Path: utzoo!mnetor!uunet!husc6!mit-eddie!ll-xn!adelie!infinet!rhorn From: rhorn@infinet.UUCP (Rob Horn) Newsgroups: comp.protocols.tcp-ip Subject: Re: Ethers, Copper, Fiber, Microwaves, Etc. Message-ID: <1045@infinet.UUCP> Date: 12 Dec 87 18:55:45 GMT References: <16836@bu-cs.BU.EDU> <8712101810.AA00864@PTT.LCS.MIT.EDU> Reply-To: rhorn@infinet.UUCP (Rob Horn) Organization: Infinet, Inc. North Andover, MA Lines: 30 I think that these systems are operating in the 23 GHz band. The frequencies between 21.2 and 23.6 GHz are set aside for commercial short-haul communications. This band has 2.4 GHz available, which is a whole lot. The equipment also tends to be relatively cheap, typically under $50K. The antennas that I have seen have been 2-3 foot diameter, giving antenna beam widths of a few degrees. This is more suitcase size than briefcase size. The wider beam width and small antenna make these easy to install. The reliable range at 23 GHz is at most a few miles. The attenuation in air is not too bad, but fog and rain cause significant problems. You have to expect dropouts during heavy rains. The greater the distance, the more you need to worry about these things. Short-haul microwave is a good complement to fiber optic and copper wiring. The installation cost is much lower than physical cable, provided you have line of site between the two ends. FCC licensing is required but usually easy to get. The frequency band is huge, not too heavily used (yet), and the attenuation is such that you can ignore sites that are many miles away. You have to put up with dropouts during heavy rains, so for applications that must work during bad weather they are a bad choice. (Dropouts act like a very overloaded gateway. Traffic can still pass occasionally but lots of packets get lost.) -- Rob Horn UUCP: ...harvard!adelie!infinet!rhorn Snail: Infinet, 40 High St., North Andover, MA (Note: harvard!infinet path is in maps but not working yet)