Compact Dual-Mode Mobile HFCompact Dual-Mode Mobile HF Antenna System

Michael W. JacobsStar-H Corporation

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 y

antenna systems for HF:– 32’ Whip Antenna (stationary)– 16’ Whip Antenna (on the move)– Fanlight Dipole Antenna (long-term stationary)

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.

Antenna Safety

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

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.

Vertical Whip

Bent Whip

Vertical Loop

Dual VerticalDual Vertical Loops

HorizontalHorizontal Loop

RectangularRectangular Loop

HMMWV/TOCHMMWV/TOC

2 MH C i2 MHz ComparisonBlue = Loop Red = Bent Whip

7 MH C i7 MHz ComparisonBlue = Loop Red = Bent Whip

12 MH C i12 MHz ComparisonBlue = Loop Red = Bent Whip

Low-Angle Mode

Inp t ImpedanceInput Impedanceat radio connector, NVIS mode Measured

Real = top Imag = bottom

2 00E+01

2.50E+01

3.00E+01

3.50E+01NEC PredictedReal = red, Imag = blue

Real top, Imag bottom

0 00E+00

5.00E+00

1.00E+01

1.50E+01

2.00E+01

Series1

0.00E+00

2000

000

3679

664

5359

328

7038

992

8718

656

1039

8320

1207

7984

1375

7648

1543

7312

1711

6976

1879

6640

2047

6304

2215

5968

2383

5632

2551

5296

2719

4960

2887

4624

1 50E+02

2.00E+02

2.50E+02

-5.00E+01

0.00E+00

5.00E+01

1.00E+02

1.50E+02

2000

000

3819

636

5639

272

7458

908

9278

544

1109

8180

1291

7816

1473

7452

1655

7088

1837

6724

2019

6360

2201

5996

2383

5632

2565

5268

2747

4904

2929

4540

Series1

-2.50E+02

-2.00E+02

-1.50E+02

-1.00E+022 3 5 7 9 11 12 14 16 18 20 22 23 25 27 29

Matching LossesResults for 35’ Bent Whip on HMMWV over Average Ground

With 3 meters of 9913 type coaxial cableWith 3 meters of 9913 type coaxial cable

Freq. (MHz)

R X Antenna Gain at Zenith

Tuner and Transmission

Line Loss (3 m 9913)

Net Gain at Zenith

Power into

Antenna for 150W

inputinput2 7.05 -1074 -7 dB 11.88 dB -18.88 dB 9.7 W

7 34.4 -67.1 -0.7 dB 0.12 dB -0.82 dB 145.8 W

12 247.3 497.1 2.82 dB 0.45 dB 2.37 dB 135.3 W

17 485.2 -875 5.15 dB 0.92 dB 4.23 dB 121.4 W

22 82.8 -112 5.39 dB 0.21 dB 5.18 dB 142.9 W

29 304.6 488.8 4 dB 0.71 dB 3.29 dB 127.4 W

Low-pass L network, QC = 1000, QL = 200

Matching LossesResults for 3” Diameter Loop no HMMWV over Average GroundUsing 2 meters of 7/8 Heliax to T, 3 meters of ½” Heliax to RadioUsing 2 meters of 7/8 Heliax to T, 3 meters of ½ Heliax to Radio

No loading or optimization of antennaFreq. (MHz)

R X AntennaGain at Zenith

Tuner and Transmission

Line Loss (Heliax)

Net Gain at Zenith

Power into

Antenna for 150W(Heliax) for 150W

input

2 0.817 -3888 -6.6 dB 34.79 dB -41.4 dB 0.05 W

7 2 03 1081 1 86 dB 18 51 dB 16 65 dB 2 1 W7 2.03 -1081 1.86 dB 18.51 dB -16.65 dB 2.1 W

12 5.05 -591.6 4.58 dB 9.46 dB -4.88 dB 16.99 W

17 11.5 -372.4 5.11 dB 4.90 dB 0.21 dB 48.5 W

22 23.59 -238.1 5.68dB 1.83 dB 3.85 dB 98.4 W

29 42 7 142 5 97 dB 0 56 dB 5 41 dB 131 9 W29 42.7 -142 5.97 dB 0.56 dB 5.41 dB 131.9 W

Low-pass L network, QC = 1000, QL = 200

System Gain ComparisonSystem Gain ComparisonNo system optimization on dual loop antenna

Zenith Gain of Bent Whip and Dual Loop

0

10

-20

-10

02 7 12 17 22 29

ain,

dB

i

32' Bent WhipNVIS Dual Loop

-40

-30Net G

a

16' Bent Whip

-50

Frequency, MHz

Full-Scale Testing

4’ 6” long-7/8” dia. Coax jumper

T-Connector

3/4” Copper Tubing

Coax jumper

7’ 7” long -7/8” dia. Coax to Radio Set Inside TOC

Insulated Feed Gap with Ferrite Balun(one each side)

Full-Scale Testing Results

• NVIS and Low-Angle pattern switching was verified.

• Conducted successful NVIS communications over mountainous terrain using both amateur and

/ i i hAN/VRC-100 transceivers with ATU’s.• Conducted successful long-range communications

b t C t l PA d Vi i i B h VAbetween Central PA and Virginia Beach,VA.

Full-Scale Testing Conclusions

• ATU’s can match to the antenna, but transmission line losses are too high.

d d ddi i l k i• Need to do additional work to improve antenna impedance (larger diameter radiator, multiple turns, distributed loading).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 i d t it?receive and transmit?

Contributors

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