Radio jamming in Korea
Introduction
Korea is the only nation which has been divided into two states: South and North Korea (i.e. Republic of Korea and Democratic People's Republic of Korea). The two states have been hostile to each other since the Korean War in 1950. Because of the hostile relations, they began to jam radio broadcasts of its counterparts. Radio jamming on the Korean penisula make the border regions world's busy places of radio signals. MW jamming is dominet in the Korean Metropolitan area including Seoul and the DMZ (border between South and North Korea).
Radio Jamming in South Korea
The South Korean government is always jamming most of North Korean radio broadcasts on medium-wave. According to National Security Law in South Korea, it is illegal to mention frequencies of North Korean broadcasts (That is why the author, living in Korea, cannot mention those frequencies). If you are in the Korean Metropolitan area (Seoul, Incheon, and Gyeonggi Province) and the near-DMZ areas and if you tune in MW radio, you may hear strange signals on particular frequencies, mixing with North Korean radio broadcasts. The South Korean government has introduced several bizzare jamming sounds to prevent their citizens to receive radio broadcasts from the North; the sounds are sometimes annually changed. Some people criticise that medium-wave jamming by the South is quite weak to block the North Korean broadcasts effectively (the jamming transmission power seems to be between 20 to 50 kilowatts, while the targeted North Korean transmissions are of much higher transmission power -- over 500 kilowatts). On shortwave, jamming is relatively low; only a very few North Korean frequencies are slightly jammed. FM jamming is also carried out, but it is not quite recognisable than on medium-wave.
Television jamming in South Korea had been done before the introduction of Digital Multimedia Broadcasting (i.e. DMB). In Seoul, you could see colour bars on particular channels of the VHF Band III. Now, jamming on those channels is not carried out, but the channels are used for DMB broadcasting, which provides reliable portable digital television [multimedia] broadcasts.
Radio Jamming in North Korea
North Korea does not jam any South Korean commerical television and radio broadcasts, but jams some of the South Korea's state-owned radio and television broadcasts. Before the closure of South Korean shortwave domestic radio broadcasts (which is often targeted to the North) as of early 2007, 3930 kHz of KBS Radio 1, 6015 and 6135 kHz of KBS Radio Social Education had been severely jammed by the North. The type of the jamming was 'Jet Plane Noise', which made it much harder to hear the radio broadcasts. The North also jams the South Korea's clandestine shortwave broadcast, Voice of Hope (which seems to be produced by South Korea's National Intelligence Service). Futhermore, North Korea slightly jams South Korean international shortwave broadcasts, called KBS World Radio on 5975 (discontinued as of early 2007) and 7275 kHz. The South Korean national radio channel, KBS Radio 1 on 711 kHz medium-wave, is also jammed by the North. If you go to coastal areas of the central part of the Yellow Sea and you tune in 711 kHz, you may hear unique, beeping sounds, which seem to be jamming signals from the North. Strangely, the North does not jam the medium-wave transmissions of a South Korea's broadcast towards-the-North, KBS Radio Social Education on 972 and 1134 kHz. On television broadcasting, jamming by the North is relatively unusual, although the North Korean regime once jammed a South Korean state-owned television broadcast (KBS TV1 on VHF ch. 9 in Seoul) in the 1970s and there might be some strange, minor signals on VHF ch. 9 in Seoul which seem to be North Korean's jamming. Because of electric lack in North Korea these days, the radio jamming activities are not always even; the jamming is sometimes interrupted by power failure.