The Background : On the 19th August 1989, Radio Carolines BTA50H Ampliphase fifty transmitter was put out of action by the combined efforts of a boarding party of British and Dutch government officials.
During the 10 hour siege almost all of the removable internal parts of the transmitter were taken away, and some parts which were too large or heavy to easily move were severely damaged in
an attempt to stop it ever being used again. At that time, and for many years afterwards it was said by many that it would never work again. Following legal action in Holland, most of the parts
were returned to the ship in 1993, however some were damaged beyond repair, whilst other parts were missing. At that time there was no motivation or purpose to attempt to rebuild the transmitter, and the parts simply
laid in various crates and boxes, neglected and ignored. As the years passsed, bits were further damaged due to bad storage whilst others were being taken by over-enthusiastic souvenir hunters. (if you are one of those
persons, and have parts of the transmitter, please contact me, as an amnesty may be in the offering!)
The restoration project has its origins in early Summer 1999, shortly before the ship moved to Southend for the summer season. Following a discussion among a few technical members of the crew about the pro's and con's of various RSL transmitters and the uniqueness of the Ampliphase the conversation turned to whether it would be possible to build a modern solid state ampliphase transmitter. Discussion then turned to the fact nobody had considered rebuilding and preserving the fifty, or even surveying its general condition let alone if it's low power stages could be used for an RSL transmitter. It just lay there in the hold, a set of vandalised and almost empty cabinets, and a stack of crates and boxes in what had been the high voltage cage. Keen eyed visitors to the ship in Southend that summer may have been surprised to see things happening down below, as the cabinets were cleaned, and many of the major large parts were placed back into their rightful homes. Progress was slow, not helped by the missing handbook, but with a bit of web surfing, lots of information on Ampliphases slowly started to become available. Finally, in October that year, the handbook was located and plans could be made.
One of the moduator shelves was taken off the ship in early January 2000, and on the 22nd of that month, it was powered up, on my dining room table. See here for more information from that momentous day. It is a credit to the original build quality, that after 12 years of non-use, an undignified journey to Holland and back and storage in cold, damp, salt air atmosphere that it powered up and starting working immediately, with no bangs, flashes or smoke. Within a few hours of power being applied, it was producing a rather weak and distorted signal, but every great journey starts with a small step. Listen to Rob Ashard stumble through a dedication that evening (spot the subtle date/time reference), fed live from the satellite, through the modulator and recorded off-air on a radio-cassette just a few feet away. Meanwhile, during the early months of 2000, onboard the ship, cabinets were being cleaned out, parts identified, and reassembly work progressed.
Easter Sunday 2000 was a milestone in the restoration work of the previous 6 months when the newly refurbished modulator was re-installed into the trasnmitter cabinets. Many painstaking hours had been spent during the winter and spring lavishing a little TLC on the transimtter and individual components, testing, re-wiring and fixing the damage of 11 years earlier. The high voltage circuits were disconnected and isolated and confidence was high that nothing would go bang. Even so, it took a long slow breath and a moments reflection to turn the power switch. The lights dimmed and the Perkins generator coughed as the three blower motors roared into life together for the first time since 1989. Each motor had been individually tested - but this was something else. Relays clattered and clicked for a few seconds, but soon settled down. When it was obvious that things were behaving as expected, the filaments switch was operated, and a few seconds later we had glowing valves in the modulator and first stage drivers.
It was the following weekend before the Modulator outputs were reconnected to the driver grids and bias applied. After a quick tweak on the tuned circuits, we had grid current. A low voltage supply (approx 150 volts)was applied to the anode circuits and lo and behold cathode current started to flow. With the following stages removed, there was no load for the anode but it was still possible to watch the cathode current rise and fall as the anode tuning was adjusted. Click to enlarge the right hand picture below and just look at those meters!
Some of the most major damage to the trasnmitter occured in the high power combiner and filter network. Just about every item in these cabinets had been removed. As very few items like the coils are identified with part numbers, it was a mammoth jigsaw puzzle task trying to locate all the parts and reconnect everything. However, just a days labour and the empty cabinets were turned back into a filter unit, and almost all of the original parts have been relocated.
Before and After - The Filter-Combiner unit.
And that's where we leave it for now folks. Keep watching this space for more updates.
The Five and Ten transmitters
The Theory Page
Carolines Modulation curves
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