O. G. Villard

Radio Doppler Investigation of Meteoric Heights and Velocities

A continuous‐wave Doppler method of determining meteoric velocities and heights was tested during the 1948 Perseid meteor shower. The accuracy of the technique was found to compare very favorably with optical and other radio methods. Doppler measurements have the advantage of relatively great sensitivity.

The Role of Meteors in Extended-Range VHF Propagation

It is possible to transmit a continuous signal from point to point by taking advantage of specular reflections from ionization trails formed in the E-region of the ionosphere by meteors of all sizes. A continuous signal is provided whenever such reflections are present in sufficient numbers so that they overlap in time. The factors controlling the degree of overlap are: (1) radio frequency, (2)power (overall circuit sensitivity), and (3) length of path. For best overlap, the individual meteor reflections should be as strong as possible, as numerous as possible, and as long-enduring as possible. If all other parameters are kept the same, lowering the radio frequency increases individual echo strength and duration; raising the power and circuit sensitivity increases not only echo strength and echo duration, but also number of echoes detectable above the noise; and finally, increasing the path length also increases individual-echo duration.

New evidence of anomalous transequatorial ionospheric propagation

Echoes of exceptionally long delay detected by a H. F. radar located in the West Indies are interpreted as ground backscatter propagated by two successive reflections from the F-region of the ionosphere, without intermediate ground reflection. Propagation of this sort between two points on the earth requires an initial ionospheric tilt followed by one of opposite sign. Tilts of the required sort take place regularly in equatorial regions as a consequence of two daily bulges in the ionosphere, one occurring at approximately 1900 local time over the geomagnetic equator, and the other occurring around noon in the vicinity of the sub-solar point. It is shown that tilt-supported propagation can take place at frequencies considerably in excess of the MUF predicted in the usual way. It is believed that these results may explain the reports by radio amateurs of anomalous propagation between North and South America.

Extended-range radio transmission by oblique reflection from meteoric ionization

It has been found that radio communication between relatively low-power stations operating at 14 megacycles and separated by distances of roughly 1200 km may be maintained at times when no layer transmission to any point on the earths surface can be demonstrated to be present. The signal obtained is subject to considerable fading, but some signal is nearly always detectable. The contribution of overlapping oblique-incidence meteor reflections to the observed signal is considered in the light of some preliminary theoretical and experimental findings. It is clearly important to assess the meteoric contribution with care, since the possibility that meteoric reflections alone could account for the signal does not seem unreasonable.