Antennas Demystified

8/7/2019 Antennas Demystified

http://slidepdf.com/reader/full/antennas-demystified 1/30

Antennas DemystifiedAntennas DemystifiedScott HonakerScott Honaker

N7WLON7WLO



Importance of AntennasImportance of Antennas

Antennas are as important as the radioAntennas are as important as the radio

A $5000 TV with rabbit ears will have a lousy A $5000 TV with rabbit ears will have a lousy

picturepicture Antennas are cheaper than amplifiersAntennas are cheaper than amplifiers

Antennas areAntennas are reciprocal reciprocal ² ² they hear as well as they they hear as well as they

talk talk



Choosing AntennasChoosing Antennas

Frequency Frequency ² ² Dictates sizeDictates size

Mounting locationMounting location ² ² Base or mobileBase or mobile

Omni or directionalOmni or directional ² ² Coverage or gainCoverage or gain PolarizationPolarization ² ² Horizontal, vertical, circularHorizontal, vertical, circular

Resonant or nonResonant or non--resonantresonant ² ² Tuner required?Tuner required?

Power availablePower available

Feedline length and typeFeedline length and type

CostCost



dBi vs. dBddBi vs. dBd

dBidBi -- Gain vs. Isotropic ResonatorGain vs. Isotropic Resonator

Isotropic Resonator is infinitely small antenna withIsotropic Resonator is infinitely small antenna withno feedline in free space radiating equally well in allno feedline in free space radiating equally well in alldirections (spherical pattern)directions (spherical pattern)

dBddBd -- Gain vs. Reference DipoleGain vs. Reference Dipole

Gain referenced to a ´realµ dipole antenna with aGain referenced to a ´realµ dipole antenna with a

donutdonut--like patternlike pattern

dBd = dBi + 2.15 dBdBd = dBi + 2.15 dB



Gain/Loss CalculationsGain/Loss Calculations

ERP ( Effective Radiated Power) is the realERP ( Effective Radiated Power) is the real

number to considernumber to consider

Gain uses a Log Gain uses a Log--10 scale10 scale 3dB = 23dB = 2--fold improvementfold improvement

6dB = 46dB = 4--fold improvementfold improvement



�� ERP=Power x (GainERP=Power x (Gain -- Feedline Loss)Feedline Loss)



R adiation PatternsR adiation Patterns

Visual representation of gain, beamwidth,Visual representation of gain, beamwidth,F/B ratio and F/SF/B ratio and F/Sratio in one planeratio in one plane

EE--Plane is crossPlane is cross--section that includessection that includesdriven elementdriven element

HH--Plane isPlane isperpendicular toperpendicular todriven elementdriven element



Dipole PatternsDipole Patterns



Y agi PatternsY agi Patterns

E-Plane H-Plane



PolarizationPolarization

SSB/CW is generally horizontalSSB/CW is generally horizontal

FM is generally verticalFM is generally vertical

Satellites can be circularSatellites can be circular -- RHCP, LHCPRHCP, LHCP Polarization loss can be significant atPolarization loss can be significant at

VHF/UHF and microwavesVHF/UHF and microwaves

Bounced signals can change polarizationBounced signals can change polarization Verticals are more susceptible to QRMVerticals are more susceptible to QRM



Antenna Design ConsiderationsAntenna Design Considerations

Gain, SWR, Bandwidth, Front/Back ratio areGain, SWR, Bandwidth, Front/Back ratio are

related and optimum values are not achievedrelated and optimum values are not achieved

simultaneously for eachsimultaneously for each

Does antenna have power going in desiredDoes antenna have power going in desired

direction? Gain/Beamwidthdirection? Gain/Beamwidth



SWR Power LossesSWR Power Losses

All power All power fed into the line, minus the linefed into the line, minus the line

attenuation, is absorbed into the load (antenna)attenuation, is absorbed into the load (antenna)

regardless of the mismatch at the antenna terminals regardless of the mismatch at the antenna terminals

Line attenuation (loss) is the key factor inLine attenuation (loss) is the key factor in

determining losses due to mismatched antennasdetermining losses due to mismatched antennas(high SWR)(high SWR)



SWR Loss ExamplesSWR Loss Examples

SWR losses are added to lineSWR losses are added to lineattenuation for total lossattenuation for total lossvaluesvalues

100· RG100· RG--58 @ 20 meters, 50·58 @ 20 meters, 50·RGRG--8x @ 2 meters,8x @ 2 meters,50· Belden 9913 @ 70cm50· Belden 9913 @ 70cmhave nearly identicalhave nearly identicalattenuation of 1.5dBattenuation of 1.5dB

SWR SWR SWR LossesSWR Losses

1.0:11.0:1 0dB0dB

1.5:11.5:1 0dB0dB

2.0:12.0:1 0.2dB or 5%0.2dB or 5%

3.0:13.0:1 0.6dB or 13%0.6dB or 13%

5.0:15.0:1 1.5dB or 29%1.5dB or 29%

10:110:1 3.0dB or 50%3.0dB or 50%



LoadingLoading

Inductive loadsInductive loads ² ² base, center, topbase, center, top

Screwdriver antennas (adjustable loading)Screwdriver antennas (adjustable loading)

Hamstick Hamstick--style antennasstyle antennas

Hustler centerHustler center--loadedloadedwhipswhips

Rubber HT antennasRubber HT antennas

Capacitance ´HatsµCapacitance ´Hatsµ

Texas BugcatcherTexas Bugcatcher

Cushcraft MA5BCushcraft MA5B



Ground Plane VerticalsGround Plane Verticals

¼ wave is omnidirectional with unity (0dBd) gain¼ wave is omnidirectional with unity (0dBd) gainwhen provided a proper ground planewhen provided a proper ground plane

½ wave is unity gain with no ground plane and 3dBd½ wave is unity gain with no ground plane and 3dBd

with ground planewith ground plane 5/8 wave is 3.5dBd gain with nice omni pattern and5/8 wave is 3.5dBd gain with nice omni pattern and

low radiation anglelow radiation angle Longer antennas have more omni patterns withLonger antennas have more omni patterns with

asymmetric ground planes (vehicles) and lowerasymmetric ground planes (vehicles) and lowerradiation angles (see below)radiation angles (see below)

¼ wave ½ wave 5/8 wave



Ground PlanesGround Planes

´Perfectµ ground plane from 120 evenly spaced´Perfectµ ground plane from 120 evenly spaced

radials at least ½ wave in lengthradials at least ½ wave in length

Wire mesh or wire from #12 to #28, above or aWire mesh or wire from #12 to #28, above or afew inches below the ground work finefew inches below the ground work fine

Elevated feeds (1/8Elevated feeds (1/8 or more above ground) canor more above ground) can

use four ¼use four ¼--wave radialswave radials

Vehicles provide poor ground planes at HF butVehicles provide poor ground planes at HF but

elevating the feedpoint reduces losselevating the feedpoint reduces loss



Imperfect Ground PlanesImperfect Ground Planes

Number of radialsNumber of radials 1616 2424 3636 6060 9090 120120

Length of radials inLength of radials in

wavelengthswavelengths

0.10.1 0.1250.125 0.150.15 0.20.2 0.250.25 0.40.4

Total wire installed inTotal wire installed inwavelengthswavelengths

1.61.6 33 5.45.4 1212 22.522.5 4848

Power loss relative toPower loss relative to´perfectµ ground plane´perfectµ ground plane 33 22 1.51.5 11 0.50.5 n/an/a

Feedpoint impedanceFeedpoint impedancein ohmsin ohms

5252 4646 4343 4040 3737 3535



Other VerticalsOther Verticals

DisconeDiscone Wide usable frequency rangeWide usable frequency range

SWR ~2:1 for fundamentalSWR ~2:1 for fundamental

through second harmonicthrough second harmonic SWR ~3:1 for remainder of SWR ~3:1 for remainder of

coveragecoverage

OmnidirectionalOmnidirectional ² ² Unity gainUnity gain

InvertedInverted--LL 22--3 dBd gain with vertical and3 dBd gain with vertical and

horizontal componentshorizontal components

Requires ground planeRequires ground plane



Balanced Feed DesignsBalanced Feed Designs

DipoleDipole

Simple and effectiveSimple and effective

Vertical or horizontal polarizationVertical or horizontal polarization LoopLoop

Full wave has 3dBd gainFull wave has 3dBd gain

Circular, Quad (square) or Delta (triangular) designCircular, Quad (square) or Delta (triangular) design

E and HE and H--plane patterns vary with height aboveplane patterns vary with height above

groundground



Dipole TypesDipole Types

SloperSloper Has 3dB to 6dB of directivity Has 3dB to 6dB of directivity

toward slopetoward slope

InvertedInverted--V V Single high mount, internal angleSingle high mount, internal angle

should be >90 degreesshould be >90 degrees

BentBent

Good attic antennaGood attic antenna Keep center section straightKeep center section straight

Remainder of element can bendRemainder of element can bendor curve to fitor curve to fit



Dipole TypesDipole Types ² ² Cont.Cont.

FoldedFolded

High impedance needsHigh impedance needsopen wire feedopen wire feed

Same overall size as ½ waveSame overall size as ½ wavedipole but contains 1 wave of wire for nearly 3 dBd gaindipole but contains 1 wave of wire for nearly 3 dBd gain

CagedCaged

Standard dipole with each leg made up of multiple wiresStandard dipole with each leg made up of multiple wires

around spacers forming a wire tubearound spacers forming a wire tube Larger effective element diameter increases bandwidthLarger effective element diameter increases bandwidth

Extended Double ZeppExtended Double Zepp

Two 0.64Two 0.64 elements provide 3dBd gainelements provide 3dBd gain



Multiband DipolesMultiband Dipoles

MultipleMultiple Multiple dipoles/loops at a single feedMultiple dipoles/loops at a single feed

TrapTrap Traps are tuned circuits used to generate multipleTraps are tuned circuits used to generate multiple

resonances on a single wireresonances on a single wire

Traps cause loss and decrease bandwidthTraps cause loss and decrease bandwidth

G5RV G5RV NonNon--resonantresonant ² ² tuner requiredtuner required

Radiation patterns vary with frequency Radiation patterns vary with frequency



Off Off--Center Fed DipolesCenter Fed Dipoles

Feedline attached 1/3 the length from the endFeedline attached 1/3 the length from the end

Same ½ wave overall sizeSame ½ wave overall size

Resonates at even harmonics, so 1 antenna can beResonates at even harmonics, so 1 antenna can beused on 80m, 40m and 20mused on 80m, 40m and 20m

66thth harmonic (15m) has too high impedanceharmonic (15m) has too high impedance

Asymmetric impedance may cause current ´in theAsymmetric impedance may cause current ´in the

shackµshackµ Requires 4:1 or 6:1 currentRequires 4:1 or 6:1 current--type balun to matchtype balun to match



OtherMultibandersOtherMultibanders

Random wireRandom wire

Can be any length of wireCan be any length of wire

Requires tunerRequires tuner Works against earth groundWorks against earth ground

WindomWindom

´Tµ shape single wire feed attached 14% off center´Tµ shape single wire feed attached 14% off center

Works against earth groundWorks against earth ground

´R F in the shackµ is a potential problem´R F in the shackµ is a potential problem



Wire ArraysWire Arrays

Half SquareHalf Square

Vertical polarization with up to 3.8dBd gainVertical polarization with up to 3.8dBd gain

BiBi--squaresquare

Horizontal polarization with ~3.5dBd gainHorizontal polarization with ~3.5dBd gain

Bobtail CurtainBobtail Curtain

Vertical polarization with bidirectional 5.8 dBd gainVertical polarization with bidirectional 5.8 dBd gain

Sterba CurtainSterba Curtain Horizontal polarization from multiple phased loopsHorizontal polarization from multiple phased loops

Lazy ´HµLazy ´Hµ ² ² Four element broadside array Four element broadside array

Greater than 6dBd gain possibleGreater than 6dBd gain possible



Y agisY agis

½ wave dipole driven element½ wave dipole driven element

Reflectors are 5% largerReflectors are 5% larger

Directors are 5% smallerDirectors are 5% smaller Number of elements and boom lengthNumber of elements and boom length

determine gaindetermine gain

SWR, bandwidth, gain, boom length andSWR, bandwidth, gain, boom length andfront/back ratios all have to be consideredfront/back ratios all have to be considered



Typical Y agi GainsTypical Y agi Gains

10m yagi with10m yagi withSWR <2:1 andSWR <2:1 andFront/Back Front/Back

>20dB>20dB Numbers areNumbers are

rounded torounded tonearest 0.5 dBnearest 0.5 dB

ElementsElements Gain dBiGain dBi Gain dBdGain dBd

33 7.57.5 5.55.5

44 8.58.5 6.56.555 1010 88

66 11.511.5 9.59.5

77 12.512.5 10.510.588 13.513.5 11.511.5



Hybrid Y agisHybrid Y agis

QuadQuad 11 loop driven element, reflector and directorsloop driven element, reflector and directors

Up to 3dBd gain over standard yagiUp to 3dBd gain over standard yagi

Wider bandwidth than standard yagiWider bandwidth than standard yagi

QuagiQuagi Loop reflector and driven elementLoop reflector and driven element

Simpler to feed and match at UHFSimpler to feed and match at UHF LooperLooper

Entirely loop (generally circular) elementsEntirely loop (generally circular) elements



Log PeriodicLog Periodic

Constant characteristics overConstant characteristics overwide band (2:1)wide band (2:1)

Several varieties but hamsSeveral varieties but hams

generally use dipole array generally use dipole array (LPDA)(LPDA)

All elements are drivenAll elements are driven

Gain similar to 3 elementGain similar to 3 elementyagiyagi ² ² 7dBi, 5dBd7dBi, 5dBd

Size similar to 3 elementSize similar to 3 elementyagi at lowest frequency yagi at lowest frequency



R eflecting AntennasR eflecting Antennas

Corner reflectorCorner reflector Practical size at 222 MHz and upPractical size at 222 MHz and up

Simple to construct, broadbanded, gains 10Simple to construct, broadbanded, gains 10--15dBd15dBd

Pyramidal HornPyramidal Horn Practical at 902 MHz and upPractical at 902 MHz and up

Sides of horn are fed for up to 15 dBi, 13dBd gainSides of horn are fed for up to 15 dBi, 13dBd gain

Parabolic dishParabolic dish Gain is a function of reflector diameter, surfaceGain is a function of reflector diameter, surface

accuracy and illuminationaccuracy and illumination



Parabolic Dish GainParabolic Dish Gain

MHzMHz 2·2· 4·4· 6·6· 10·10· 20·20· 30·30·

420420 6.0dBi6.0dBi 12.012.0 15.515.5 20.020.0 26.026.0 29.529.5

902902 12.512.5 18.518.5 22.022.0 26.526.5 32.532.5 36.036.012151215 15.015.0 21.021.0 24.524.5 29.029.0 35.035.0 38.538.5

23002300 20.520.5 26.526.5 30.030.0 34.534.5 40.540.5 44.044.0

33003300 24.024.0 30.030.0 33.533.5 37.537.5 41.541.5 47.547.556505650 28.528.5 34.534.5 38.038.0 42.542.5 46.046.0 52.052.0

10Ghz10Ghz 33.533.5 39.539.5 43.043.0 47.547.5 51.051.0 57.057.0

Antennas Demystified

Documents

Transcript of Antennas Demystified

Destructuring demystified

Trigonometry Demystified

ɷIv therapy demystified (demystified nursing)

index-of.co.ukindex-of.co.uk/Misc/McGraw-Hill - Trigonometry Demystified.pdf · TRIGONOMETRY DEMYSTIFIED . TRIGONOMETRY DEMYSTIFIED . ... ALGEBRA DEMYSTIFIED Rhonda Huettenmuller

ERP Demystified

Bluetooth Demystified

vsam demystified

Meta Demystified

German Conversation DemystifiedPharmacology Demystified Physics Demystified Physiology Demystified Pre-Algebra Demystified Precalculus Demystified Probability Demystified Project Management

Demystified Series · Statistics Demystified String Theory Demystified Technical Analysis Demystified Technical Math Demystified Trigonometry Demystified Vitamins and Minerals Demystified.

Decorators demystified

Automation Demystified

PDU Demystified

Demystified Series - stringworld.rustringworld.ru/files/McMahon_D._String_theory_demystified.pdf · Demystified Series Accounting Demystified Advanced Calculus Demystified Advanced

Webfonts: Demystified

WebRTC Demystified

IPG Demystified

SEO Demystified

Postgres demystified

AdvancedCalculus - cloudflare-ipfs.com...AS P.NET 2.0 Demystified Aslronomy Demystified Audio Demystified Biology Demystified Biotechnology Demystified Business Calculus Demystified