BACKGROUND Travel from countries where viral haemorrhagic fevers (VHF) are endemic has increased significantly over the past decades. In several reported VHF events on airplanes, passenger trace back was initiated but the scale of the trace back differed considerably. The absence of guidance documents to help the decision on necessity and scale of the trace back contributed to this variation.Th...

This paper introduces an interferometric technique for the phase measurement of microwave devices. A handheld vector network analyzer (VNA) is presented for HF and VHF applications. A wideband synthesizer with multiple synchronized outputs is developed for extending the frequency range to the microwave band. The phase differences between the output signals can be set digitally with sub-degree a...

This paper is concerned with the performance of binary frequency-shift keyed (BFSK) communication over frequency-selective fading channels in the tactical VHF range. Channel parameters were extracted from time-series measurements of channel impulse response data. These data were recorded during channel measurements in several mountainous areas in the Austrian Alps with a wideband channel sounde...

The scattering of sound from the sea surface is important for the operation of underwater sonar and underwater acoustic communications systems. Studies of low to mid-frequency surface reverberation have a long history, but studies of very high frequency (>300 kHz) surface scattering in the literature are rare. The physics of very high frequency (VHF) scattering is expected to be strongly depend...

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...