Temporal correlation between atmospheric anomalies and earthquakes has recently been verified statistically through measuring VHF FM radio waves transmitted beyond the line-of-sight. In order to locate the sources of such atmospheric anomalies, we developed a VHF interferometer system (bistatic-radar type) capable of finding the arrival direction of FM radio waves scattered possibly by earthqua...

Distortions are often seen in the angular distribution of echo-power from VHF wind-profiling radars, suggesting that thin stable layers, within the air flow, are distorted and tilted from horizontal. In vertical shear of the horizontal wind, the distribution of the layer tilt angles becomes skewed. A case study using six days of VHF radar data and synoptic charts above western Europe indicates ...

In 2000, we investigated the Rift Valley fever (RVF) outbreak on the Arabian Peninsula-the first outside Africa-and the risk of nosocomial transmission. In a cross-sectional design, during the peak of the epidemic at its epicenter, we found four (0.6%) of 703 healthcare workers (HCWs) IgM seropositive but all with only community-associated exposures. Standard precautions are sufficient for HCWs...

This paper introduces a new dc–dc converter suitable for operation at very high frequencies (VHF) under on–off control. The converter power stage is based on a resonant inverter (the Φ2 inverter) providing low switch voltage stress and fast settling time compared to other resonant topologies. A new multistage resonant gate driver suited for driving large, high-voltage RF MOSFET at VHF frequenci...

The method of moments (MoM) is used to rigorously analyze wide-band VHF scattering from a perfectly conducting trihedral placed above a lossy, dispersive half space. The method of complex images is employed to evaluate the layered-medium Green’s function efficiently and is applied here to the halfspace problem. Particular attention is placed on the physics that underlie scattering from such tar...

A wide variety of unique systems and components inhabits the HF, VHF, and UHF bands. Many communication systems (ionospheric, meteor-burst, and troposcatter) provide beyond-line-of-sight coverage and operate independently of external infrastructure. Broadcasting and over-the-horizon radar also operate in these bands. Magnetic-resonance imaging uses HF/VHF signals to see the interior of a human ...

In this paper, an ultra-low-noise amplifier with frequency band switching capability is designed, simulated and fabricated. The two frequency ranges of this amplifier consist of the 2.4 to 2.5 GHz and 3.1 GHz to 3.15 GHz frequency bands. The designed amplifier has a noise figure of less than 1dB, a minimum gain of 23 dB and a VSWR of less than 2 in the whole frequency band. The design process s...

Vessel Traffic Service (VTS) significantly improves the navigation efficiency of ports. This paper proposes a model called Joint Extraction Triples from VHF Speech (JER-VHF) to ensure VTS. Numerous texts are extracted Very High Frequency (VHF) speech communication contents and these organized into dataset named VHFDT. The proposed model's transforming task transforms voice this triple represent...

Lightning dart leaders and recoil are current pulses that propagate along previously established lightning channels reionizing the channel. They poorly understood since it is not known how a ionized channel can undergo dielectric breakdown multiple times. In this work we investigate five on two different using observations of LOFAR radio telescope in vhf (where observe 30--80 MHz) our TRI-D int...

Recently, a new lightning phenomena, termed needles, has been observed in both VHF and optical along positive leaders. They appear as small (<100 m) leader branches that undergo dielectric breakdown at regular intervals (called twinkles). Providing coherent consistent explanation for this phenomenon is challenging each twinkle form of negative propagates away from the leader. In study, we provi...