VOA Site B, Greenville, NC

I took a brief vacation last week along the coast of North Carolina. It was relaxing and fun to be sure. I was also aware of and slightly curious about the Voice Of America shortwave site, a slight distance inland in Grimesland, NC.  Thus, I made arrangements visit the facility on my way home.  Chief Engineer, Macon Dail, was gracious enough to give us the guided tour.  The facility is an engineering marvel.  The scale and complexity is enormous.  The entire facility is scrupulously maintained.  Many of the transmitters and other equipment have been upgraded to make them more functional.   I tried to take meaningful pictures, but in many cases, they simply do not to justice.

Edward R Murrow Transmitting Facility, (VOA Greenville Site B) Grimesland, North Carolina

Officially known as the Edward R Murrow Transmitting Station of the International Broadcasting Bureau, VOA Site B was constructed in 1961.  Six of the eight shortwave transmitters are original to the construction of the building.  The other two (BBC SK55 and AEG S4005) were added in 1986.  All of the dipole curtain arrays, rhombics, transmission line and the antenna switching matrix are also original.  A few brief statistics about this site:

  • Land area is 2,715 acres (1099 hectare).
  • Over twenty six miles (forty two kilometers) of 300 ohm open transmission line rated at 500 KW.
  • Sixteen dipole curtain arrays, average antenna gain 17 dBi.
  • Twenty rhombic antennas, antenna gain 15 dBi.
  • Two of the dipole curtain arrays can slew azimuth and take off angle.
  • Three Continental Electronics 420A 500 KW Doherty modulated transmitters.
  • Three General Electric 4BT250A1 250 KW high level plate modulated transmitters.
  • One Brown Boveri Company (BBC) SK55C3 500 KW PSM transmitter.
  • One AEG Telefunken S4005 500 KW PDM transmitter.
  • Antenna switch matrix connects any of the eight transmitters to any of the thirty six antennas

While we were there, both of the newer transmitters were on the air, running at 250 KW.  The GE transmitters are used as needed and the Continentals are rarely used due to age, difficulty to tune, change frequencies and gross power inefficiency.

The station staff has, out of necessity, fabricated some very cool upgrades to the transmitters and facility.  The first of which is the alarm annunciator, which is based on a Star Trek (Original Series) sound scheme.  Once or twice I heard the bridge general alarm go off, followed by a female voice stating the problem: “GB8, OFF AIR.”

Chief Engineer’s office.  NCC-1701; no bloody A, no bloody B, no bloody C, and no bloody D

The GE 250 KW transmitters have been retrofitted with a computer controlled auto tune system for frequency changes.  The antenna switch matrix controller has been replaced by a PLC based system.  As the transmitters are so old, many of the transmitter specific parts need to be machined or fabricated locally.  The rest of the transmitter parts are stocked in a large parts storage room, all of which is meticulously labeled and tracked.  The floors are waxed and spotless, there is no dust on the horizontal surfaces, the work shop is clean, tools are put away, grass and weeds are cut, etc.  All of these little details did not go unnoticed and indicate great pride by the staff in the facility itself.

The heart of the facility is the control room which consists of four rows of equipment racks and a central operating position elevated above floor level.  Arranged around that are the eight shortwave transmitters in two long transmitter galleries.

VOA Site B control room

From this point, the operator can view all of the transmitters in the two transmitter galleries.

Operating position

Around the control operator are arranged a series of computer monitors showing various station function status.

Transmitter modulation and status indicators
Antenna Matrix status and control
VOA transmitter control and status (center)
Audio monitoring router

The equipment is installed into the equipment racks by type; one rack contains the frequency generators for each transmitter, the next contains first stage power amplifiers, the next contains audio processors and modulation monitors, etc.

Equipment racks and Shift Supervisor’s  office
Transmitter frequency generators
Audio processors, modulation monitors and patch panels
Backup audio feeds

The audio comes from the VOA studios in Washington DC via satellite. There are Comrex Access links as a backup and the Gentner EFT-1000s are used as a backup to the backup.  Prior to 1995, an eight hop microwave system covering the 300 mile (483 KM) distance was used.

GE 4BT250A transmitter with computer controlled tuning system installed

The station staff has created a computer controlled tuning system for the GE transmitters. Each transmitter can change frequency several times a day, during each frequency change, all of the transmitter stages need to be retuned. When done by hand, this can take several minutes to accomplish. The computer system uses follow pots and micro controllers to set the tuning elements to specific values. They can be touched up by hand if needed. A frequency change can usually be done in less than one minute.

GE 4BT250A transmitter
Your humble author and CE Macon Dail discussing the auto tune system
GE 4BT250A auto tune modification
GE 4BT250A IPA tube and input tuning.

The 2nd IPA and PA input tuning work the same way. The copper sleeve slides up and down over the coil to change resonant frequency. The vapor cooled tube sits inside the tub at the top, anode facing down. These tuning sections are a mechanical nightmare according to Macon. One of the reasons why VOA site A was closed down was due to the frequent frequency changes at that site causing excessive wear and tear on the old GE transmitters. This particular transmitter was being repaired; the staff was rebuilding a tuning network bypass capacitor assembly

GE 4BT250A transformer vault

The GE transmitter transformers still contain PCB’s. The plate transformers are in the back, basically pole transformers, one for each phase. Primary voltages is 4,180 volts, secondary rectified voltages are 12 KVDC (PA plate supply)  and 15 KVDC (modulator plate supply).

Hallway and maintenance access to back of GE transmitters
AEG Telefunken S4005 500 KW transmitter on the air

While we were there, the newer transmitters were in operation transmitting Spanish language programming to the Cuba on 13,605 KHz and 11,930 KHz.  Currently, the Greenville site is broadcasting mostly Spanish language programming with some English, French and Bambara language programming for Africa.

A fact that does not escape the notice of the staff.

VOA transmitter gallery, showing transmitters GB8 through GB4
Continental Electronics 420A 500 KW Shortwave transmitter control and metering panel

The three Continental 420A transmitters (GB-1, GB-2 and GB-3) are essentially a pair of 250 KW amplifiers combined. As these are Doherty power amplifiers, frequency changes are very difficult to effect. These transmitters spend most of their time in backup service.

Electrical distribution panel

The antenna matrix building is very impressive. Routing eight 250 or 500 KW transmitters to 36 different antennas takes a bit of doing. Mechanizing that set up is no mean feat. The pictures I took of the antenna matrix building do not show the size and complexity of the system.

Transmission line between transmitter building and antenna matrix building

For that, we need a satellite photo:

VOA Site B antenna matrix building

Basically, the transmitter building is in the lower left hand side of the picture. The transmission line go over to the antenna matrix building (looks like rectangular duct work), then run all the way to the back of the building. Each antenna transmission line come into the building and runs to the other side. Pneumatic arms then couple the transmitter line to the antenna line. This is all controlled by a custom made PLC and controlled by the operator from the main operating desk.

Custom made antenna matrix control system
300 ohm open transmission lines
300 ohm open transmission lines

Some of these lines are very long but have low loss due to the air dielectric. The most used antennas are the dipole curtain arrays.

Dipole curtain arrays

These consist of a series of broadband dipole antennas arranged side by side and stacked three or four high. behind those antennas is a reflector screen. There are two curtain arrays that are slewable. The dipole antennas phase relationship to each other can be changed to adjust the take off angle and azimuth, thus giving optimum coverage to the targeted area.

Close up curtain array

In this picture, the dipole antennas are to the right. Behind them is the reflector screen, behind that is the antenna feed system. Each antenna feed goes through the reflector screen to the center of the dipole antenna.

Each array requires four towers to support it.

Curtain dipole array supporting towers
Curtain dipole array supporting towers
Remote Antenna Switch.  Allows two antennas to use one transmission line.

The entire antenna field is viewable from an observation platform on the main building

Observation room
Entrance gate and slewable curtains in background
Curtain arrays

The entire facility is very impressive. The truth is, I could have spent several more hours there, but I know that people have jobs to do and I felt that I had taken up enough time. We often forget in this country that not everyone in the world has access to the internet. Shortwave broadcasting has a long reach and is not subject to government controlled firewalls or other forms of electronic censorship. Currently, the Greenville site is broadcasting mostly Spanish language programming with some English language programming for Africa. There are many areas in the world that are in political tension right now, some startlingly close to home. Places like Brazil, Argentina and Venezuela have been in the news lately. I do not see a time when these long reach broadcasting services will not be needed. Becoming a welcome source of good information for those affected people is good for brand USA. It would be money well spent to invest in a couple of new Continental 419H (still made in the USA) DRM capable transmitters for this facility. While the old GE and Continental units are great, the time may come when they are really needed but unavailable due to being down for repair.

Special thanks to Macon Dail for his time, knowledge and patience.

Night of nights, 2015

Every year, the Maritime Radio Historical Society celebrates the closing of the last commercial Morse code radio station, which happened at 0001 UTC, July 13, 1999.  They do this by re-manning the watch for a few hours in honor of all those who so diligently listened for distress signals on 500 KHz and other frequencies continuously for over 90 years.  Your humble author was one of those, who in the late 1980’s and early 1990’s strained to hear, through the static crashes and OTHR, the simple, yet effective combination of SOS sent in Morse code.

Fortunately, after the closure of KPH, the National Parks Service took over the land and preserved the buildings and antenna fields intact.  Today, a dedicated group of volunteers maintain these facilities as a working museum.  This is the earliest history of radio technology and from this, sprang Amateur Radio, then Broadcast Radio services.

So, if you have the opportunity on July 12 (Sunday, starting at 8 pm, EDT), tune around to some of the frequencies listed below and see how ship to shore communications was handled:

KPH KFS KSM WLO KLB NMC NMW Ship transmit
426 426 488 472 448 425, 454, 468,480,512
500 500 500 500 500 500
2055.5
4247 4343 4184
6477.5 6383 6276
8642 8438.3 8658 8582.5 8574 8368
12808.5 12695.5 12993 12992 12552
17016.8 17026 16914 16968.5 17220.5 16736
22477 22280.5

These are duplex frequencies, meaning; the ship transmits on one frequency and listens on to the shore station on another and vice versa.

Those medium frequencies do not carry that far during daylight, however the high frequencies should be heard across the world.

In addition to that, there are youtube videos to watch:

There are more videos on youtube, if one is so inclined.

Those old RCA transmitter look like they are in excellent condition. Somebody has spent a lot of time restoring those units.

Hopefully, one of these years, I will get a chance to head out to San Fransisco during the middle of July and see this in person. It would be nice for my children to see what their old man used to do in what seems like a different lifetime.

Something fun

So, I spent wasted several hours on this SDR website over the holiday weekend:

University of Twente SDR website
University of Twente SDR website

This is a web based SDR hosted by the University of Twente in Enschede, Netherlands. I enjoyed listening to the European medium wave and shortwave stations available.  Something that is always fun to checkout: UVB-76 on 4625 KHz.

Have fun!

PS: A special thanks to all those who have donated to the cause via the donate button on the upper right side bar.  I had enough money to buy a FUNcube dongle SDR.  I think I have all the other necessary hardware to launch one of these sites myself.  If or when that happens, I will post a link here.