![]() ![]() Thus, the pager must be isolated from extraneous signals. Even if an RF input jack was provided, paging signals in the area might be strong enough to invalidate test results. In addition, many pagers don’t provide a direct input to the receiver for connection to a signal generator. Testing pager sensitivity presents some difficulty because pager transmitters are very busy and produce very strong signals that can interfere with test results. However, a negative gain is actually a loss, so the pager’s internal antenna has a handicap of 22 dB compared with a half-wave dipole. Thus, the pager’s internal antenna has a gain of -22 dBd. Since a half-wave dipole would produce a level of 6.28 µV, the gain of the pager’s internal antenna can be determined as shown in Equation 2. Thus, we can assume that a field strength of 25 µV/m would produce an input level of 0.5 µV at the pager input. According to the specifications, the chassis sensitivity of the pager is 0.5 µV. Thus, a half-wave dipole in a field strength of 25 µV/m would produce 6.28 µV at the receiver input. ![]() Plugging the given figures into Equation 1 would yield 6.28 µV. Equation 1 provides the formula for calculating microvolts (µV) from microvolts-per-meter (µV/m). Since we are using a half-wave dipole, G R is equal to 0. First, we must know how many microvolts would appear across the terminals of a half-wave dipole when placed in a field strength of 25 µV/m. From this information, we can determine the amount of gain of the internal antenna in dBd. Suppose the sensitivity of a voice pager is given as 25 µV/m (microvolts per meter) in terms of field strength, or 0.5 µV chassis sensitivity, at a frequency of 160 MHz. This article will describe the relationship between several of the more frequently used units of measure and how they are applied in practice. It is imperative that wireless communication technicians understand the various units of measurement used to quantify the level or amplitude of a radio frequency, or RF, signal. ![]()
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