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podcast:ddop:public:episode_201906

Episode 2019-06 - Antenna and Radio Wave Basics

Hello and welcome to the next edition of the Mike Wills Podcast! This is the Dog Days of Podcasting edition for August 6th, 2019. I am WX0MIK and my name is Mike Wills. This season, we are covering amateur (or ham) radio.

Notes

  • Antenna and Radio Wave Basics
  • An antenna can any type of conductor: a wire, rod, pipe, tape measure, metal coat hanger, any type of conductor
  • The key is it must match a fraction of the signal's wavelength. Typically 1/2 wave, but there are others including 1/4 and 5/8.
  • A radio wave contains both electrical and magnetic energy which oscillate as the same frequency as the RF current in the antenna.
  • Polarization refers to the orientation of the radio waves electric field.
    • For most handheld/mobile operation requires vertical polarization.
    • For HF, polarization doesn't matter because the ionosphere changes the polarization.
    • For transmissions from space, the polarization is typically circular. My SSTV transmission from the ISS worked only if I held the antenna horizontally.
  • A feed line is used to deliver the radio signals to and from the antenna.
  • The book also introduces impedance of the feed line and how that affects transmissions.
  • Antenna Gain
    • What is gain? Radiated signals in a specific direction.
    • An antenna creates gain by radiation radio waves that add together in the preferred direction and cancel in others.
    • All antennas are measured in DBi, that is as compared to an isotropic antenna which radiates in all directions equally in all directions. This is impossible.
    • A beam or directional antenna focuses the signal in one direction
    • Radiation Patterns
  • Decibels - The decibel measures the ratio of two quantities as a power of 10. This can get confusing.

Wrap Up

Thank you for listening. 73 from WX0MIK. The frequency is clear.

Contact Information

podcast/ddop/public/episode_201906.txt · Last modified: 2019/08/07 03:08 by mikewills