ESAT RHM 1 PART 2

101. What happens to the feed point impedance of a ground-plane antenna when its radials are changed from horizontal to downward-sloping?

102. The portion of a groundplane antenna that acts as ground.

103. The impedance presented to the transmitter by the transmission line and its load.

104. In a Morse code transmission, local RF interference (key-clicks) is produced by:

105. A parasitic oscillation:

106. Transmitter RF amplifiers can generate parasitic oscillations:

107. A receiver has an equivalent noise figure of 3 dB. Calculate its equivalent noise temperature.

108. A flexible coaxial line contains:

109. A 75 ohm transmission line could be matched to the 300 ohm feedpoint of an antenna:

110. They used specially-cut crystals to control the frequency.

111. Have extremely good selectivity

112. Provide the desired frequency response but have a constant time delay in the passband.

113. It is the frequency to which a radio signal is converted during heterodyne reception.

114. It is the minimum RF signal level that can be detected at the input to the receiver and still produce a usable demodulated information signal.

115. Find the output power 20km away from a source if the line is rated with an attenuation of 0.2dB/km. The source power is 4.4mW.

116. It is the ratio of the bandwidth 60 dB below maximum signal level and bandwidth 3 dB below maximum signal level.

117. Consists of a center conductor surrounded by a dielectric material, then concentric shielding, and finally a rubber environmental protection outer jacket.

118. It consists of a flexible inner conductor and a concentric outer conductor of metal braid, the two are separated by a continuous insulating material.

119. Also known as bayonet mount as they can easily twisted on or off.

120. It is the difference between the power delivered to the antenna to the actual power it radiates.

121. Defined as the ratio of the radiation resistance to the total antenna resistance.

122. It is defined as the maximum directive gain, and it is defined as the ability of an antenna to focus energy in a particular direction.

123. An audio signal of amplitude one half the carrier amplitude is used in amplitude modulation. Calculate the modulation index?

124. An area of a radiation pattern plotted on a polar-coordinate graph that represents maximum radiation.

125. The speed of a radio wave:

126. To lower the resonant frequency of an antenna, the operator should:

127. The wavelength corresponding to a frequency of 2 MHz is:

128. It is the noise-reduction effect that occurs with strong FM signals.

129. The antenna current of an AM transmitter is 15 amperes when only the carrier is sent but it increases to 17.10 amperes when the carrier is sinusoidally modulated. How many percent the carrier is modulated?

130. It is a modulation technique where the information signal is analog and the phase of the carrier is varied proportional to the information signal.

131. It flares out in one direction only and is equivalent of a pillbox parabolic reflector.

132. It is a logical termination for a circular waveguide.

133. The primary antenna is placed at the focus.

134. The insertion of an inductor or capacitor in series with an antenna to lengthen or shorten the antenna electrically.

135. A quarter-wave antenna oriented perpendicular to the earth and operated with one end grounded.

136. What is meant by harmonic radiation?

137. What type of interference may come from a multi- band antenna connected to a poorly tuned transmitter?

138. What causes splatter interference?

139. Why does coaxial cable make a good antenna feed line?

140. What are some reasons not to use parallel- conductor feed line?

141. What common connector usually joins a hand-held transceiver to its antenna?

142. It is more than half duplex but less than full duplex, and it is more of an error detection scheme rather than a transmission mode.

143. A unit on a natural logarithmic scale for expressing the relationship between two amounts of power (as electric power or acoustic power) equal to one half the natural logarithm of the ratio of the two powers compared : 8.686 decibels

144. A (75 - j40) ฮฉ load is connected to a co-axial line of Z0 = 75 ฮฉ at 6 MHz. The load matching on the line can be accomplished by connecting:

145. Occurs only in devices where single current separates into two or more paths.

146. It is the corresponding reduction in the noise figure due to the reduction in bandwidth expressed mathematically in decibels.

147. The local oscillator frequency is tuned to a frequency lower than the input RF frequency

148. It is the numerical measure of the ability of a pre-selector to reject the image frequency.

149. Refers to the woven stranded mesh that surrounds some types of coaxial cables.

150. Consists of two layers of foil insulation and two layers of braided metal shielding

151. It is the measure of the resistance of a material against the formation of a magnetic field, otherwise known as distributed inductance in transmission line theory.

152. What is the propagation time if the distance between the two points is 12,000 km? Assume the propagation speed to be 2.4 x 108 m/s in cable.

153. It is a directivity pattern wherein energy is radiated equally in all directions.

154. It is a directivity pattern wherein energy is focused in only one direction.

155. It is the range of frequencies over which an antenna will radiate effectively or satisfactorily.

156. Transmitting in all directions.

157. The gain of an antenna, especially on VHF and above, is quoted in dBi. The "i" in this expression stands for:

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

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

160. The impedance presented to the load by the transmission line and its source.

161. The passive element of an antenna array that is connected to neither the transmission line nor the driven element.

162. One possible cause of TV interference by harmonics from an SSB transmitter is from "flat topping" โ€” driving the final amplifier into non- linear operation. The most appropriate remedy for this is:

163. An interfering signal from a transmitter is found to have a frequency of 57 MHz (TV Channel 2 is 54 - 60 MHz). This signal could be the:

164. What type of filter might be connected to an amateur HF transmitter to cut down on harmonic radiation?

165. If you install a 6 metre Yagi antenna on a tower 50 metres from your transmitter, which of the following feed lines is best?

166. What commonly available antenna feed line can be buried directly in the ground for some distance without adverse effects?

167. TV twin-lead feed line can be used for a feed line in an amateur station. The impedance of this line is approximately:

168. It is an irregular, random variation produced by any modification to a stream of carriers as they pass from input to output of a device.

169. These are large noise spiked present in the avalanche current due to oscillation that result in the avalanching region.

170. It is a noise having a power density that decreases by 3dB per octave.

171. This is used to keep the receiver audio turned off until an RF signal appears at the receiver input.

172. It is the RMS power developed at the crest of the modulation envelop.

173. An antenna has an impedance of 40 ฮฉ. An unmodulated AM signal produces a current of 4.8 A. The modulation is 90 percent. Calculate the carrier power.

174. A method in generating SSB that make us of two balanced modulators and two phase shifters.

175. These are the transmission characteristics of a transmission line.

176. What is a delta loop antenna?

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

178. Which statement about two- element delta loops and quad antennas is true?

179. Is used to express the attenuation and the phase shift per unit length of the transmission lines.

180. It is simply the relative permittivity of a material, and it depends on the type of insulating material used.

181. It is defined as the product of the power fed to an antenna and its power gain.

182. It is the rate at which energy flows through a unit area of surface in space.

183. It is the power density in space and the actual power that a receive antenna produces at its output terminals.

184. The electromagnetic field that detaches itself from an antenna and travels through space.

185. If an antenna is made longer, what happens to its resonant frequency?

186. The wavelength for a frequency of 25 MHz is:

187. Adding a series inductance to an antenna would:

188. It is also known as acquisition range where the PLL can establish or acquire lock with an input signal.

189. It uses a high pass filter, wherein the high- frequency modulating signals are emphasized or boosted in amplitude in the transmitter prior to performing modulation.

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

191. What is a disadvantage of using an antenna equipped with traps?

192. The "doublet antenna" is the most common in the amateur service. If you were to cut this antenna for 3.75 MHz, what would be its approximate length?

193. The standard cut-off frequency used for the filters in the emphasis networks.

194. It is a popular type of parasitic array using rectangular or diamond-shaped full-wave wire loop elements.

195. It consists of a loosely wound helix that is usually made up of six to eight turns of heavy wire or tubing and it is fed with coax and is backed up with a reflector.

196. The radiation is in the axial direction and produces a broadband and directional pattern

197. A crystal oscillator is accurate within ยฑ0.005%. How far off frequency could its output be at 270 MHz?

198. The parasitic element of an array that causes maximum energy radiation in a direction toward the driven element.

199. A coxial line consisting of a central, insulated wire (inner conductor) mounted inside a tubular outer conductor.

200. What circuit blocks RF energy above and below a certain limit?