Propagation -- Radio signal propagation
About Propagation	English (USA)
Welcome to the 'Propagation' e-mail reflector (an opt-in-subscription e-mail 'mailing' list, free-of-charge). This is a discussion 'group' primarily focused on the science of getting a radio signal from one location to another. The main focus is the long distance (DX) propagation of shortwave radio signals. However, it is also acceptable to discuss propagation of longwave, mediumwave, as well as VHF and above radio signals. This discussion list is available and accessible to any person who is interested in exchanging ideas, and discussing the propagation of radio waves. Included are the topical areas of space weather (and the affect on radio propagation), ionospheric science, geomagnetic science, and to some degree, weather phenomenon as it may affect the propagation of radio wave. Radio propagation is the behavior of radio waves when they are transmitted, or propagated from one point on the Earth to another, or into various parts of the atmosphere. Like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization and scattering. Radio propagation is affected by the daily changes of water vapor in the troposphere and ionization in the upper atmosphere, due to the Sun. Understanding the effects of varying conditions on radio propagation has many practical applications, from choosing frequencies for international shortwave broadcasters, to designing reliable mobile telephone systems, to radio navigation, to operation of radar systems. Radio propagation is also affected by several other factors determined by its path from point to point. This path can be a direct line of sight path or an over-the-horizon path aided by refraction in the ionosphere. Factors influencing ionospheric radio signal propagation can include sporadic-E, spread-F, solar flares, geomagnetic storms, ionospheric layer tilts, and solar proton events. Radio waves at different frequencies propagate in different ways. The interaction of radio waves with the ionized regions of the atmosphere makes radio propagation more complex to predict and analyze than in free space. Ionospheric radio propagation has a strong connection to space weather. A sudden ionospheric disturbance or shortwave fadeout is observed when the x-rays associated with a solar flare ionize the ionospheric D-region. Enhanced ionization in that region increases the absorption of radio signals passing through it. During the strongest solar x-ray flares, complete absorption of virtually all ionospherically propagated radio signals in the sunlit hemisphere can occur. These solar flares can disrupt HF radio propagation and affect GPS accuracy. On-topic posts to this e-mail reflector include detailed reports and summaries of past and current solar (space weather) and geophysical (geomagnetic) events, as well as forecasts of space and geophysical weather as related to radio signal propagation and for establishing communication circuits. Additionally, it is acceptable to discuss reports of station-to-station conditions and analysis, contest results that reveal propagation conditions, discussions of antennas and related propagation topics involving antenna engineering, and transmission modes, noise, and so on. Some reference sites: ARRL Propagation Page The American Radio Relay League (ARRL) page on radio propagation. HF Radio and Ionospheric Prediction Service - Australia NASA Space Weather Action Center HF Propagation Tutorial by the late NM7M Space Weather and Radio Propagation Resource Center Live data and images of space weather and radio propagation. High Frequency radio propagation de-mystified. Is High Frequency radio propagation reciprocal? How does noise affect radio signals? Please do not post questions about general topics like equipment wanted and/or for sale, e-mail addresses needed, DX QSL routes, and so forth. NOTE: DO NOT USE THIS REFLECTOR TO POST COMPLAINTS, PERSONAL CRITICISMS, ATTACKS, ETC AGAINST OTHER LIST MEMBERS. VIOLATORS OF THIS POLICY WILL BE REMOVED IMMEDIATELY WITHOUT NOTICE. HOWEVER: this is a somewhat scientific forum, and therefore is available for the exchange of ideas, as well as the challenge by interested individuals of current ideas, new theories, and the critical examination of data and the interpretation of that data. EXPECT PEER-REVIEW of your science! Above all, be considerate of all other subscribers, both in your tone, your tact, as well as be considerate of those who have bandwidth limitations, in which case please edit your replies by removing any text that is not needed to give reference to your response (in other words, only quote the very minimum that is needed for clarity). Whether you are a beginner, or an expert, we all welcome you, and encourage you to participate by asking questions on radio signal propagation, space weather, and by submitting your ideas, insights, and reports. Thank you for joining in. -- the Moderator, Tomas Hood (NW7US) http://sunspotwatch.com/ To see the collection of prior postings to the list, visit the Propagation Archives. (The current archive is only available to the list members.) Also check out the searchable archives.
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