Short wave transmitter Tesla KRV 1/B

These short-wave transmitters could be tuned from 3 to 20 MHz and weighted approx. 600 kg. They were designed for AM radio broadcast, but were mainly used for jamming of foreign short-wave broadcasts such as the Voice of America or the Radio Free Europe. A jamming facility was placed near every big city and sent humming or noise on the same frequency as the foreign station. The foreign transmitters constantly changed frequency. The listeners could easily tune their receivers to the new frequency, but tuning the jammers took some time, during which the reception was clear. Today, the Chinese government continues to jam unwanted stations, but uses traditional Chinese music instead of noise.