ATDI, Inc. recently completed a HF (high frequency) analysis for the United States Coast Guard (USCG), analyzing the coverage capabilities of the existing US Customs and Border Patrol's (CBP) Customs Over The Horizon Enforcement Network (COTHEN) along with existing USCG HF sites nominated for potential inclusion in the existing COTHEN system. Using the most recent version of ITU propagation model 533 (Fig. 1), method for the prediction of the performance of HF circuits, the ATDI team was able to effectively model both existing and potential sites in the COTHEN network for coverage of expansive areas both on- and off-shore.
Figure 1: Example of Point-to-Point skywave propagation chart using ITU-R P.533 HF model
Through the use of point-to-point and point-to-area skywave coverage functions, the ATDI team was able to recommend an updated COTHEN layout designed to expand network coverage along with the bolstering of existing coverage reliability. The analysis considered the many complex characteristics of HF radio propagation including, but not limited to: seasonal variations, daytime/nighttime variations, sunspot numbers, receiver noise environments, required signal-to-noise values, distinctive antenna patterns with prominent vertical nulls, etc.
Figure 2: Predicted HF skywave coverage for hypothetical network (signal-to-noise ratio view)
ATDI, Inc. also recently implemented a bevy of new high frequency (HF) functions into the Spectrum-E web application for the modeling of HF radio propagation. The added functions allow for both point-to-point and point-to-area analysis and the production of visual chart- and map-based result outputs. The ability to model multiple frequencies for one object or a network allows for simplified analysis of ALE (automatic link establishment) networks that frequency-hop through a frequency set, communicating on the most advantageous frequency at any one time. Map-based outputs also allow the user to fine-tune their results for presentation, allowing for both signal-to-noise based plots (Fig. 2) along with percentage of time of day plots (Fig. 3).
Figure 3: Predicted HF skywave coverage for hypothetical network (percentage of time of day view)
Figure 4: Vertical and horizontal polar plots of HF Antenna in Spectrum-E HF module