The Science Forum - Scientific Discussion and Debate
		Live Chat    FAQ    Search    Usergroups
	Register  ::  Log in	Log in to check your private messages
	Science Forum Forum Index » Electronics » Transmitter range  Transmitter range « View previous topic :: View next topic »  Author Message harvestein Posted: Mon Feb 18, 2008 6:52 am    Post subject: Transmitter range Forum Freshman Joined: 18 Feb 2008 Posts: 45 Does anyone know the general rule that defines transmitter range? i know it varies massively dpending on location, height, power, aerial type etc. But whats the general rules for good performance? is there a power/distance equation? Im experimenting with some circuits in the CB band, but im clueless when it comes to aerials, besides impediance matching. Back to top Pumblechook Posted: Wed Feb 20, 2008 12:28 pm    Post subject: Forum Freshman Joined: 05 Dec 2007 Posts: 53 It is quite a complex subject really. There are path loss calculators on-line but these assume a line-of-sight path. 27 MHz CB does not propagate well even over short distances. It does open up from time to time either very long distance. (e.g .transatlantic) via F layer ionosphere or shorter Sporadic E layer (Europe). But for normal commnmications beyond 30 miles it tends to be poor. Low VHF is better and higher VHF is better still for comms up to 100 - 300 km under normal conditions. Troposcatter and tropo bending are always present to some extent at VHF (70 MHz and higher) and UHF and ducting at times of high atmos pressure can extend the range to a 1000 km or more. Receivers can work down to incredibly low levels of signal but there is a limit when receiver noise and external noise or interference masks the signal. Think of a lamp sending out light in all directions. At some distance r away from the lamp the light will cover the inner surface of an imaginary sphere of radius r. The surface area of the sphere is 4 pi r2 (r sqrd). So the power per sq metre is inversely proportional to the square of the distance. At 1 km you will get X picowatts/sq m at 2 km it will drop to X/4 at 10 km it will drop to X/100. Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First     Page 1 of 1 Science Forum Forum Index » Electronics » Transmitter range Jump to: Select a forum Natural Sciences----------------Astronomy & CosmologyBiologyChemistryEarth SciencesMathematicsPhysics People----------------Behavioral & Social SciencesHealth & MedicinePhilosophical DiscussionHistoryReligionPoliticsCriminology and Forensic Science General Technology----------------Computer ScienceElectronicsMilitary Technology Information Technology----------------Business & EconomicsEducationEngineering & Transportation International Issues----------------Environmental IssuesIn the News The Science Forum----------------General DiscussionIntroductionsScience-Fiction and Non-FictionExperimentationPseudoscienceLinksArt and Culture Site Administration----------------Site FeedbackTrash Can  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum
	Enter your search terms Submit search form   Web www.thescienceforum.com © 2004-2008 Thescienceforum.com Sponsored by EnluxLED Partner Forums Politics Forum  Radar Detector