Foundation Licence Feeders and Antennas

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.

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

Types of Plug BNC Plug PL 259 Plug

Types of Antenna

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

The Half – Wave Dipole half wavelength Transceiver dipole

¼ Antenna Coax Feed

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

The Yagi Antenna

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

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

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

Matching Antennas / Feeders Source of Energy Load

Matching Antennas Source of Energy Load Energy reflected back to source

SWR: Standing Wave Ratio How good a match?

You don’t have to know this yet! But…

Antenna Tuning Unit (ATU)

SWR Meter

Variation of SWR with Dipole Length

Dummy Loads

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

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

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