Train free essay sample

In analog technology, compare and contrast the advantages and disadvantages of amplitude modulation, frequency modulation, phase modulation, and Quadrature Amplitude Modulation There are several advantages of amplitude modulation, and some of these reasons have meant that it is still in widespread use today. It is simple to implement, it can be demodulated using a circuit consisting of very few components, and AM receivers are very cheap as no specialized components are needed (Electronics and Radio Today,  n. We will write a custom essay sample on Train or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page d. ). Disadvantages: Amplitude modulation is a very basic form of modulation, and although its simplicity is one of its major advantages, other more sophisticated systems provide a number of advantages. Accordingly it is worth looking at some of the disadvantages of amplitude modulation. It is not efficient in terms of its power usage, it is not efficient in terms of its use of bandwidth, requiring a bandwidth equal to twice that of the highest audio frequency, and it is prone to high levels of noise because most noise is amplitude based and obviously AM detectors are sensitive to it (Electronics and Radio Today,  n. d. ). Frequency Modulation Frequency nodulation (FM) sends information over a carrier wave by varying its instantaneous frequency. In analog applications, the difference between the instantaneous and the base frequency of the carrier is directly proportional to the instantaneous value of the input-signal amplitude. FM is commonly used for broadcasting music and speech, two way radio systems, magnetic tape recording systems, and some video transmission systems. FM signals can be generated using either direct or indirect frequency modulation. Direct FM modulation can be achieved by directly feeding the message into the input of a voltage controlled oscillator (VCO). For indirect FM modulation, the message signal is integrated to generate a phase-modulated signal. This is used to modulate a crystal-controlled oscillator, and the result is passed through a frequency multiplier to give an FM signal (Electronics and Radio Today,  n. d. 1). FM is used for a number of reasons and there are several advantages of frequency modulation. In view of this it is widely used in a number of areas to which it is ideally suited. Some of the advantages of frequency modulation are noted below: Resilience to noise: One particular advantage of frequency modulation is its resilience to signal level variations. The modulation is carried only as variations in frequency. This means that any signal level variations will not affect the audio output, provided that the signal does not fall to a level where the receiver cannot cope. As a result this makes FM ideal for mobile radio communication applications including more general two-way radio communication or portable applications where signal levels are likely to vary considerably. The other advantage of FM is its resilience to noise and interference. It is for this reason that FM is used for high quality broadcast transmissions. Easy to apply modulation at a low power stage of the transmitter: Another advantage of frequency modulation is associated with the transmitters. It is possible to apply the modulation to a low power stage of the transmitter, and it is not necessary to use a linear form of amplification to increase the power level of the signal to its final value. It is possible to use efficient RF amplifiers with frequency modulated signals: It is possible to use non-linear RF amplifiers to amplify FM signals in a transmitter and these are more efficient than the linear ones required for signals with any amplitude variations (e. . AM). This means that for a given power output, less battery power is required and this makes the use of FM more viable for portable two-way radio applications (Electronics and Radio Today,  n. d. 1). Phase Modulation Phase modulation (PM) is a form of modulation that represents information as variations in the instantaneous phase of a carrier wave. Unlike its more popular counterpart, frequency modulation (FM), PM is not very widely used for radio transmissions. This is because it tends to require more complex receiving hardware (Radio-Electronics. com,  n. d. ). Advantage: The main advantage of PM like FM is increased immunity to noise. Disadvantage: The main disadvantage to PM is that it requires more complex receiving hardware (M. S. Richer,  2006). Quadrature Amplitude Modulation Quadrature amplitude modulation (QAM) is both an analog and a digital modulation scheme. It conveys two analog message signals, or two digital bit streams, by changing (modulating) the amplitudes of two carrier waves. The two carrier waves, usually sinusoids, are out of phase with each other by 90 ° and are thus called quadrature carriers or quadrature components. Analog QAM is used in National Television System Committee (NTSC) and Phase Alternating Line (PAL) television systems (Radio-Electronics. com,  n. d. ). Advantages: With QAM sharp cutoff band pass filters are not required. This makes it an attractive alternative to single sideband-suppressed carrier (SSB-SC). Disadvantages: Compared to SSB, QAM is more exacting in terms of the carrier

The Weather - English Vocabulary in Examples

The Weather s Here are words used to describe the weather from stormy days to beautiful sunny days on the beach. Words are categorized into different sections. Youll find example sentences for each word to help provide context for learning. Speaking about the weather is often considered important for small talk, and used to make predictions about the weather.   The Weather - Describing the Weather (Adjectives) The following are all words that are often used to describe the weather: breezy - Its very breezy today. I think its a northern wind.bright - They got married on a bright, sunny day in June.clear - Wait till the weather is clear to take a bike ride.cloudy - Some people prefer to hike when its cloudy rather than when its sunny.damp - I hate damp, cold days when I cant warm up.drizzly - The weather is rather drizzly today. You should take a rain jacket.dry - Next week will be hot and dry.dull - The weather is dull this week. I wish it would rain.foggy - The foggy bay can be dangerous if you arent careful.hazy - Its so hazy today that I cant see any of the mountains.rainy - The weather in Portland is often rainy.showery - Spring weather often features showery days followed by a few days of sunshine.snowy - If you are a skier, youll be happy to know that it will be snowy next week.stormy - The stormy weather put him into a foul mood.sunny - I want to go anywhere thats sunny and mild.wet - Winter is usually very wet in the Northwest.   The Weather - Nouns breeze - Theres a gentle breeze blowing today.cloud - Do you see that cloud that looks like a cow?drizzle - When will this steady drizzle stop?!fog - Theres a thick fog on the bay this morning.hailstone - The hailstone broke the window.haze - The haze is very thick in the air today. Maybe theres a fire in the hills.lightning - The lightning frighted the children as it flashed.rain - We expect more than four inches of rain on Saturday.raindrop - The raindrop ran down her cheek.rainfall - The rainfall thundered on the roof.shower - We had quite a shower this morning. Im still wet!snow - Taking a walk in the snow is very peaceful.snowfall - The snowfall continued through the night.snowflake - Did you know that every snowflake is unique?storm - The storm raged for three days and left ten dead,sun - Without the sun, we have no life.sunshine - The sunshine shone through the window.thunder - The loud thunder could be heard for miles.wind - The wind blew 40 miles per hour. The Weather - The Temperature (Adjectives) chilly - Its very chilly this morning.cold - Take your jacket. Its cold out!freezing  - Im going to wear gloves as its freezing.hot - I like hot, lazy days on the beach.mild - Its best to go hiking in mild weather thats not too hot.scorching - Its scorching in the dessert. Be careful.warm - Its a beautiful, warm afternoon.   The Weather - Verbs glow - The sun glowed as it set in the west.freeze - The rain might freeze on the trees tonight.hail - It hailed so hard it looked like snow.pour - The rain poured for three days.rain - Its raining outside.shine - The sun shone through the trees.snow - It snowed three inches last night.   The Weather - Idioms As right as rain Everything is OK, or good in a situation / I feel as right as rain today. Itll be a good day.Be a breeze Be easy, no problems / Dont worry about the test. Itll be a breeze.  Be on cloud nine be extremely happy or even ecstatic /  He was on cloud nine after he met her.  Break the ice begin a conversation / Ill break the ice by introducing myself.The calm before the storm A period of uneasy stillness before something bad happens / It feels like the calm before the storm. I hope hes not too angry.Come rain or shine Something will happen despite any problems /  Were going to play baseball come rain or shine.  It never rains, but it pours Bad news or problems tend to come together in large groups / When you have problems it feels like it never rains, but it pours.

Mbuti Culture Research Paper Example | Topics and Well Written Essays - 2000 words

Mbuti Culture - Research Paper Example The Mbuti tribe is dependent on the forest for all the aspects of their life including getting their food, clothes, materials for hunting, item of play, musical instrument etc. In the recent times the tribesmen have come in contact with the agricultural people living the peripheries of the forest. However hunting remains their primary source of subsistence. Even in their trade with the agricultural people they exchange the meat they get from the forest in exchange for farm products (Tanno, n.d. pp. 1-51). The forest and hunting activities influenced the culture, social structures, gender relations and the beliefs and values of the Mbuti tribe associated with the Molimo ritual of the tribe. Social Organization The difference in the strategy for procuring the subsistence has attracted the interest of the anthropologist and ethnographers. Along with the difference in the hunting technique some difference in the social structure has also been observed with reference to the number of memb ers in the community. The inhabitants of the southwestern region, the net hunters live in a comparatively large camp consisting to seven to thirty families together. There method of hunting and distribution of the hunt are also of communal type. The women beat the under bush to drive the animals to the net which are looked after by the men. According to famous pygmy researcher Turnbull, this method of hunting requires a number of families to cooperate with each other in order to procure their subsistence. On the contrast the archers live in small groups of three to five. Individual members hunt with the help of arches and bows. The different operations of arching are tracking and ambushing which requires less number of men than net hunting. Several reasons have been cited for this difference in hunting pattern and consequent social structure based on region. According to Turnbull, this has occurred due to the historical distribution of the forest. The southwestern parts of the count ries have been subjected to encroachment for agriculture, mining, plantations, tourist centers etc. As a result the inhabitable land and the land for hunting and gathering have been reduced. On the other hand the population of the tribe has increased over the years. As a result the tribe was forced to increase their utilization of the reduced amount of available land. Moreover due to the Law of Diminishing Return the tribesmen had to undertake more work individually in order to maintain similar level of consumption. Another interesting feature that has been pointed out by the scholars is that the pygmy tribe has a low exposure to the technological advancement. Therefore they are unable to increase the utilization of the plot of land with the help of technology. To compensate for that, the tribesmen are required to increase the coordination and cooperation among themselves to maintain similar level of consumption. (Abruzzi, 1979) Renowned anthropologist, Harako suggests another alter native theory. According to him the original mode of hunting of the Mbuti tribe was archery. But some time in history a part of the tribe came in touch with the Bantu speaking tribes. In course of their interaction and exchange the Mbuti tribe learnt to use the net as a tool for hunting. This theory gives an explanation for the division of hunting methods