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Session Overview
W_We_A_Room5: Challenges in Special Applications of Electrically Small, HF Vehicular Antennas (I)
Wednesday, 04/Sep/2019:
9:00am - 10:40am

Session Chair: Diethard E.A. Hansen
Session Chair: Ilona Danelyan
Location: Room 5

Session Abstract

Vehicular, mobile HF (short wave 1.5/3 to 30 MHz, 200/100 to 10m) communication is up today still in beneficial use. Due to ionospheric propagation conditions, under presently low sunspot activities, only the lower spectrum part can mostly be used. Exactly this is a technical challenge, because here electrically short, vertical HF mobile antennas are, from antenna theory basically known, to be inefficient. There is however very little practical, experimental or simulation data available in the open literature. Aside from the military, emergency disaster relief organizations (humanitarian, medical, technical aid) depend on HF mobile on the go. In troubled areas communication infrastructure is mostly gone. Improvised, quick, reliable and still cost-effective deployment is vital. Sat-Com or 3 or 4G mobile phones are often no option. Our detailed experimental and EM-simulation investigations include Automotive EMC, analysis of electrically short HF Antennas, critical communications S/N-ratio, antenna performance impacting parameter studies, rubber tire impact, antenna input impedance, radiation pattern, the impact of soil/ground under the automobile, far-field simulations with absolute antenna efficiency, incl. vertical elevation angle. Validation measurements (groundwave, sky-wave) were performed in the critical low bands of shortwave spectrum around 1.8/3.5/7MHz and above. These representative bands were used base on existing government Amateur Radio transmitting licenses. Antenna efficiency tests by ground-wave propagation were conducted over 2.8 km flat farmland. Sky-wave antenna efficiency test lead to estimates, via statistics, from extended, real world, EU Ionospheric Propagation experiments. The only successful way to address antenna elevation patterns, without having H-field sensing drones available, was to use validated, professional EM-Simulation Codes. Agreement between tests and simulation results are very reasonable, given the many impacting parameters. Innovative antenna design concepts will be discussed.


The general content structure of the workshop is:

  • Motivation, background, open literature, state of the art, interested users
  • Basic technical challenges: Emergency Communication needs in remote disaster areas, Automotive EMC, electrically short HF Antennas, critical communications SNR on short wave low bands
  • Test cars: Mainly Audi A6 Avant, similar in most results to the BMW 316i Touring
  • R&D Antenna design and choice of tested frequency bands were based on an existing government transmission license as HAM radio operator. This allowed in principle use of HF spectrum bands from 1.8 to 29.7 MHz.
  • Antenna problem analysis by equivalent circuit/simulation model (car chassis, tires, short monopole, soil/ground)
  • Efficiency impacting parameter studies (measured/simulated): Tire capacitance impact, Antenna Input Impedance, VSWR (S11), e.g. on 80m (ca. 3.5MHz, R&D Test Antenna, capacitive head, 1.88m long, vertical radiator, large XL resonance coil)
  • Far Field Ant. Radiation Pattern (azimuth, elevation) impact for different soil/ground characteristic under the automobile, incl. simulated ant. efficiency
  • Ant. efficiency-tests by a ground wave over 2.8 km flat farmland, efficiency estimates by statistics from extended EU Ionospheric Propagation experiments. Experimental dB (or %) efficiency => ranking of el. short HF mobile antennas for both R&D, as well as commercial, tested types.
  • Skywave test: Comparing HF mobile to a fixed reference dipole type antenna with a simulated radiation pattern
  • What makes a better radiator? Experiment / Simulation Comparison of two 80m R&D 

  • Antennas over PEC ground (efficiency, elevation angle)
  • Discussion of assumptions/limits in the experiments and how well they fit simulations
  • Outlook: Now we mainly understand the underlying physics. Discussion of ideas to possibly improve antenna principles by innovative procedures and design



Dr. Diethard Hansen

President and Principal Consultant



Ilona Danelyan

EMCoS Ltd. HQ, Georgia

External Resource:
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9:00am - 9:20am

Challenges in Special Applications of Electrically Small, HF Vehicular Antennas

Diethard Hansen1, Ilona Danelyan2


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