traditional rhombic and produce a pattern with multiple lobes.
Most all antennas can be switched between the transmitters, a couple of transmitters can feed one of three antennas, and a few transmitters are wired to a particular antenna. All of the antennas are fed by 300-ohm open wire balanced feed line to match the output of the older transmitters. The newer transmitters are 75-ohm coaxial output, so the station engineers use a Continental tuned balun located a distance away from the transmitters.
The antenna control was designed in-house. To move the switch contacts, the antenna switches have 120 VAC motors that are controlled by 24-volt DC relays. When an antenna switch reaches the requested position, another relay is fired as status back, closing the transmitter interlock. Other transmitters are then inhibited from routing to that antenna.
The operation of a high-power transmission facility has its own special concerns and the engineering staff has many stories of unusual events.
Sometimes a transmitter would sound a loud “bang!” when brought up after an antenna change, only for them to find a lizard or snake on the diode stacks. Occasionally, they would turn on a transmitter and it would simply arc over. They would attempt to turn it off, but it would continue to arc. Elders noted that high-voltage 12 kV feeds can go wherever they want. He also said seasonal changes require retuning, which can take time, especially when the neutralization requires adjustment. The older transmitters also needed to be retuned every half hour or so as the settings tended to drift.
These days, they can no longer get modulator and PA tubes for the Gates HF line of transmitters. The 6076 power tetrode driver tubes are also unavailable. The last tubes they bought were from an old de-commissioned ship. They have a fabricator on staff to build things as needed, and this expertise helped them immensely after the hurricanes. Some employees are ex-military, hams or weekend warriors.
At any transmitter site, the hazards of the natural world can be a challenge. With shortwave and its massive antennas, it can be especially difficult. In the hot Florida summer sun, humid air adds to the wounds caused by weather. The site has seen the wrath of three large hurricanes: Frances and Jeanne in the summer of 2004, and Wilma in 2005. For hurricane Francis, they shut down the plant and covered the transmitters and control room with sheet-plastic.
Jeanne hit soon after, and as usual, the power went out. The main roof peeled back in the winds and allowed a lot of rain to enter. It took the gang more than three weeks to get all the transmitters and antennas back on line. About a year later hurricane Wilma arrived. Their new roof held well, but there was some damage to the antennas, transmission line and switches.
As far as regular weather, the Southeast often has morning dew and high humidity. Elders said they did not have a problem with humidity when the transmitters were all running constantly. In recent years, when they had a sparse schedule and turned the transmitters off during the evenings, the moisture of the fog and dew in the morning would cause some of the switches to arc. Dust can also be a problem, and when the wind is coming in the right direction, or if farmers are burning off a field five miles away, the ash and dust will cause the transmission lines to arc (Fig. 9).
If that were not enough, Florida is known as the lightning capital of the United States. For the transmitter facility, their being situated in this high-risk area often provides for active times for the engineering team. They would often have power dropouts when the utility feeds would trip, and also often experience blown antenna switch control line fuses. They have also seen some shattered transmission line wood poles due to lightning (Fig. 10).
Elders adds, “Lightning will wreak havoc on us. I have seen a storm come by and light us up really good. When we are broadcasting, I have also seen storms come by us and dissipate as it passes over us, only to build back up as it goes down the road. Lightning burns up our antenna switches often. Sometimes, we would get repeated power outages due to storms, and resetting all 14 transmitters takes some time, just as the next lightning hit takes us off again. We have even seen lightning pass through the building. It gets wild out here.”
For such power losses and spikes, the control room has surge suppression, UPS and a 25 kW standby generator, which keeps up the terminal gear, but not the transmitters. The antenna switches also have surge suppression.
WRMI owner Jeff White is keeping on his staff many of the current engineers and technicians who know the site. They have installed new computers for audio delivery and have decommissioned the oldest Gates 50 kW transmitter. On Dec. 1, 2013, the site call sign changed to WRMI; the old WYFR call letters will be used by Family Stations for one of their AM or FM stations.
For me, shortwave is fun to listen to; but it takes much effort for an engineering team to keep an HF station on the air. This article was meant to illustrate the accomplishments of the WYFR engineering team, many that are unique to HF transmission. The engineering team performed difficult engineering feats over the years, such as building their own transmitters and antennas, and repairing them often under adverse conditions. With WRMI taking over the site, a radio David has taken over an RF Goliath and has renewed the enjoyment of shortwave for many listeners.
Many thanks to Jeff White of WRMI, Terry Elders and Dan Elyea of WYFR. These folks have given much time to me and provided many of the photos and graphics for this article.
Dan Brown is maintenance engineer for WGBH Educational Foundation in Boston.
Have a facility story to share? Email [email protected].