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This guide explores the core functions of feeders and antennas in radio communication systems. Feeders transfer RF current from transceivers to antennas without radiating waves, while antennas efficiently convert RF energy into waves. We delve into different types of feeders like coaxial cables and ribbon feeders, as well as antenna designs such as the half-wave dipole, Yagi, and ground planes. Key concepts include SWR (Standing Wave Ratio), effective radiated power, and balancing techniques using devices like Baluns and Antenna Tuning Units (ATUs).

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Foundation Licence

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  1. Foundation Licence Feeders and Antennas

  2. What they do Feeder: transfers RF current between a transceiver and antenna without radiating radio waves. (Hope springs eternal). Antenna: transfers RF energy with best possible efficiency from RF current to RF wave or from RF wave to RF current.

  3. Types of Feeder Ribbon Feeder Coaxial Cable (coax) Open Wire Feeder

  4. Types of Plug PL 259 Plug BNC Plug

  5. Types of Antenna

  6. Half Wave Dipole ¼ Wave ground plane 5/8 ground plane Yagi antenna End fed wire. At Foundation Level:

  7. half wavelength dipole Transceiver The Half – Wave Dipole

  8. Coax Feed ¼Antenna

  9. 5/8  Antenna • Improved low angle radiation pattern • Has ‘gain’ (4dB) • Coil: for matching to transmitter (adds 1/8  )

  10. The Yagi Antenna

  11. 3dB 6dB 9dB 10dB 2 times 4 times 8 times 10 times Ways of indicating “Gain”

  12. Effective Radiated Power (erp) erp = antenna gain × transmit power

  13. Polarisation Vertical Polarisation Horizontal Polarisation Direction of Polarisation is the same as the direction of electric field.

  14. Matching Antennas / Feeders Source of Energy Load

  15. Matching Antennas Energy reflected back to source Source of Energy Load

  16. SWR: Standing Wave Ratio How good a match?

  17. You don’t have to know this yet! But…

  18. Antenna Tuning Unit (ATU)

  19. SWR Meter

  20. Variation of SWR with Dipole Length

  21. Dummy Loads

  22. It’s all a matter of balance Balance = electrical symmetry

  23. The Balun Retains the electrical symmetry of a balanced antenna if we connect it to an unbalanced feeder.

  24. Dipole Antenna (Balanced) Balun Coaxial cable feeder (unbalanced)

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