Mode angles of arrival in the 55‐ to 3500‐km range

Abstract

A direction‐finding ionosonde consisting of an interferometer using seven‐element, 50‐ and 150‐meter crossed baselines, has been developed to provide group path delay, azimuth, and elevation of each resolved mode over the sounding frequency range. Direction‐finding (DF) ionograms have been acquired automatically, using various noncooperative, compatible sounder transmissions. Diurnal sequences of DF ionograms were obtained for mid‐latitude paths at nominal ranges of 55‐, 1000‐, 2300‐ and 3500‐km. Data measured to characterize the DF properties of each path include group delay, azimuth, and elevation versus frequency, as well as an azimuth/elevation scatter plot showing the distribution of angular occupancy for the path. The results show modes arriving closest to the great circle bearing (i.e., with lowest azimuth error) arrive via the lowest elevation angles and with least group delay. Fractional degree bearing standard deviations were commonly observed for one‐hop E and one‐hop F low‐ray modes, decreasing with increasing range. Variable bearing standard deviations between 1° and 6° were observed for one‐hop F high‐ray and two‐hop F modes. Bearing standard deviation of 50° were seen at near vertical incidence (55‐km range).

Radio communication via Near Vertical Incidence Skywave propagation: an overview

“…Important parameters for NVIS antenna optimization are antenna diagram, polarization and bandwidth. As only high elevation angles contribute to NVIS propagation [55], optimizing the antenna diagram for these elevation angles will increase the effectively transmitted power and improve the signalto-interference ratio at reception.…”

Application of ionospheric tomography to single‐site location range estimation

“…The raw data collected from the SSL included the azimuth and elevation angles, as well as the signal strength for the signal recorded in each frame. In addition, a phase linear error that describes the deviation from plane wave conditions of the phase resolution across the array was recorded for each frame [7]. Typical distributions in azimuth and elevation are shown in Figure 2…”

Azimuth spread of two‐hop ionospheric modes

“…In this paper, we analyze direction finding (DF) sounding measurements originally reported by Black et al [1995] on one-and two-hop modes, comparing one-hop angular spread resulting from a single traverse of the ionosphere with two-hop angular spread including two ionospheric traverses plus a ground scatter at the path midpoint. We use this data to separate the ionospheric from the ground scatter components of azimuth spread and estimate the ground scatter component separately for two types of terrain.…”