ESAT RHM 2 - PART 2

99. If an antenna is made shorter, what happens to its resonant frequency?

100. The wavelength for a frequency of 25 MHz

101. The velocity of propagation of radio frequency energy in free space is:

102. How do you calculate the length in meters (feet) of a quarter-wavelength vertical antenna?

103. The scattering of reflected light waves (beams) from an object, such as white paper.

104. Radiation that varies with direction.

105. The property of an array that causes more radiation to take place in certain directions than in others.

106. The constants of inductance, capacitance, and resistance in a transmission line. The constants are spread along the entire length of the line and cannot be distinguished separately.

107. Another name for the dipole antenna.

108. A pulse sent to a target returns after 15µs. How far away is the target?

109. A pulse radar emits pulses with a duration of 1 µs and a repetition rate of 1 KHz. Find the maximum range for this radar.

110. Find the Dopper shift caused by a vehicle moving towards a radar at 60 mph, if the radar operates at 10 GHz.

The system operates at a bit rate of 40 Mb/s. Calculate the energy per bit to noise density ratio, in decibels if the power received is 631 pW.

112. Consider a space-diversity microwave radio system operating at an RF carrier frequency of 1.8 GHz. Each station has a 2.4-m-diameter parabolic antenna that is fed by 100 m of air-filled coaxial cable. The terrain is smooth, and the area has a humid climate. The distance between stations is 40 km. A reliability objective of 99.99% is desired. Determine the system gain.

113. Intrinsic absorption in the ultraviolet region is caused by _______.

114. What is the main cause of intrinsic absorption in the infrared region?

115. Caused by impurities introduced into the fiber material.

116. Caused by the electronic transition of these metal ions from one energy level to another.

117. Caused by the interaction of light with density fluctuations within a fiber.

118. Most new communication satellites will operate in which band?

119. One system for effectively doubling the bandwidth and information-carrying capacity of a satellite is known as

120. Uplink signals are amplified, translated in frequency, and retransmitted on the downlink to one or more earth stations by a(n)

121. A typical commercial communication satellite contains

122. Large arrays of photocells connected in various series and parallel circuits to create a power source of direct current are

123. If you made a quarter-wavelength vertical antenna for 21.125 MHz, how long would it be?

124. If you made a half-wavelength vertical antenna for 223 MHz, how long would it be?

125. Why is a 5/8-wavelength vertical antenna better than a 1/4-wavelength vertical antenna for VHF or UHF mobile operations?

126. If a magnetic-base whip antenna is placed on the roof of a car, in what direction does it send out radio energy?

127. How many directly driven elements do most Yagi antennas have?

128. An element of an antenna (transmitting or receiving) that is connected directly to the transmission line.

129. The ability of a substance to return to its original state.

130. Man-made or natural interference that degrades the quality of reception of radio waves.

131. The field produced as a result of a voltage charge on a conductor or antenna.

132. Connecting one end of an antenna through a capacitor to the final output stage of a transmitter.

133. For an equivalent noise bandwidth of 10 MHz, determine the minimum receive carrier power if the C/N is 24dB.

134. For an equivalent noise bandwidth of 10 MHz, determine a minimum transmit carrier power if the system gain is 113.35dB.

135. For a total transmit power of 1000 W, determine the energy per bit (Eb) for a transmission rate of 50 Mbps.

136. For an earth station transmitter with an antenna output power of 40dBW (10,000 W), a back-off loss of 3dB, a total branching and feeder loss of 3dB, and a transmit antenna gain of 40dB, determine the EIRP.

137. Find the velocity and the orbital period of a satellite in a circular orbit 36,000 km above the earth’s surface (approximately the height of a geosynchronous satellite).

138. Occurs when the size of the density fluctuation is less than one-tenth of the operating wavelength of light.

139. Loss caused by Rayleigh scattering is proportional to the _______ of the wavelength.

140. It is classified according to the bend radius of curvature.

141. Small microscopic bends of the fiber axis that occur mainly when a fiber is cabled.

142. Bends having a large radius of curvature relative to the fiber diameter.

143. A waveguide assembly that permits both the transmitter and the receiver to use the same antenna is a

144. What consists of all the electronic equipment that takes the signal to be transmitted, amplifies it, and sends it to the antenna?

145. Which of the following is not a benefit of using plastic fiber-optic cables rather than glass fiber-optic cables?

146. Which fiber-optic cable is widely used at short to medium distances, is easiest to make, and is the least expensive?

147. A newer and better way to deal with dispersion that uses equalization techniques to adjust the received waveform to compensate for dispersion is

148. Approximately how long is the driven element of a Yagi antenna for 14.0 MHz?

149. Approximately how long is the director element of a Yagi antenna for 21.1 MHz?

150. Approximately how long is the reflector element of a Yagi antenna for 28.1 MHz?

151. What is one effect of increasing the boom length and adding directors to a Yagi antenna?

152. If you made a half-wavelength dipole antenna for 28.550 MHz, how long would it be?

147. A newer and better way to deal with dispersion that uses equalization techniques to adjust the received waveform to compensate for dispersion is

153. Variations in signal strength by atmospheric conditions.

154. A transmission line that has no standing waves. This line requires no special tuning device to transfer maximum power.

155. An ordinary half-wave antenna (dipole) that has one or more additional conductors connected across the ends parallel to each other.

156. The loss of energy of a radio wave because of the spreading of the wavefront as it travels from the transmitter.

157. Transmitting (and receiving) of radio waves on two different frequencies simultaneously.

158. Calculate the angle of declination for an antenna using a polar mount at a latitude of 45°.

159. Calculate the length of the path to a geostationary satellite from an earth station where the angle of elevation is 30°.

160. A satellite transmitter operates at 4 GHz with a transmitter power of 7W and an antenna gain of 40 dBi,. The receiver has an antenna gain of 30 dBi, and the path length is 40,000 km. Calculate the signal strength at the receiver.

161. A receiving antenna with a gain of 40 dBi looks at a sky with a noise temperature of 15 K. The loss between the antenna and the LNA input, due to the feedhorn, is 0.4 dB, and the LNA has a noise temperature of 40 K. Calculate G/T.

162. The receiving installation whose G/T was used as a ground terminal to receive a signal from a satellite at a distance of 38,000 km. The satellite has a transmitter power of 50 watts and an antenna gain of 30 dBi. Assume losses between the satellite transmitter and its antenna are negligible. The frequency is 12 GHz. Calculate the carrier-to-noise ratio at the receiver, for a bandwidth of 1 MHz. G/T=20.6.

163. How can fiber sensitivity to bending losses can be reduced?

164. The following can cause microbending loss:

165. Same as intramodal dispersion:

166. Same as intermodal dispersion:

167. What happens as pulse spreads?

168. Which of the following is not one of the most important specifications of a fiber-optic cable?

169. Which of the following terms refers to how light energy is converted to heat in the fiber-optic core material because of the impurity of glass or plastic?

170. In a fiber-optic cable, what determines the maximum speed of the data pulses the cable can handle?

171. Which of the following light sources cannot be used in fiber-optic systems?

172. The most widely used light source in fiber-optic systems is the

174. The fastest and most sensitive photodiode available is the

175. What is one disadvantage of a random wire antenna?

176. What is the low angle radiation pattern of an ideal half-wavelength dipole HF antenna installed parallel to the earth?

177. The impedances in ohms at the feed point of the dipole and folded dipole are, respectively:

178. A dipole transmitting antenna, placed so that the ends are pointing North/South, radiates:

179. What is a cubical quad antenna?

180. The basic frequency or first harmonic freq.

181. A type of antenna that uses a ground plane as a simulated ground to produce low-angle radiation.

182. A series of conductors buried below the surface of the earth and arranged in a radial pattern. Used to reduce losses in the ground.

183. An antenna consisting of two rods (1/4 wavelength each) in a straight line, that radiates electromagnetic energy.

184. A half-wave antenna installed some distance above ground and positioned either vertically or horizontally.

185. Telephone communication takes place between two earth stations via a satellite that is 40,000 km each station. Suppose Bill, at station 1, asks a question and Sharon at station 2, and answers immediately, as soon as she hears the question. How much time elapses between the end of Bill’s question and the beginning of Sharon’s reply, as heard by Bill?

186. A typical TVRO installation for use with C-band satellites (downlink at approximately 4 GHz) has a diameter of about 3m and an efficiency of about 55%. Calculate its gain and beamwidth.

187. A fiber has an index of refraction of 1.6 for the core and 1.4 for the cladding. Calculate the critical angle.

188. A fiber has an index of refraction of 1.6 for the core and 1.4 for the cladding. Calculate the θ2 for θ1=30°.

189. A fiber has an index of refraction of 1.6 for the core and 1.4 for the cladding. Calculate the numerical aperture.

190. When different colors of light travel through different materials and different waveguide structures at different speeds,______ will happen.

191. _________ occurs because the spreading of a light pulse is dependent on the wavelengths' interaction with the refractive index of the fiber core.

192. __________occurs because the mode propagation constant (β) is a function of the size of the fiber's core relative to the wavelength of operation.

193. It causes the input light pulse to spread.

194. When they encounter any substance, they are either transmitted, refracted, reflected, or absorbed.

195. What is a delta loop antenna?

196. Approximately how long is each side of a cubical quad antenna driven element for 21.4 MHz?

197. Approximately how long is each side of a cubical quad antenna driven element for 14.3 MHz?