Visit to Wooferton Transmitting Station
On Saturday 7th September, a group of Gloucester Amateur Radio and Electronic Society members joined a visit to the Wooferton transmitting station.
Operating on various shortwave bands, the station broacasts BBC World Service, Voice of America and Deutche Welle programmes to North and South America, Europe, Asia and Africa.
Our visit started with a tour of the Antennas, which included masts up to 300 ft (90m) tall supporting curtains of folded dipole antennas. One interesting aspect of these antennas was their ability to use multiple arrays with changable phasing loops to change the direction of the transmitting lobe by up to plus or minus 20 degrees.
The antennas are fed using 328 ohm open wire feeders with switching stations that allow each transmitter to be switched to a multitude of antennas.
Folowing our trip around the antennas, we visited the transmitter hall. The transmitters varied in age from the 1960's to the present day with powers from 50 to 350 killowatts (KW).
All of the transmitters broadcast AM (Amplitude Modulation). The earlier transmitters use a conventional design of modulating the final radio frequency (RF) stage. This is very inefficient and we were shown a 350 KW transmitter that needed 180 KW of audio to modulate it. It used a modulation transformer that was over 5 foot (1.5m) on each side and an RF choke well over 6 foot (2m) on each side. Ufortunately, these were housed in a room that was much too small to take a photograph.
The modern transmitters use Amplitude Modulation Companded (AMC) to digitally modulate the RF signal. Not only does this more than double the efficiency, it allows for better low signal reception with a lower transmitted power.
Many of use were struck by the size of the components used.
Finally, we visited the control room where programmes schedules are automatically executed. We were given a demonstration of a test transmission and their ability to monitor its reception in various countries.
The station also rebroadcasts television to overseas countries where it id rebroadcast or incorporated into programms by local television companies.
We also have photos from...