Sökning: "HF radio"

Visar resultat 1 - 5 av 8 avhandlingar innehållade orden HF radio.

  1. 1. Power and frequency assignment in HF Radio Networks

    Författare :Dag Stranneby; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; HF-radio networks; radio data networks; frequency assignment; power control; artificial neural networks; Information technology; Informationsteknik; SRA - ICT; SRA - Informations- och kommunikationsteknik;

    Sammanfattning : .... LÄS MER

  3. 2. Radio waves in the ionosphere : Propagation, generation and detection

    Författare :Tobia Carozzi; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Astronomy; Astronomi; Astronomy and astrophysics; Astronomi och astrofysik; Space Physics; rymdfysik;

    Sammanfattning : We discuss various topics concerning the propagation, generation, and detec-tionof high-frequency (HF) radio waves in the Earth's ionosphere. With re-gardsto propagation, we derive a full wave Hamiltonian and a polarization evo-lutionequation for electromagnetic waves in a cold, stratified magnetoplasma. LÄS MER

  4. 3. Secondary Electromagnetic Radiation Generated by HF Pumping of the Ionosphere

    Författare :Lars Norin; Bo Thidé; Savely M. Grach; Bengt Gustafsson; James W. LaBelle; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; space physics; ionospheric modification experiments; plasma turbulence; stimulated electromagnetic emission; ionospheric irregularities; radio waves; parametric processes; thermal parametric instability; transient dynamics; wave-wave interactions; Physics; Fysik;

    Sammanfattning : Electromagnetic waves can be used to transmit information over long distances and are therefore often employed for communication purposes. The electromagnetic waves are reflected off material objects on their paths and interact with the medium through which they propagate. LÄS MER

  5. 4. Opening New Radio Windows and Bending Twisted Beams

    Författare :Erik Nordblad; Thomas B. Leyser; Kristof Stasiewicz; Vladimir Pavlenko; Paul A. Bernhardt; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Orbital angular momentum; Hall effect; Nonparaxial beam; Geometrical optics; High frequency radio waves; Ray tracing; Magnetic zenith effect; Ionospheric irregularities; Wave propagation; Fysik med inriktning mot rymd- och plasmafysik; Physics with specialization in Space and Plasma Physics;

    Sammanfattning : In ground based high frequency (HF) radio pumping experiments, absorption of ordinary (O) mode pump waves energises the ionospheric plasma, producing optical emissions and other effects. Pump-induced or natural kilometre-scale field-aligned density depletions are believed to play a role in self-focussing phenomena such as the magnetic zenith (MZ) effect, i. LÄS MER

  7. 5. The Auroral Large Imaging System : design, operation and scientific results

    Författare :Urban Brändström; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Space and plasma physics; Aurora; Artificial airglow; HF-pump enhanced airglow; Multistation measurements; Polar Stratospheric clouds; Radio-Induced optical emissions; Spectroscopic imaging observations; Tomography; Rymd- och plasmafysik; Space physics; Rymdfysik; rymdfysik; Space Physics;

    Sammanfattning : The Auroral Large Imaging System (ALIS) was proposed in 1989 by Åke Steen as a joint Scandinavian ground-based nework of automated auroral imaging stations. The primary scientic objective was in the field of auroral physics, but it was soon realised that ALIS could be used in other fields, for example, studies of Polar Stratospheric Clouds (PSC), meteors, as well as other atmospheric phenomena. LÄS MER