ESAT RHM2 - PART3

198. Approximately how long is each leg of a symmetrical delta loop antenna driven element for 28.7 MHz?

199. An isotropic antenna is a:

200. The measurement of the amplitude of sound energy. Sometimes mistakenly called loudness.

201. Any disturbance that produces an undesirable response or degrades a wave.

202. Disturbances in the earth's magnetic field that make communications practical only at lower frequencies.

203. The radiation of energy equally in all directions.

204. Straight lines that represent light waves emitting from a source.

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

206. A single-mode fiber has a numerical aperture of 0.15. What is the maximum core diameter it could have for use with infrared light with a wavelength of 820 nm?

207. An optical fiber has a bandwidthdistance product of 500 MHz-km. If a bandwidth of 85 MHz is required for a particular mode of transmission, what is the maximum distance that can be used between repeaters?

208. Find the energy, in electron-volts, in one photon at a wavelength of 1 µm.

209. A fiber-optic link extends for 40 km. The laser-diode emitter has an output power of 1.5 mW, and the receiver requires a signal strength of –25 dBm for a satisfactory signal-to-noise ratio. The fiber is available in lengths of 2.5 km and can be spliced with a loss of 0.25 dB per spliced. The fiber has a loss of 0.3 dB/km. The total of all the connection losses at the two ends is 4 dB. Calculate the available system margin.

210. When reflection occurs, a wave strikes an object and bounces back ______.

211. It is the basic optical material property that measures the speed of light in an optical medium.

212. It occurs when light rays are totally reflected at the boundary between two different transparent materials.

213. It is the angle at which total internal reflection occurs.

214. Which is/are parts of an optical fiber?

215. What type of propagation usually occurs from one hand- held VHF transceiver to another nearby?

216. How does the range of sky-wave propagation compare to ground- wave propagation?

217. When a signal is returned to earth by the ionosphere, what is this called?

218. How are VHF signals propagated within the range of the visible horizon?

219. Skywave is another name for:

220. The part of a radiation pattern that is radiated in all directions along the horizontal plane.

221. The wave that strikes the surface of a medium or the wave that travels from the sending end to the receiving end of a transmission line.

222. The losses that occur when the electromagnetic field around a conductor cuts through a nearby metallic object and induces a current into that object.

223. The end of a two-wire transmission line that is connected to a source.

224. An antenna that is a wavelength or more long at its operating frequency.

225. A 45 km length of fiber must not lengthen pulses by more than 100 ns. Find the maximum permissible value for the pulse-spreading constant.

226. A fiber is rated as having a bandwidthdistance product of 500 MHz-km. Find its dispersion in ns/km, and find the rise time of a pulse in a 5 km length of this cable.

227. A fiber-optic system uses a detector with a rise time of 3 ns and a source with a rise time of 2 ns. If an RZ code is used with a data rate of 100 Mb/s over a distance of 25 km, calculate the maximum acceptable dispersion for the fiber and the equivalent bandwidthdistance product.

228. Calculate the energy of one photon for infrared light energy 1.55 µm. Calculate the power in a 1ms pulse of this energy.

229. Bound rays propagate through an optical fiber core by ______.

230. It is the maximum angle to the axis of the fiber that light entering the fiber is bound or propagated.

231. The wavelength of operation in fiber optics is between _____.

232. What causes the ionosphere to form?

233. What type of solar radiation is most responsible for ionization in the outer atmosphere?

234. Which ionospheric region is closest to the earth?

235. Which region of the ionosphere is the least useful for long distance radiowave propagation?

236. The curves of a standing wave or antenna that represent amplitude of current or voltage.

237. The properties of inductance, capacitance, and resistance in a transmission line.

238. The field produced when current flows through a conductor or antenna.

239. Interference that are ordinarily vertically polarized which are less likely to be picked up by horizontal antennas.

240. Maximum frequency that can be used for communications between two locations for a given time of day and a given angle of incidence.

241. Determine the cutoff wavelength for a fiber with a 3-µm-diameter core. The core and cladding indexes of refraction are 1.545 and 1.510, respectively.

242. Calculate the optical power 50km from a 0.1mW source on a single-mode fiber that has 0.25dB/km loss.

243. For a 300-meter optical fiber cable with a BLP of 600 MHz-km, determine the bandwidth.

244. For an optical fiber 10 km long with a pulse-spreading constant of 5 ns/km, determine the maximum digital transmission rates for RZ.

245. For an optical fiber 10 km long with a pulse-spreading constant of 5 ns/km, determine the maximum digital transmission rates for NRZ.

246. What two sub-regions of ionosphere exist only in the daytime?

247. What is a skip zone?

249. What is the maximum distance along the earth's surface that is normally covered in one hop using the E region?

250. Skip zone is:

251. The lobe in which the radiation intensity is less than a major lobe

252. An array that contains two or more parasitic elements and a driven element.

253. The line-of-sight horizon.

254. The fixed minimum points of voltage or current on a standing wave or antenna.

248. What is the maximum distance along the earth's surface that is normally covered in one hop using the F2 region?

255. A transmission line that has no standing waves of current or voltage.

256. The distance to Europe from your location is approximately 5000 km. What sort of propagation is the most likely to be involved?

257. What effect does the D region of the ionosphere have on lower frequency HF signals in the daytime?

258. What causes the ionosphere to absorb radio waves?

259. Two or more parts of the radio wave follow different paths during propagation and this may result in phase differences at the receiver. This "change" at the receiver is called:

260. A change or variation in signal strength at the antenna, caused by differences in path lengths, is called:

261. On a polar-coordinate graph, the area that represents minimum or 0 radiation.

262. A type of substance that does not transmit any light rays.

263. The most practical operating frequency that can be used with the least amount of problems.

264. The end of a transmission line that is opposite the source.

265. A circuit that acts as a high impedance at resonance.

266. When a transmitted radio signal reaches a station by a one-hop and two-hop skip path, small changes in the ionosphere can cause:

267. How do sunspots change the ionization of the atmosphere?

268. How long is an average sunspot cycle?

269. What is solar flux?

270. What is the solar-flux index?

271. An array that has one or more parasitic elements.

272. The amount of time required for completion of one full cycle.

273. The plane (vertical or horizontal) with respect to the earth in which the E field propagates.

274. A graph whose axes consist of a series of circles with a common center and a rotating radius extending from the center of the concentric circles.

275. The heat loss in a conductor as current flows through it.

276. What influences all radio communication beyond ground-wave or line-of-sight ranges?

277. What happens to signals higher in frequency than the critical frequency?

278. What causes the maximum usable frequency to vary?

279. What does maximum usable frequency mean?

280. What can be done at an amateur station to continue HF communications during a sudden ionospheric disturbance?

281. The colors of light (red, green, and blue), from which all other colors may be derived.

282. Waves traveling through a medium.

283. Same as the Marconi antenna.

284. The losses that occur when magnetic lines of force about a conductor are projected into space as radiation and are not returned to the conductor as the cycle alternates.

85. The resistance, which if inserted in place of an antenna, would consume the same amount of power as that radiated by the antenna.

286. What is one way to determine if the maximum usable frequency (MUF) is high enough to support 28 MHz propagation between your station and western Europe?

287. Which ionospheric region most affects sky-wave propagation on the 6 meter band?

288. What effect does tropospheric bending have on 2-meter radio waves?

289. What causes tropospheric ducting of radio waves?

290. That portion of the radiation kept close to the earth's surface due to bending in the atmosphere is called the:

291. The boundary beyond the natural horizon in which radio waves cannot be propagated over the earth's surface.

292. A longitudinal wave that has been expanded or made less dense as it moves away from the source.

293. The device used to pick up an rf signal from space.

294. The property of interchangeability of the same antenna for transmitting and receiving.

295. The position a particle of matter would occupy if it were not disturbed by wave motion.

295. The position a particle of matter would occupy if it were not disturbed by wave motion.

296. What is a sporadic-E condition?

297. What kind of propagation would best be used by two stations within each other's skip zone on a certain frequency?

298. If you receive a weak, distorted signal from a distance, and close to the maximum usable frequency, what type of propagation is probably occurring?

299. What is a characteristic of HF scatter signals?

300. What makes HF scatter signals often sound distorted?