The origin of callsigns as an identification for radio stations goes right back into the era when distant communication was achieved via connected telegraph wires. Instead of spelling out a specific location in Morse Code it was easier and quicker to identify a specific location with just one or two or perhaps three letters and numbers. Thus, when distant communication was achieved by wireless, then the same system fell into use. Initially, any wireless station could choose any short combination of letters and numbers as a callsign and this would make identification quick and easy. Simple as this may seem, yet the usage of radio callsigns has in itself become quite a cumbersome issue.
For example, a radio callsign can be used to identify a specific transmitter.
As an example, the callsign KWID identified a 100 kW transmitter located at Islais Creek near San Francisco in California during the era of World War 2. When this transmitter was on the air, it was always identified as KWID, regardless of the frequency in use. However, back during that same era, the BBC in London issued a separate callsign for each different shortwave frequency, regardless of the actual transmitter or location. Thus callsign GRC identified a 50 kW transmitter on the frequency 2880 kHz, and GRB identified a 50 kW transmitter on 6010 kHz.
However, during that same era, Radio Australia followed a slightly different pattern again. Each basic three letter callsign identified a specific transmitter, such as VLC at Shepparton in Victoria and a suffix number indicated a specific frequency. For example VLC2 identified the 50 kW RCA transmitter at Shepparton on the frequency 9680 kHz, and VLC3 identified the same transmitter on another frequency 11870 kHz.However, due to many changes in frequency over a period of many years, this system became somewhat cumbersome, and so they subsequently adjusted the numeric suffix to identify a particular MHz band. For example VLA9 would identify a 100 kW transmitter VLA at Shepparton on any frequency in the 9 MHz band (31 metre) and likewise VLA15 would identify the same 100 kW transmitter on any frequency in the 15 MHz band (19 metre).
Another usage of a callsign became evident in the United States during the war in the middle of last century. A specific communication transmitter that was licensed under its own callsign was granted another callsign for a particular program service. The large communication station operated by PWI Press Wireless International at Hicksville on Long Island New York operated many shortwave transmitters, and even some of the staff who worked there did not know how many. These transmitters ranged in power from 10 kW up to 40 kW and 100 kW. Beginning in April 1942, PWI Hicksville began the relay of VOA Voice of America programming beamed to Africa and Europe.
However one year later, beginning in March 1943, PWI Hicksville began to identify their on air programming with four letter callsigns such as WKRD WKRX and WKLJ for which some QSLs were issued. These callsigns did not identify a specific transmitter nor a specific shortwave channel, but rather a particular program service. Over a period of nearly two years, a total of at least a dozen four letter callsigns were applied to the program relays over these PWI communication transmitters, a procedure that ended in February 1945. The PWI usage of the four letter broadcast callsigns still defies interpretation and understanding even to this day.
Medium wave radio callsigns in the United States seem to indicate, one call, one station, regardless of the number of actual transmitters they may operate. However, in earlier years the one transmitter could be licensed with more than one callsign. For example, back in the year 1934, the university radio station in West Lafayette Indiana operated a facility with three different callsigns. For program broadcasting, the callsign was WBAA; for experimental radio transmissions, the callsign was W9XG; and for amateur communications, the callsign was W9YB.
At one stage the ABC shortwave station located at Lyndhurst in Victoria Australia operated a total of ten shortwave transmitters, each rated at 10 kW. All of these transmitters were used in consecutive rotation for all of the broadcasts of all of the program services.
The callsign VLH was originally a single transmitter callsign and it usually carried a relay of programming from 3AR Melbourne. However as time went by, the call VLH became in reality a program service from the ABC studios in Melbourne.
In 1987 for example, there was a daily overlapping period of ¾ hour in which there were two transmitters on the air under the one callsign VLH:-
0830 - 0915 UTC VLH9 9680 kHz & VLH15 15230 kHz
In a different setting, sometimes callsigns were varied according to the location to which the transmissions were beamed. For example, back in the mid 1930s, transmitters VLK VLM and VK2ME at the AWA station at Pennant Hills near Sydney in Australia were used at times for international radio communication. When beamed to England, the callsign was VLK; when beamed to Indonesia, the callsign was VLJ (Java); and when beamed to New Zealand, the callsign was VLZ.
However for program broadcasting at the beginning of World War II in 1939, the callsign was VLQ.
So how then should we understand the usage and application of international radio callsigns? There is only one answer. We should understand and interpret the usage of radio station callsigns according to the actual usage by the station itself whose story we are studying.
(AWR Wavescan 465)