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"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, September 20, 2009
Daventry Calling - 2: Station G5SW Chelmsford
In the progressive development of events that brought about the establishment of the famous BBC shortwave station located at Daventry in the Midlands of England, we take up the story of the early shortwave station that was licensed as G5SW. This transmitter was inaugurated at the Marconi factory in Chelmsford, it was subsequently moved to Daventry, and it remained in service for a magnificent total of 32 years. This is the story.
Back in the year 1898, the young Marconi, just 24 years old, established a wireless factory on Hall Street in Chelmsford, England, some 35 miles north east of London. This venture was so successful that he constructed his own factory building on New Street in the same town 14 years later and transferred the manufacturing of wireless equipment into it in June 1912.
In 1919, Marconi constructed a 6.5 kW experimental broadcast transmitter, the power of which was increased to 15 kW during the following year. With the usage of this transmitter, Marconi began the broadcast of a regular news service that was radiated on 107 kHz, which of course is a channel in what we now know as the standard Longwave Broadcast Band.
Soon afterwards, a very famous radio broadcast was made from this transmitter when the Australian opera singer, Dame Nellie Melba, made a scheduled broadcast that was advertised in advance in the newspapers. This broadcast, on June 14, 1920, was heard widely throughout islandic Europe as well as over in continental Europe and beyond, and it is looked upon as being a significant milestone in the development of radio broadcasting, not only in England, but around the world.
Shortly afterwards, Marconi launched a regular broadcasting service for the benefit of Londoners over the famous original station 2LO in London. This station was subsequently taken over by the BBC.
Now, around this era, the usage of shortwave transmissions for international communication as well as for program broadcasting was already proving to be a successful procedure. Marconi himself had performed several successful long range tests, and experimental shortwave broadcasting was already on the air from shortwave stations in the United States and Australia, as well as in England itself.
With these facts in mind, Marconi constructed a 10 kW shortwave transmitter in the year 1927, and the first broadcast transmission from this new unit took place on Armistice Day 1927. This inaugural broadcast on November 11 commemorated the end of what we now call World War I, and the programming was shaped to honor this occasion.
This new shortwave transmitter was hurriedly assembled from already available equipment and the two aerial masts, 475 ft. high, supported an aerial that was omni-directional and vertically polarized. The original channel was around 12.5 MHz, though this was changed in the following year to 11750 kHz in accordance with the new international regulations enacted at the recent Washington Radio Convention.
Thus began a regular international radio broadcasting service that was heard around the world, and reported quite frequently in radio magazines published in England, the United States, Australia and New Zealand. Programming for this shortwave broadcasting service was usually a relay from the local station 2LO and these transmissions were on the air in this way for a little over three years.
These international broadcasts were so successful that the BBC made arrangements with Marconi to rent the shortwave transmitter at Chelmsford as a preliminary program service while their own large station at Daventry was under construction. The BBC took over the programming for shortwave G5SW in 1931, and on January 5 in the next year, that is, 1932, the BBC introduced their new extended Empire Service.
Later in the same year, the BBC began test broadcasts from their two new 10 kW STC transmitters at Daventry. Interestingly, these Daventry test broadcasts were on the air under the Chelmsford callsign G5SW, and we should remember that at this stage the Marconi transmitter G5SW was still located at Chelmsford, not at Daventry 100 miles distant.
Anyway, this five year old shortwave transmitter that was rented by the BBC was closed down on December 17, 1932 in favor of the two new transmitters located at Daventry.
However, two years later, in 1934, this now largely idle transmitter was re-activated for a very special occasion. His Majesty, King George V, was making a Christmas Broadcast to the Empire, a historic first, and the BBC made special arrangements to ensure that the broadcast was heard well at all points around the globe. The two new transmitters at Daventry carried this royal broadcast, and the Marconi transmitter at Chelmsford was re-activated for this occasion. However this time, it was on the air, not under its own callsign G5SW, but rather under a new BBC callsign, GSD. The same previous channel was in use, the old and well established 11750 kHz.
This special broadcast for Christmas 1934 by King George V was considered to be such an important radio occasion that it was relayed to the world also from the relatively new communication station located at Rugby, rather nearby to Daventry.
Early in the New Year 1935, transmitter G5SW was re-furbished, upgraded to 20 kW, modified to operate on several different shortwave bands, transferred to Daventry, and installed in an available open space in what was known as the 5GB Mediumwave Building. At this new BBC location, the historic Marconi transmitter was designated as Sender 3 and it was brought into regular broadcast service on May 19, 1935. Callsigns in use over this transmitter now depended on what frequency was in use, a new callsign for each channel in use.
Two years after its removal from Chelmsford and its installation at Daventry, this same transmitter was upgraded again, this time with a power output of 60 kW. During the intense events in the year 1940, Sender 3 was used for carrying the Forces Program on 6150 kHz.
However, as time went by, this historic transmitter became increasingly undependable, and ultimately, it was dropped from service, and it was finally removed from the 5GB Building in 1959. We would presume that it was simply, and unceremoniously, scrapped.