The usual procedure is to tune a jamming transmitter onto the same channel as the incoming and supposedly undesirable broadcasts, and then modulate the jamming transmitter with noise, or music or noisy programming. In this way, it becomes very difficult or even impossible for listeners in the target country to hear the programming from the distant radio station.
Back during the era of the Cold War, shortwave listeners all around the world were aware of multitudes of jamming transmissions that were heard all across every international shortwave band. This annoying procedure began around the year 1948.
However, it was on the evening of November 29, 1988, that the Soviet Union ceased to jam all foreign radio stations. Thus it was that the extensive jamming era that lasted for 40 years was now over. It is stated that when the USSR switched off their massive network of jamming stations, they were operating more than 1600 jamming transmitters in about 120 jamming radio centers.
However, two years later again, there was another running of the America’s Cup, the 12th since the original event in 1851, when the American yacht, “America” won the race around the Isle of Wight in the English Channel; hence the name, “America’s Cup”. In the 1903 event, the American yacht, “Reliance” owned by another financier Cornelius Vanderbilt was competing against the British “Shamrock 3”, owned still by Sir Thomas Lipton. During this event, there was at times some form of deliberate jamming apparently by a 3rd party.
The results of this 12th America’s Cup were that the American yacht “Reliance” won the three stages of the 1903 race, and neither AP nor PPA received any reliable news bulletins by wireless. This was the 1st known case of the deliberate and planned jamming of wireless transmissions, and it happened just 109 years ago, in the summer of the year 1903.
(AWR Wavescan/NWS 189 via Adrian Peterson)