VE3KL Selecting a Portable HF Antenna

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VE3KL Selecting a Portable HF Antenna

• Basic Issues
• Ease of operation Mechanical Design(weight ..
• Efficiencyminimum gain around 3dBi a goal.
• Antenna patterns.. Some are quite directive
• Ease of matching. Very important
• Transmission Line Losses

Sotabeams Trap
4nec2 Simulator
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Presentation Outline

• Problem Definition
• Typical Portable Antennas
• Transmission Line TypesHow to select
• Case Studies
• Conclusion

James Clerk Maxwell
Georg Simon Ohm
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Types of Portable Operation

• Summits On The Air (SOTA). Extreme
• Pedestrian Portable. Very specialized
• Casual outings in a park
• Weekend camping.. Dual band plus VHF
• Field Day More seriousneed performance
• Portable Operation from a vehicle..
• ..

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Antenna Classification(for spotting good DX
designs, not NVIS)

• Big antennas that are mounted well off the
  ground ?/4
  High Gain at 30 Deg Elevation
  
• Small and/or near ground antennas Low
  Gain at 30 Deg Elevation
  

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Antenna Classification(Base Numbers.No
Losses, Perfect Ground)30 Degree Elevation
Angle

• Halfwave Dipole, 14 MHz, 30 deg.elev.
  7m High, Horizontal 5.5 dBi Max Gain
• Vertical Antennas, Length ?/4
  3.5 dBi Max Gain

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Typical Antenna30, 17 Metres Trapped Inverted
VPerformance?
Mini Toroid Trap VE3KL Design
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Antenna Photo CollageSource SOTA/Hfpack
Diamond
http//www.bing.com/images/search?qsotaantennas
qpvtsotaantennasqpvtsotaantennasFORMIGRE
http//hfpack.com/moderators/n0vz
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Some Antenna Candidates

• Inverted V. Monoband
• Trapped Inverted V. Multi band
• Inverted L Monoband with One Radial (SOTA)
• Quarter Wave Ground Plane four radials above
  ground
• Rotating monoband dipole
• Pedestrian Verticalone insulated radial
• Random Wire, End Fed, Small/Big Loops, Diamond

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Some Antenna CandidatesDiamond Shape

Apex Angle
Trap or Loading Coil
Base near ground
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System Simulation Includes

• Cable Skin Effect
• Cable Dielectric Loss
• Cable Internal and External Inductance
• Cable DC Resistance
• Cable Velocity Factor
• Antenna Wire Loss (Copper or Al)
• Antenna Wire Insulation ( Dielectric, not losses)
• Antenna Ground Type (Average)
• Trap and Loading Coil Loss..Q 100 for all cases

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Transmission Line Selection

• Loss not too important (Short Lines Used)
• Light weight
• Easy to use
• Coax preferred. Open wire hard to use

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Transmission Line Selection
RG-58U 10m long 0.5 dB Loss 14 MHz (Belden 8219)
Recommended
RG-8X 10 m long 0.36 dB Loss 14 MHz (Belden
9258) Recommended

Approx Skin Effect Limited 0.1 MHz and above
Skin Effect Limited 1 MHz and above
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Transmission Line Selection
RG174 U 10m long 1.1 dB Loss 14 MHz (Belden
8216) Poor
RG174 U 10 m long 0.84 dB Loss 14 MHz
(Belden 7805) OK ???

Skin Effect Limited 1 MHz and above
Skin Effect Limited 1 MHz and above
Approx Skin Depth Limited Above 20 MHz Very High
Loss at 100 MHz
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Case Studies

• Full Size Dipole..20 Metres
• Trapped Inverted V...30 and 17 Metres
• Sota Inverted L...20 Metres
• Hamstick/Buddipole Type Dipole...20 Metres
• Vertical Diamond...20 Metres
• Pedestrian Vertical...20 Metres
• Short Vertical_Four Low Radials...20 Metres

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Al Tubing
Case Study 1Full Size Dipole 14 MHzJust
Manageable in Moderate Wind
Height 7 metres AL Telescoping Tubing Light
Balun 11 at top Light mast guy ropes RG8X 0.4
dB loss

Radio
Average Ground
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Full Size Dipole H 7 metres Gain
5.1 dBi _at_30 degBW 1 MHz Very GoodNot an SOTA
Antenna.....Great for Field Day

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Case Study 230,17 Metre Trapped Inverted V
18 MHz Trap
Ferrite Choke 6 Sections
T 50-6 Powdered Iron Toroid 22 Turns 30 pF
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Polar Pattern..Elevation Gain _at_ 10 MHz 1.8
dBi17 and 30 metres, Height 7 metres
Broadside 90deg
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Gain _at_ 18 MHz 4.3 dBi17 and 30 metres, Height
7 metres
Broadside 90deg
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Trapped Inverted V 4nec2 SimulationFrequency
Response

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Measured Frequency ResponseAIM 4170 Vector
Meter Tuned Slightly Low (Both Bands)
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Case Study 3 SOTA Antenna Inverted L with one
Insulated Radial20 and 40 metres with tuner
Top
Light weight Height 10 metres Top 8.6
metres Lradial 3.0 metres Radial Height 0.5
metres Wire gage 16 Copper 41 Balun Light
mast guy ropes
Height

Radial
41 Balun
Radio
Feed Point
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Inverted L One Short RadialOptimized for 20
and 40 metresGain (14 MHz) at 30 deg 4.0
dBi.Good
Broadside Radiation

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Inverted L One Short RadialOptimized for 20 and
40 metresGain (7 MHz) at 30 deg -1.0 dBi.OK
End Fire Radiation

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Inverted L One Short Radial Frequency
Response Good SWRZ0 200 ?

Broadside Radiation
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Case 4Buddipole/Hamstick Like Antenna
Small Dipole with Loading CoilGood Field Day
Back Up on 20 metresPoor Choice for 40 or 80
metres

Length 4.9 m Height 3.5 m Lcoil 10 uH Q
100 Average ground
http//www.bing.com/images/search?qsotaantennap
icturesqpvtsotaantennapicturesqpvtsotaanten
napicturesFORMIQFRML
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14 MHz Buddipole/Hamstick Type Dipole
on a Tripod Two Loading CoilsBandwidth 0.2
MHz Gain -1.0 dBi _at_ 30 Deg

Broad Side Radiation
Azimuth 0 deg
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Buddipole Type Dipole on a Tripod Two
Loading Coils Bandwidth 0.2 MHz Might Need A
Tuner14 MHz

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Case Study 5Vertical
DiamondOptimized for 50 ? Input Impedance

Apex Angle
14 MHz L 4.6 m Lcoil 3 uH Base Height 1.0
m Apex Angle 56 deg Total Height 8.1 m (Use a
slightly bigger coil)

Loading Coil Or Trap
Increasing Lcoil
Reduces L and Lowers Gain Still Matched
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Vertical DiamondFour Loading
CoilsGain 3.4 dBi

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Case Study 6Pedestrian Vertical
with Loading CoilOne Trailing Radial (long or
short)
Height 2.0 Metres Radial Height 0.05
Metres Coil Q 100 Copper Wires

East
Walking or Cycling West Radiating East
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Pedestrian Vertical Long Radial BW
0.4 MHzLcoil 14 uH Lradial 4 metres
Gain -6.6 dBi

High Directivity but low gain
Long Radial
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Pedestrian Vertical with Loading CoilOne
Trailing Radial Length 1 MetreGain -11
dBiBW 0.2 MHz
Lcoil 20 uH

Short or no Radial
Bicycle frame acts as a counterpoise
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Case Study 7Short Vertical, Loading
Coil, Four Radials Close to Ground

Height 3.0 Metres Radial Length 1.05
Metres Radial Height 0.05 Metres Lcoil 10 uH,
Q 100

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Gain -7.8 dBi _at_ 30 deg
ElevationZin close to 50 Ohms due to lossesDoes
not meet minimum Gain of -3dBi best to use
PSK31

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Case Study 8End Fed One Wavelength 14 MHz 7
Metres High
Length 18.7 Metres Height 7 Metres at Far
End Feed Point 1 Metre High Feed Point Impedance
1900 ? Counter Poise 1.5 Metres Long
Far End

Feed Point
Max Current High Off Gnd
Transformer 190050 ?
Radio
Counter Poise
Average Ground
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End Fed One Wavelength
Transformer Matched14 MHz Gain 2.6 dBi _at_ 38
deg Azimuth

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Recommended Antennas

• Full Sized Dipole, Inverted V, Diamond
• End Fed, Trapped Inverted V
• Low, small Dipole with loading coils
• Pedestrian (walking or bicycle)very low gain
• Small Vertical with four radialsuse a small
  dipole

73 Dave VE3KL
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Summary

• See my 4nec2 files on ve3kl.com for all details
• Maxwell Ohm give insight
• Simulators crunch numbers
• Only eight case studies given.many more
• Really short antennas are inefficient
• All reasonable portable antennas are fun to use

73 Dave VE3KL