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1、1 无线电广播和收音机基本原理（1 basic principles of radio and radio）Numerous households very bright day, the new peach old fu. Do unto you. Misfortune is the foundation of fortune, fortune is the root of misfortune. Once Lianjiu bird, fish think therefore abyss. This article is made up of silkworm baby boyPpt doc
2、uments may experience poor browsing on the WAP side. It is recommended that you select TXT first or download the source file to the local machine.Radio and radio brief history, who invented the radio? Western recognized Marconi, Russia only recognized Popov. This issue has been debated for more than
3、 a century and has not yet been completely united. Western countries believe that the invention of the signal carried on the airwaves for telecommunications transmission is the Italy electrical technician Marconi. The first test was in 1894, which became the beginning of radio technology. The Russia
4、ns believe that in 1894, Popov made a radio receiver, the first time he used the antenna in the receiver. Its also the first antenna in the world.In 1902, American history top use of homemade Feide ore radio complete radio experiment; the 1904 British physicist who invented the worlds first electric
5、 dipole; in 1906, American inventor de Foster assembled the first vacuum tube amplifier, the amplifier was immediately used to combine with the invention of radio Marconi, radio transmission using a human voice, so the radio. Canadian Reginald Aubrey Fessenden set up a pilot radio station in Brant R
6、oque, Massachusetts, on the eve of Christmas on 1906, the first broadcast program.In 1910, the first radio station was founded in Sanjose Charles Herold Radio School in California. Its the longest radio station in the world that hasnt stopped. In 1920, the first modern commercial radio station was f
7、ounded in Pittsburgh in November 2, 1920, it formally launched. More than 20 years later, FM radio was born, and FM stereo broadcasting didnt appear until 1962.What is wave?Velocity = wavelengthelectromagnetic waveMW: 10 kHz in China9 kHz in the United StatesShort wave: 10 kHz (digital radio tuned b
8、y 5 kHz) FM: 200 kHz (digital radio tuned at 100 kHz)Division and application of radio wave (frequency division and radio frequency band)The name of long wavelength band of MW and SW VHF (ultrashort wave) decimeter centimeter wave millimeter wavelength range of 108104 m 104103 m 103102m 10210 m 101m
9、 10010cm 101cm 101mm 3Hz30kHz 30300kHz 300kHz3MHz 330MHz 30300MHz frequency range 300M3GHz 330GHz 30300GHz band name VLF (VLF) LF (low frequency) MF (MF) HF (high frequency) VHF (VHF) main use audio, telephone, data terminal, navigation beacon, power line communication AM radio, amateur radioMobile
10、phones, shortwave radio, amateur radioFM broadcasting, TV, navigation mobile communicationUHF (ultra high frequency) TV, remote control, telemetry, radar, mobile communications SHF (UHF) EHF (extremely high frequency) microwave communications, satellite communications, radar, microwave communication
11、s, radar, radio astronomyName long waveReferred to as SW MW SW 120 m SW 90 m SW 75 m SW 60 m SW 49 m SW 41 m SW 31 m SW 25 m SW 19 m SW 16 m SW 13 m SW 11 m FM150200 KHz 5351605 KHZ 23002490 KHz frequency 32003400 KHz 39004000 KHz 47505060 KHz 59506200 KHz 71007300 KHz 95009775 KHz 1170011975 KHz 15
12、10015450 KHz 1770017900 KHz 2145021750 KHz 2560026100 KHz 88108 MHzBand division of radio broadcast中波短波120米90米75米短波短波短波60米49米41米短波短波短波31米25米19米短波短波短波16米13米11米调频广播短波短波无线电波的传播1地面传播（地波）2电离层反射（天波）3直射传播（直射波）4散射传播（散射波）5卫星转播长波传播特点是：长波以天波或地波的形式传播。长波地面对它吸收弱，白天和晚上传播，变化较小，比铰稳定。但地波传播的最大距离不超过三至四千公里，所以一般长波传播方式仍以天
13、波为主。短波传播特点是：地面对短波吸收极强，沿地球表短波面只能传播几十公里。它的传播主要是依靠地球外的电离层与地面间的来回反射，因此可以传得很远。由于短波依靠电离层反射，所以受季节、日夜、气候变化影响比较大，信号强弱变化显著，声音常常一会儿大，一会儿小。短波多用于远距离广播。中波传播特点和长波大体相似，但地面对中波吸收中波较强，所以沿地球表面传播路程不远。一般夜里收听效果比白天好，白天收听不到的电台，夜间可能听到。中波适用于传播距离不太远的电台，我国国内广播一般用中波。超短波一般只能在空间直线传播，因此它的门播距超短波离较近，电视和调频广播都用超短波。调幅无线电广播调频无线电广播收音机的主要质
14、量指标1。灵敏度灵敏度说明收音机接收微弱信号的能力。通常用毫伏灵敏度说明收音机接收微弱信号的能力/米（毫伏/米）表示用磁性天线的收音机的灵敏度，用微伏（V）表示装外接天线或拉杆天线的收音机的灵敏度。它们的数值越小，灵敏度越高。2。选择性选择性是表示收音机挑选电台的能力。选择性是表示收音机挑选电台的能力。选择性用分贝（DB）表示，在满足频带宽度的前提下，分贝值越大，选择性越好。3。保真度（失真度保真度失真度）失真度收音机输出的信号波形，应与原来传送的信号一致，保真度表示了收音机保持原来信号波形的能力。保真度表示了收音机保持原来信号波形的能力它主要用频率失真和非线性失真的大小来表示。4。频率范围波
15、段覆盖）频率范围（波段覆盖波段覆盖说明收音机能够收听波段的频率范围，而且在整个波说明收音机能够收听波段的频率范围段范围内应能满足主要指标。5。额定输出功率（不失真输出功率）额定输出功率（不失真输出功率）不失真输出功率表示在一定非线性失真条件下，表示在一定非线性失真条件下，收音机输出功率的大小，通常用毫瓦（MW）或瓦（W）表示，输山功率越大，声音越响。收音机工作原理从工作原理上讲，收音机经过了矿石检波式直接矿石检波式、直接矿石检波式超外差式的转变。放大式和超外差式放大式超外差式矿石式收音机是最简单的收音机，它是由美国科学家邓伍迪和皮卡尔德发明的。1910年，邓伍迪和皮卡尔德发现方铅矿石具有检波作
16、用，如果将其与几种简单的元件相连接，就可以接收到无线电台放送的广播节目。矿石收音机靠天线接收电波，机内装有简单的调谐电路，可将接收到的电波按所需的波长选择出来输送给矿石检波器，The current that records the audio signal is detected from the radio wave, and then the current is converted to sound through the headset. The ore radio needs no batteries, and has a simple structure. Almost all radio enthusiasts can ass
