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Emerging data processing techniques brought back into attention the HF range communication as an interesting alternative to third-party solutions for IoT applications, such as data transmission in distributed energy production facilities. The physical size of HF antennas, often comparable to the surrounding objects, require in situ radiation measurements resulting in site-customized antenna design and positioning, and consequently in a higher reliability of such HF grid communications. Drone-borne measuring systems are already known as a flexible solution, but are mostly restricted to higher frequency ranges where full-wave, wide-band probes are feasible. In this work, we propose to use an electrically small, folded dipole as a probe for drone-borne measurements on HF antennas. We also propose a calibration approach for the effects related to the near-field zone, and to the drone body proximity; corrections on these two effects are the key methodological steps. We show that despite a realized gain figure in the order of −20 dBi, such a probe can provide stable results for near-field measurements, even at input power levels as low as 1 mW. Compared to other similar approaches, our configuration provides a wider frequency band of operation, higher stability in terms of pattern diagram, and a lower cost. [ABSTRACT FROM AUTHOR]

The design of high‐power vehicle‐mounted log periodic dipole antenna for 8‐22 MHz use was discussed. It is shown that the antenna has a power endurance of 150 kW. With the application of the coefficients variation method, the total size of the proposal was shrunk to 12 × 18 m so that it can be mounted on a vehicle of 10 m long by an elevation tower. The voltage standing wave ratio over the entire frequency band is lower than 2.0 without utilizing any match network. [ABSTRACT FROM AUTHOR]

Design of low-profile vehicular on-the-move (OTM) wideband high-frequency (HF) antennas with 24-kHz instantaneous bandwidth for near-vertical communications is discussed. It is shown that multiarming significantly reduces the minimum antenna height, whereas the two-arm configuration is a tradeoff between antenna complexity and performance. A procedure for determining the minimum antenna height when the tuner loss is considered as a design parameter is introduced. The design evolves from a state-of-the-art magnetic dipole to a wire two-arm half-loop antenna (HLA). The profile for the amphibious assault vehicle (AAV) mounted antenna is 0.65 m ($\lambda/230$ at 2 MHz) for the parabolic shape and 0.50 m ($\lambda/300$) for the rectangular shape two-arm half-loop. The length of antenna base is 4.8 m ($\lambda/31$) and the width is 3.3 m ($\lambda/45$). A simple two-element tuner is considered in the scope of the results validation, along with the impedance and directivity patterns measurements on scaled 1/500 models. [ABSTRACT FROM PUBLISHER]

The bottom side of a vehicle is assessed for mounting HF-VHF antenna systems in terms of omni-directionality, efficiency and propagation loss. Accurate and numerically efficient procedure for calculation of propagation loss associated with sources electrically close to real grounds is proposed and carefully validated. It is shown that even though bottom sources cannot compete with conventionally mounted antennas in terms of far field omni-directionality and efficiency, in the near field region propagation loss margins are comparable for distances shorter than 10 m and frequencies from 20 to 100 MHz. The result points to the frequency range where antennas can be concealed at the bottom side and still used for emerging short distance applications. [ABSTRACT FROM PUBLISHER]

This paper presents a novel antenna architecture to achieve an extremely small form factor for HF band applications. The approach is based on manipulating the topology of a short monopole antenna without utilizing a high index material. A new architecture incorporating two radiating elements is configured, which allows significant gain enhancement. It is shown that such architecture can render a miniaturized HF antenna on air substrate having lateral and height dimensions as small as 0.0115\lambda0 \times 0.0115\lambda0 \times 0.0038\lambda0 (150 mm\,\times\,150 mm\,\times\,50 mm for operation at 22.9 MHz). It is found that the measured gain of such architecture can be as high as -18.1 dBi, which is 16.7 dB higher than a reference inverted-F antenna realized on a high index material (\varepsilonR =10.2) having exactly the same dimensions. The proposed antenna architecture is composed of two in-phase radiating vertical elements connected to two inductors between which a capacitive top load is connected to achieve the desired resonant condition. The two vertical elements act effectively as a monopole having increased height. It is also shown that the gain of the antenna can be increased monotonically by increasing the quality factor (Q) of the phase shifter. High Q air-core inductors that can be accommodated in electrically small monopole antenna are designed and incorporated in the phase shifter to achieve a gain value of -17.9 dBi. Details about the proposed design approach, simulation, and measurement results are discussed. [ABSTRACT FROM PUBLISHER]