Video Devices
Video senders typically operate using an FM carrier to carry a video signal from one room to another (for example, satellite TV or closed-circuit television). These devices typically operate continuously but have low (10 mW) transmit power. However, some devices, especially wireless cameras, operate with (often unauthorized) high power levels, and have high-gain antennas.
Amateur Radio operators can transmit two-way Amateur television (and voice) in the 2.4 GHz band - and all ISM frequencies above 902 MHz - with maximum power of 1500 watts.
Although the transmitter of some video cameras appears to be fixed on one frequency, it has been found in several models that the cameras are actually frequency agile, and can have their frequency changed by disassembling the product and moving solder links or dip switches inside the camera.
These devices are prone to interference from other 2.4 GHz devices, due to the nature of an analog video signal showing up interference very easily. A carrier to noise ratio of some 20 dB is required to give a "clean" picture.
Continuous transmissions interfere with these, causing "patterning" on the picture, sometimes a dark or light shift, or complete blocking of the signal.
Non-continuous transmissions, such as Wi-Fi, cause horizontal noise bars to appear on the screen, and can cause "popping" or "clicking" to be heard on the sound.
Read more about this topic: Electromagnetic Interference At 2.4 GHz
Famous quotes containing the words video and/or devices:
“We attempt to remember our collective American childhood, the way it was, but what we often remember is a combination of real past, pieces reshaped by bitterness and love, and, of course, the video past—the portrayals of family life on such television programs as “Leave it to Beaver” and “Father Knows Best” and all the rest.”
—Richard Louv (20th century)
“The relationship between mother and professional has not been a partnership in which both work together on behalf of the child, in which the expert helps the mother achieve her own goals for her child. Instead, professionals often behave as if they alone are advocates for the child; as if they are the guardians of the child’s needs; as if the mother left to her own devices will surely damage the child and only the professional can rescue him.”
—Elaine Heffner (20th century)