With the installation of more and more satellites to receive cable TV, the radio and television network department has adopted terrestrial satellite signal jammers to carry out local microwave interference to the places where there are many users of satellite antennas, so that the picture of satellite TV reception appears static, Phenomena such as black screen and mosaic.
So let's take a look at the structure and working principle of the jammer.
The composition of the jammer
The ground satellite signal jammer consists of a transmitter and a horn antenna. The housing of the transmitter is similar to the antenna on a cable TV. Satellite communication is a universal signal resource stipulated internationally and is protected, and no human interference is allowed for any reason. Relevant national units expressly prohibit the installation of domestic jammers, because after the jammer's power reaches a certain level, it will seriously affect the work of national defense and news organizations.
Type of interference
The ground satellite signal jammer can be divided into digital TV image signal interference and carrier (or narrowband) signal interference from the interference means. The former uses illegal image interference, that is, uses the same digital form as the normal broadcast signal to make the normal image appear mosaic or black. Interference is dominated by power occupation, that is, high-power co-frequency signals are transmitted in the same direction, and the satellite receiving channel is occupied in a certain frequency range, so that the field strength of the interference signal is far greater than the signal field strength of the normal satellite reaching the ground. The purpose of suppressing satellite signal reception; the latter is divided into co-channel interference and non-co-channel interference. For co-channel interference, the interference signal can cause serious mosaic or pauses in the image, and black screens will appear when the interference is serious. For non-co-channel interference, due to the frequency selection effect of the satellite receiver, the interference level is allowed to be greater than the signal level, but if the interference level is so large that the tuner enters a saturated state, the TV screen will appear black at this time. However, satellite signal jammers are limited by distance and azimuth. Because the propagation loss of the transmitted interference microwave is related to the working frequency and propagation distance, under the conditions of free space propagation, the longer the distance, the worse the interference ability. For the 3.7GHz～4.2GHz satellite signal interference system, the transmission distance generally does not exceed 3km.
It is worth mentioning that the current terrestrial satellite signal jammers generally interfere with C-band signals and have little effect on Ku-band signals. Because the Ku-band operating frequency is too high, the required components are expensive, and the production and debugging are difficult, so it is very rare.
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