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Types of Antennas

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TYPES of ANTENNASECE 414Transmission lines and Antennas

I. Basic Practical AntennasHalf Wave Dipole- considered the simplest and most practical antenna- center fed- it is a simple wire composed of two tuned segments- balanced

Radiation Pattern : BidirectionalRadiation Resistance : 73 ohms at the feed pointEffective length : /2Effective height : /Effective Area : 0.13 Gain : 1.64 or 2.15 dBApplication:AM, CBLength with end-effect:(0.95) /2

I. Basic Practical Antennas2. Half Wave Folded Dipole- basically a dipole that has been folded back upon itself- with higher Bandwidth and input impedance compared to an ordinary dipole

Radiation Pattern : Bidirectional Input impedance: 300 ohmsEffective length : /2Effective height : /Effective Area : 0.13 Gain : 1.64 or 2.15 dBApplication:incorporated in another RF antenna design with other elements nearby.Length with end-effect:(0.95) /2

I. Basic Practical Antennas2. Half Wave Folded Dipole

I. Basic Practical Antennas3. Turnstile Antenna- a variation of the half wave dipole- its is 2 dipoles antenna aligned at 90- with circular polarization when mounted vertically

Radiation Pattern : omnidirectional when horizontally installedPolarization:CircularInput impedance: approx 36 ohmsGain : 2.15 dBiSWR: 1.44Application:Tele Communication satellites

I. Basic Practical Antennas3. Turnstile Antenna

I. Basic Practical Antennas4. Marconi Antenna- a grounded quarter wave vertical antenna commonly used in AM broadcasting- uses groundwave propagation that uses the earth ofr its conductivity- element length is and can be doubled by a mirror image due to ground- used as alternative to dipole-not applicable to fry areas

Radiation Pattern : omnidirectional on the horizontal planePolarization:CircularInput impedance: 37 ohms at the feedEffective length : / Gain : 2.15 dBiSWR: 1.44Application:AM

I. Basic Practical Antennas5. Groundplane Antenna- a quarterwave vertical radiator with four radials that simulate ground for the radiator- it is a general purpose antenna useful from HF through UHF

Radiation Pattern : non directionalPolarization:VerticalInput impedance: 50 ohms at the feedRadial Droop Angle:30 to 45Gain : 0 dBVSWR: 1.5Application:RF Scanners, CB amateur FM and ATV uses

II. The Space Limited AntennasInvisible AntennasClothesline antennaRain gutter antennaFlagpole antenna2. Indoor antenna 3. Loaded antenna

III. The Long Wire and Travelling Wave AntennasLong wire antenna simply a long piece of wire that is used as an antenna-can be used in any frequency band-used by many armies in the world Travelling wave antenna is terminated by a resistance matching its characteristic impedance so no standing wave is presentLong single wire antenna is a wire antenna with several wavelength long and fed at a current loop or at one end.The V Beam antenna is constructed with two long wires combined to form a V with an angle that is twice that of the major lobes of the wires excited out of phaseRadiation Pattern (unterminated) Bidirectional(terminated end) UnidirectionalInput Impedance: 300 to 450 Ohms

III. The Long Wire and Travelling Wave Antennas3. The rhombic antenna is a large wire antenna, shaped vaguely like a diamond or rhombus- It is a broadband traveling wave antenna used for skywave (HF) communications

III. The Long Wire and Travelling Wave AntennasRadiation pattern:UnidirectionalPolarization : HorizontalInput Impedance 650 700 ohmsRadiation angle : 40 75 degrees Main disadvantage : Requires large land area

III. The Long Wire and Travelling Wave Antennas4. Fishbone antenna it is equivalent to two antennas stacked vertically

IV. The Loop AntennaLoop antenna is basically a loop of conductive material which could be resonant at or near the desired frequency. It can be made of wire or metal hoops. Have continuous conducting path leading from one conductor of a two wire transmission line to the other conductorPopular uses are for Dxing (Direction finding)

The large loop similar to a dipole except that the ends of the dipole are connected to form a circle, a triangle (delta loop), or square. - Usually is at half wave or one wavelength in circumference- the large loop has its strongest signal in the plane of the loop and nulls at the axis perpendicular to the plane of the loop.- a circular loop gets a higher gain, and are more immune to localized noise .

IV. The Loop Antenna2. The small Loop also called the magnetic loop antenna is a loop of wire less than a wavelength in circumferenceThis antenna detects the magnetic component of the electromagnetic waveMaximum radiation or reception normal-perpendicular to the plane of the loop.

IV. The Loop Antenna