文摘This paper attempts to provide some insight into the nature of radio propagation in that part of the spectrum (upper VHF to microwave) used by experimenters for high-speed digital transmission. 本文试图提供一些深入的无线电传播的本质中这一部分的频谱(上部甚高频微波)使用高速数字传输实验人员。It begins with the basics of free space path loss calculations, and then considers the effects of refraction, diffraction and reflections on the path loss of Line of Sight (LOS) links. 它开始于基本的自由空间路径损耗的计算,然后考虑折射的影响、衍射、反思的路径损耗的视线(LOS)链接。The nature of non-LOS radio links is then examined, and propagation effects other than path loss which are important in digital transmission are also described.non-LOS无线链路的本质是然后检查,其他的作用和传播路径损耗这很重要,数字传输也进行了描述。 Introduction介绍The nature of packet radio is changing. 小包收音机的性质正在发生变化。As access to the Internet becomes cheaper and faster, and the applications offered on the net more and more enticing, interest in the amateur packet radio network which grew up in the 1980s steadily wanes. 访问互联网变得更快、更便宜,而应用程序提供的“净”更多,更吸引人,兴趣业余无线电网络数据包成长于1980年代逐步减弱。To be sure, there are still pockets of interest in some places, particularly where some infrastructure to support speeds of 9600 bps or more has been built up, but this has not reversed the trend of declining interest and participation. 可以肯定的是,还有人的钱包在一些地方,尤其是在一些基础设施,以支持时速为9600个基点以上建立起来了,但是这并没有扭转趋势下降的兴趣和参与。Nevertheless, there is still lots of interest in packet radio out there - it is simply becoming re-focused in different areas. 然而,仍然有很多兴趣分组无线它仅仅是在不同的地区变得严格。Some applications which do not require high speed, and can take advantage of the mobility that packet radio can provide, have found a secure niche - APRS is a good example. 有些应用程序不需要高速度,并可以利用机动性,小包收音机可以提供,找到了一个安全的位置APRS就是一个很好的例子。Interest is also high in high-speed wireless transmission which can match, or preferably exceed, landline modem rates. 利息也有很高的高速无线传输可以匹配,或者最好超过、有线调制解调器率。With a wireless link, you can have a 24-hour network connection without the need for a dedicated line, and you may also have the possibility of portable or mobile operation. 与一个无线连接,你可以有一个24小时的网络连接,而不需要使用专用线路,你或许也有可能性的便携式或移动操作。Until recently, most people have considered it to be just too difficult to do high-speed digital. 直到最近,大多数人都认为它非常难做高速数字。For example, the WA4DSY 56 Kbps RF modem has been available for ten years now, and yet only a few hundred people at most have put one on the air. 例如,WA4DSY 56 Kbps射频现代已有十年,然而现在只有几百人在大多数都把一个放在空气。With the new version of the modem introduced last year, 56 Kbps packet radio has edged closer to plug n play, but in the meantime, landline modem data rates have moved into the same territory. 与新版本的调制解调器在去年推出的56 Kbps包广播已经更加接近堵塞的氮发挥,但与此同时,许多有线调制解调器的数据速率已经进入相同的境地。What has really sparked interest in high-speed packet radio lately is not the amateur packet equipment, but the boom in spread spectrum (SS) wireless LAN (WLAN) hardware which can be used without a licence in some of the ISM bands. 真正的兴趣在高速分组无线最近不是业余包设备,但繁荣的扩频(SS)无线局域网(WLAN)硬件可以使用无证在一些ISM的乐队。The new WLAN units are typically integrated radio/modem/computer interfaces which mimic either ethernet interfaces or landline modems, and are just as easy to set up. 新的WLAN单位通常集成无线/现代/计算机接口模拟要么以太网接口或有线调制解调器,也同样容易设置。Many of them offer speeds which landline modem users can only dream of. 很多提供有线调制解调器速度,用户只能梦想。TAPR and others are working on bringing this type of SS technology into the amateur service, where it can be used on different bands, and without the Effective Radiated Power (ERP) restrictions which exist for the unlicenced service. TAPR和其他公司正致力于将这种类型的SS技术到业余服务,在那里可以用于在不同的乐队,又没有有效辐射功率(ERP)的限制而存在unlicenced服务。This technology will be the ticket to developing high-speed wireless LANs and MANs which, using the Internet as a backbone, could finally realize the dream of a high-performance wide-area AMPRnet which can support the applications (WWW, audio and video conferencing, etc.) that get people excited about computer networking these days.这项技术将会成为机票发展高速无线局域网和芒,使用互联网作为骨干,终于可以实现梦想的高性能广域AMPRnet可以支持应用程序(WWW、音频和视频会议等),让人们兴奋这些天电脑网络。Although the dream as stated above is somewhat controversial, the author believes it represents the best hope of attracting new people to the hobby, providing a basis for experimentation and training in state-of-the-art wireless techniques and networking, and, ultimately, retaining spectrum for the amateur radio service. 虽然梦想是像上面说的是有点争议的,作者认为它代表了最佳希望吸引新人们的喜好提供依据实验和培训在最先进的无线技术和网络,最终保留业馀无线电频谱服务。One problem is that most of the people attracted to using digital wireless techniques have little or no background in RF. 一个问题是,大部分的人吸引到使用数字无线技术有很少或没有背景在射频(RF)。When it comes to setting up wireless links which will work over some distance, they tend to lack the necessary knowledge about antennas, transmission lines and, especially, the subtleties of radio propagation. 当涉及到建立无线连接将工作有一段距离,他们往往缺乏必要的知识对天线、输电线路,尤其是无线电传播的微妙之处。This paper deals with the latter area, in the hopes of providing this new crop of digital experimenters with some tools to help them build wireless links wh