Compact DualMode Mobile HF Antenna System

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Compact Dual-Mode Mobile HF Antenna System

• Michael W. Jacobs
• Star-H Corporation

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Existing Army HF Antennas

• Army field units are increasingly using HF for
  BLOS communications.
• NVIS and long-range modes are used
• Army communications units utilize several antenna
  systems for HF
• 32 Whip Antenna (stationary)
• 16 Whip Antenna (on the move)
• Fanlight Dipole Antenna (long-term stationary)

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New Antenna Requirements

• On-the-move, zero setup time antenna that can
  operate in either NVIS or low-angle mode.
• Low-profile, low-visibility antenna which will
  clear overhead obstructions, trees, power lines,
  etc.
• Rugged antenna that will be reliable in the field.

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Antenna Safety

• CECOM safety guidelines recommend the use of
  low-profile antennas for OTM operations.

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Project Background

• CECOM SBIR topic Low-Profile NVIS HF Antenna for
  TOC/HMMWV
• Star-H personnel previously designed a
  quadrature-fed loop antenna for circular
  polarization for HF heating facility at Arecibo.
• Modify loop to feed symmetrically and fit to
  vehicle form factor.

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Vertical Whip
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Bent Whip
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Vertical Loop
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Dual Vertical Loops
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Horizontal Loop
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Rectangular Loop
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HMMWV/TOC
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2 MHz ComparisonBlue Loop Red
Bent Whip
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7 MHz ComparisonBlue Loop Red
Bent Whip
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12 MHz ComparisonBlue Loop Red
Bent Whip
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Low-Angle Mode
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Input Impedanceat radio connector, NVIS mode
Measured Real top, Imag bottom
NEC Predicted Real red, Imag blue
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Matching Losses
Results for 35 Bent Whip on HMMWV over Average
Ground With 3 meters of 9913 type coaxial cable  
Low-pass L network, QC 1000, QL 200
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Matching Losses
Results for 3 Diameter Loop no HMMWV over
Average Ground Using 2 meters of 7/8 Heliax to T,
3 meters of ½ Heliax to Radio No loading or
optimization of antenna  
Low-pass L network, QC 1000, QL 200
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System Gain ComparisonNo system optimization on
dual loop antenna
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Full-Scale Testing
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Full-Scale Testing Results

• NVIS and Low-Angle pattern switching was
  verified.
• Conducted successful NVIS communications over
  mountainous terrain using both amateur and
  AN/VRC-100 transceivers with ATUs.
• Conducted successful long-range communications
  between Central PA and Virginia Beach,VA.

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Full-Scale Testing Conclusions

• ATUs can match to the antenna, but transmission
  line losses are too high.
• Need to do additional work to improve antenna
  impedance (larger diameter radiator, multiple
  turns, distributed loading).
• Move first stage of matching to antenna
  feedpoints to reduce losses. Initial work shows
  10 dB improvement at 2 MHz.
• Look at revolutionary concepts active antenna
  for receive and transmit?

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Contributors

• Christopher Wantuck, CECOM Tactical Radio
• Dr. James K. Breakall, Penn State University
• Milton D. Machalek, STAR-H Corporation
• Jon Arent, STAR-H Corporation