J and D's Corner

Our Photo Attic - Stuff from Here & There

Some snapshots of the big VOA relay station that operated on Okinawa up to about 1977

In running through boxes of photos I came across a series of snapshots taken in 1968 during a tour of the VOA facility that then operated from a site near Okuma village in the north part of Okinawa.   Googling the web didn't produce much on the station so I figured why not post them for broadcasting/radio buffs, or whoever might be interested.

I was on Okinawa in the late '60s as an Air Force enlisted man, working as "transmitter & master control chief" at the AFRTS AM/FM/TV station located atop Rycom Plaza.  I boondoggled up to the VOA station one day and was much impressed by the quality & quantity of equipment they were running, hence the batch of photos.

They had several short-wave transmitters & associated antennas, but the crown jewel was a 1-million watt transmitter operating on 1174 kHz  in the AM broadcast band (I have seen other sources that list a slightly different frequency, but 1174 was what I noted down).  It was, I believe, a Continental 105B, one of several the VOA operated in various parts of the world at that time, and was used to beam programming into Communist China.  (Addendum 02/2011: I've had a couple of great emails providing some corrections & clarifications to my photo descriptions from Sheldon Daitch, who had worked the sister station to Okinawa located at Poro in the Philippines.  Any more input, or pictures, would be welcome from any source.)

Operating only after dark, when sky-wave propagation kicked in and the station could be heard in China, it had a 6-tower directional antenna, very tight pattern lobes apparently because in spite of the huge power output it was actually relatively weak when monitored down in the populated southern part of Okinawa.  Near the station, however, a few local pig farmers discovered they could take a plain fluorescent bulb, tie a couple of pieces of wire to the pins on the ends as "antennas", and hang it in their sheds as a free night-light powered by the RF from the big transmitter.  The Chinese, of course, jammed the station as best they could, but presumably it punched through well enough in many areas to be useful.

The transmitter station had an associated receiving station located some distance away which picked up & fed programming relayed from the USA.  They may have had at least limited use of telephone-grade undersea cable circuit(s), I don't recall specifically,  but in those days most program material that wasn't shipped out pre-recorded had to be linked in by short-wave radio.  Quality was generally fairly good, better than the telephone-grade circuits, but obviously not hi-fi by any means and was subject to static and occasional outages (see the sidebar story below).  Addendum:  According to a vintage VOA newsletter provided by Mr. Daitch, some of these HF program feed transmissions utilized Sterba curtain antennas with gains given as 20 dbi, a most impressive figure, fed by synchronized transmitters to produce effective radiated powers of some 200 megawatts, another impressive figure.

After Okinawa was legally reverted to Japanese control the VOA continued to operate from Okuma for a few years but for both domestic and international political reasons the Japanese didn't care for being in the position of hosting the site and I think Okuma finally "went dark" in 1977.  Today the Okuma vicinity, no longer way out in the "boonies', is a developed beach/resort area.

With the advent of satellites and the Internet things have changed a lot in international information distribution and international short-wave broadcasting is vastly less emphasized today.  In its heyday though it was a fascinating sub-culture.

Here are the photos from the trip (click on the thumbnail for full size):

VOA Receiving Station

Located south of Okuna, this facility received programming for VOA and, I believe, also did some support for FBIS (Foreign Broadcast Information Service), a group administered by the CIA

Interior of Receive Site

Racks of receivers were fed by an elaborate antenna/multicoupler system. They also had extensive audio processing capability.

Receive Site's Control Console

Today an operation like this would all be pretty much computer-automated but back in the '60s wet-ware computers (human operators) had to handle everything.

Tape Recording at the Receive Site

They had a whole array of Ampex tape recorders, which were hot stuff then!

Transmitter Site

This semi-panoramic view shows the main building and associated building which housed a shop and the power plant. They had a very pleasant, well kept little empire.

Another view Transmitter Site

This isthe generator building, which I didn't tour. The combined operation sucked up a LOT of AC power. Tank-like units on the side of the building are part of the heat exchange system.

Transmitter Control "Greenhouse"

From this control center the whole operation was run. The enclosure was needed for sound isolation, there were lots of motors, fans & pumps running.

Inside the "Greenhouse"

This was mostly audio control & routing, the actual transmitter monitoring was done from consoles outside the greenhouse.

Equipment Room

The site hosted several "conventional" HF transmitters, although my email guru Sheldon notes the one on the left is almost certainly not a Gates as noted on the photo. Shortwave antennas were, I think, mostly rhombics.

G.E. 100 kW Shortwave Transmitter

This transmitter represents the upper end of power for most short-wave broadcasting.

Final Amplifier tubes, 100kW Xmtr

The big 100kW shortwave transmitter was large enough to need water cooling. Distilled water, which doesn't conduct electricity, was run right through the coils & tube mounts.

The 'Big Gun', 1,000,000 watts

This Continental transmitter was actually composed of two 500 kW transmitters run in parallel, with signal originating in the oscillator of one of the two identical exciter/driver chains.

Trivia: At our SoCal Edison top-tier domestic rate of 31 cents/kwh, feeding this baby it's approximately 2.4MW of prime power would run about $731 per hour!

Another View of the Continental 1 megawatt

Continental made several of these, for VOA and others. They actually produced a few 2,000,000 watt units also. Probably those went to governments that just wanted bragging rights!

Control Console for the 1 MW

On a transmitter this size, you don't just hit the "on" button. Things had to be brought up with some finesse. All mechanical tuning was done by servos.

Rectifiers & Exciters for the Continental

Each half of the transmitter had its own RF chain but the basic signal originated from a single oscillator Modulation was at the driver level, the high-power stage was a linear-type amplifier.

Plate Transformers & Filter Caps

Looking like power company distribution equipment, these guys crank out over 2 million watts of high-voltage DC. As I recall, the plate voltage for the final amplifiers was very high, some 15,000 volts, with total plate current of about 160 amps. The tubes were Machlett ML-5682's, not something you could pick up at Radio Shack!

Water-Cooled RF Plumbing

The site had an extensive de-ionized water plant to supply cooling water, which circulated in closed systems through heat exchangers. I believe a sea-water exchange system ended up with the waste heat.

Power Switchgear

Again, it looked more like a power sub-station than an electronic system!

The site had its own multi-megawatt Diesel power plant, as the power requirements vastly exceeded what the local power & light could supply. Added trivia: When I was there a big chunk of Okinawa's power came from a "generator ship" floating in a harbor on the east side of the island.

Heat Exchangers

The closed distilled-water system gave up it's heat to what I believe was at the time a sea-water heat-exchange system, although I can't recall specifically any conversation about that aspect of it. I have been informed the Poro, Philippines sister station to this one was at some point converted to conventional plain-water cooling towers.

The Medium-Wave Antenna System

Somehow I got the impression this 6-tower array was actually two 3-tower arrays separately fed from the independent 500 kW power amplifier units via the two open-wire "coaxial" transmission lines shown here. However, I now understand it was almost certainly a combined single feed with the second transmission line being a spare.

For safety, no one could walk out to the antennas while the transmitter was on.

If you are interested in more detail on the big transmitter, you can download a full brochure by clicking HERE.

Sidebar Story:  The Joys of Short Wave Circuits:   Before satellites and broadband fiber optic undersea cables a huge amount of voice and data was transmitted across the oceans by short-wave radio, which worked pretty well much of the time but had its problems.

In the early-mid 1960's I was in Tripoli in North Africa where we received our news feeds via radio-teletype.  Signals were transmitted from Bound Brook, New Jersey to a relay station operated by Mackay Radio in Tangier, Morocco, which in turn re-transmitted to our area.   Worked fairly well although 24-hour coverage involved several changes of frequency and periods when poor signal resulted in a lot of garbled copy (as luck would have it just such a period coincided with the first reports of the Kennedy assassination, leading to considerable angst for the responsible tech {that be me}, but that's another story).   It was a daily occurrence at morning & evening to see copy gradually get worse & worse and finally become unusable on a given frequency, so we were quite attuned to that normal ebb and flow of things.

One day, though, at mid-day the teletype machines were chattering along producing perfect text at 60 wpm, a dum-dum-dum tempo which still echoes in my brain after all these years (in fact my typing was for years after locked at that 60 wpm max rate).  Suddenly, the room went quiet with the machines simultaneously suspended in mid-word.  After some minutes passed Mackay Radio started "call-banding" on all circuits, running a loop which repeatedly typed out their call and a 'please stand by', but still with perfect copy.  This was odd, and I started looking at different frequencies, starting with the New Jersey stations which we often could receive direct.  Nothing.  Ditto any of the shortwave broadcasters regularly receivable direct from the USA.  To top it off numerous European & Middle East VOA shortwave broadcast stations were playing the VOA's "Columbia, Gem of the Ocean"  music tag over and over instead of program material, the equivalent of Mackay Radio's call-banding and demonstrating a loss of their own incoming signals. 

What quickly became apparent was that, for all intents & purposes, the United States of America had suddenly gone "off the air" as far as short-wave transmissions were concerned.  Understand this was the era of the Cold War, with the possibility of nuclear attack always in the back of everyone's mind, so we were understandably a little on edge as we worked with the problem.

We were quite relieved to find, after some further coordination & analysis, that a powerful solar storm of exceptionally abrupt onset had essentially severed all trans-Atlantic shortwave paths literally in mid-word, but without immediately affecting the Europe-Mid East area.  By the next day or so life had drifted more or less back to normal and we had learned another lesson about the joys of depending on short wave circuits.

For more on whys & wherefores of the Tangier Morocco relay stations, click here for a nice write-up featuring the RCA station in Tangier.  The remains of the RCA installation were photographed in 2008 by Sheldon Daitch and are viewable here.