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For very low-power systems, such as mobile phones, signal strength is usually expressed in dB-microvolts per metre (dBμV/m) or in decibels above a reference level of one milliwatt . In broadcasting terminology, 1 mV/m is 1000 μV/m or 60 dBμ (often written dBu). Examples. 100 dBμ or 100 mV/m: blanketing interference may occur on some receivers
Outdoor antennas provide up to a 15 dB gain in signal strength and 15-20 dB greater rejection of ghost signals in analog TV. [6] Combined with a signal increase of 14 dB due to height and 11 dB due to lack of attenuating building walls, an outdoor antenna can result in a signal strength increase of up to 40 dB at the TV receiver. [6]
The first technique developed was the far-field range, where the antenna under test (AUT) is placed in the far-field of a range antenna. Due to the size required to create a far-field range for large antennas, near-field techniques were developed, which allow the measurement of the field on a distance close to the antenna (typically 3 to 10 ...
A coverage map may be produced to indicate the area in which a certain signal strength is delivered. [1] Even if it is 100% accurate (which it never is), a major factor on whether a signal is receivable depends very much on whether the receiving apparatus is sensitive enough to use a signal of that level.
It is possible to also get a bad picture if the signal strength of the TV transmitter is too high. An attenuator inserted in the antenna lead-in wire may be used if the television receiver displays signs of overload in the RF front end. Strong out-of-band signals may also affect television reception and may require band-pass filters to reduce ...
Satellite radio also is designed to switch seamlessly between repeaters and/or satellite when moving outside the range of one or the other. HD Radio switches back to the analog signal as a fallback when the edge of the digital range is encountered, but the success of this from the listener's perspective depends on how well the station's ...
Now consider the case when the antenna is fed a signal with a wavelength of 1.25 m; in this case the current induced by the signal would arrive at the antenna's feedpoint out-of-phase with the signal, causing the net current to drop while the voltage remains the same. Electrically this appears to be a very high impedance.
The ATSC signal is more susceptible to changes in radio propagation conditions than DVB-T and ISDB-T. It also lacks true hierarchical modulation, which would allow the SDTV part of an HDTV signal (or the audio portion of a television program) to be received uninterrupted even in fringe areas where signal strength is low.