|
|
"Wavescan" is a weekly program for long distance radio hobbyists produced by Dr. Adrian M. Peterson, Coordinator of International Relations for Adventist World Radio. AWR carries the program over many of its stations (including shortwave). Adrian Peterson is a highly regarded DXer and radio historian, and often includes features on radio history in his program. We are reproducing those features below, with Dr. Peterson's permission and assistance.
Wavescan N685, April 10, 2022
The Voice of America on Mediumwave at Poro in the Philippines
The third relay station for VOA, the Voice of America in the Philippines, was located at Poro Point, 150 miles north of the national capital, Manila. Interestingly, though, that one VOA relay station at Poro was in reality four different radio broadcasting stations, all clustered together. We go back to the beginning.
The Wallace Air Force Base at Poro Point on Luzon Island in the Philippines was originally acquired by the United States for use as a Cavalry Base back in the year 1903. It was subsequently taken over for use as an American Air Force Base.
During the year 1950, at the time when China was supporting the North Korean attempt to take over the entire Korean peninsula, the Poro location was in use as a radio listening base for monitoring Chinese and North Korean broadcasts. Tents and other temporary housing was hurriedly erected, and sophisticated electronic equipment was installed.
In an attempt to cover the same Far Eastern areas with their radio programming, VOA announced its plan to install a massive one million watt mediumwave transmitter at that same Poro Point location. The radio behemoth they chose was an American made Continental transmitter Model 105B. It was in fact two 500 kW transmitters, combined in parallel to make a single transmitter in the one huge metal shell.
The first 1,000 kW Continental Model 105B was built for VOA as a longwave transmitter on 173 kHz, and it was installed in Munich-Erching in Germany in 1953. The intended coverage area from this super powered longwave transmitter was Eastern Europe, and in particular Russia.
Later in the same year, in June (1953), the huge one megawatt mediumwave transmitter, which like the longwave transmitter was manufactured in Dallas, Texas, was inaugurated at Poro in the Philippines with a single tall transmission tower. It is probable that this transmitter was the first one megawatt mediumwave transmitter Model 105B constructed by Continental.
The signal from that one megawatt unit on 1140 kHz was heard far and wide, loud and clear. The transmitter was accorded a Philippine callsign, DWVA, though that designation was never used by VOA, not in their on air announcements and not in their publications. The callsign DWVA indicates the following information:
In 1978, new international radio regulations required 9 kHz channel spacing in Asia, and accordingly the operating frequency for VOA DWVA at Poro in the Philippines was changed from 1140 kHz to 1143 kHz.
During the year 1995, a new one megawatt mediumwave transmitter was constructed at the Harris radio factory in Quincy, Illinois in the United States in preparation for installation at Poro in the Philippines. At 5 pm on Monday, June 26, 1995, this new one megawatt Harris mediumwave transmitter was activated at the factory in Quincy on 1143 kHz for a series of preliminary test transmissions.
That new Harris transmitter was their first one megawatt mediumwave transmitter, and later in that same year 1995 it was duly installed at Poro in the Philippines, most likely in the shortwave transmitter building. At that stage, the original Continental was taken into active retirement, as a backup if necessary for the newer Harris transmitter.
However, there was one major problem. The mediumwave frequency for VOA Poro 1143 kHz now suffered from severe interference in the Far East due to a Taiwan transmitter on the same channel, 1143 kHz, with a power of 100 kW.
Beginning on December 6, 1997, a series of test transmissions lasting nine days was conducted at Poro on what was considered a more successful mediumwave frequency, 1170 kHz. These test broadcasts, which were on the air via the Harris transmitter at VOA Poro in the Philippines, simply used instrumental music, rather than the regular VOA programming feed.
Nevertheless, VOA Poro still remained on 1143 kHz, though a new four tower directional antenna system was installed in an endeavor to propagate a stronger directional signal into the Far East. Then again, another series of similar weekly test transmissions was conducted six years later (2003), with both superpower mediumwave transmitters on the air simultaneously, the Continental on 1143 kHz and the Harris on 1170 kHz.
In 2005, the Harris transmitter was removed from its first location (in the shortwave transmitter building?) and reinstalled into a new and specifically constructed building, where it began operation at the full power of almost one million watts on the new and now regular channel, 1170 kHz. At that stage, the Continental was finally retired forever, after a half a century of lifetime service. It was both the first and the last Continental one megawatt to remain in active service.
However, the lifetime for the newer Harris super power transmitter was also coming to an end. In March 2013, VOA DWVA was noted in Asia and the Pacific as off the air, silent. The issues of the WRTVHB for the next few years showed the station as inactive, and then in the 2016 issue, it was no longer listed.
VOA superpower mediumwave at the Wallace Air Force Base on Poro Point in the Philippines was now totally silent, off the air and gone forever. So whatever happened to those two super power one megawatt mediumwave transmitters? We would guess that they were simply sold off locally as scrap metal.
You can see what remains of the VOA station at Poro on Google Maps. The two mediumwave station buildings and sets of antenna systems are still visible, in what appears to be a double overlay rendering dated in 1985, as well as more recently.
We will present the story of the shortwave station at Poro Point in a coming edition of Wavescan.