PROPLAB-PRO is the most powerful and accurate ray-tracing radio communication programs in the world and is the only software in the world for personal computers that will accurately ray-trace signals through a realistic three-dimensional ionosphere in three dimensions.

Ray-tracing is the process of modeling the behavior of signals as they travel through the ionosphere. It is the only accurate method for precisely determining how to get a signal from a transmitter to a receiver (or visa-versa), when doing scientific modeling of real-world signal propagation analysis. PROPLAB-PRO comes equipped with one of the most powerful ray-tracing engines in the world, capable of handling such things as:

• Ionospheric Tilts
• Chordal Hops
• Non-Great-Circle Propagation
• Spitzes
• Effects of the Earth's Magnetic Field
• Ordinary and Extraordinary Rays
• Electron collisions (very important)
• Signal Ducting (Inter-Layer Reflections)
• Gray-Line Enhancements
• Signal Strength of Ordinary or Extraordinary Rays
• and MUCH more...

	Click to SECURELY order Proplab-Pro Version 3.0 for delivery via the Internet. NOTE: the downloaded file for Proplab Version 3 measures 260 megabytes in size. Price: $220.00 (USD)
	Click to SECURELY order Proplab-Pro On-Line on CD-ROM for delivery via postal mail. Price: $250.00 (USD)

A sample two-dimensional ray-tracing screen is given below (click on the image for the full screen image) that shows how signals may have traveled between southern Mexico and western South America at 00:00 UTC on 26 October 1995 using a frequency of 10.0 MHz.

In this example, the transmitter is at the far-left corner and the receiver is indicated by the green arrow and the dotted green line. Distances are given in kilometers. The vertical scale defines the altitude above the surface of the Earth in km.

The signal shown was obtained by aiming the antenna at a zero-degree takeoff angle (the signal traveled directly toward the horizon). This produces the longest single-hop paths. The smaller graph at the top shows how the electron density varied as the signal traveled through the ionosphere. The rectangular graph to the right of the electron density graph shows the signal strength in units of dB above 1 microvolt.

The above example was produced using PROPLAB-PRO's simple ray-tracing engine. This engine does not include effects of the Earth's magnetic field or electron collisions and only considers the two-dimensional characteristics of the ionosphere.

For the ultimate in accuracy, PROPLAB-PRO's complex ray-tracing engine should be used, which provides three-dimensional results that includes the effects of the Earth's magnetic field, electron collisions, and the three-dimensional characteristics of the ionosphere.

The following sample shows the ray-traced results over exactly the same path as the simple ray-traced example given above. Notice how much more complex the signal paths really are when compared to the example above obtained using the simpler ray-tracing engine. Since the Earth's magnetic field is included, the principle signal is split into two components. The rays traced in white represent the ordinary signal component. The rays traced in yellow represent the extraordinary signal component.

In this figure, you are looking at the inside of an open box. The transmitter is located in southern Mexico at the position of the green dot on the left-side of the grid. The receiver in western South America is located about 4,000 kilometers distant at the position of the other green dot to the right of the transmitter. The plane on which the transmitter and receiver lie is the surface of the Earth. The straight line connecting the transmitter and receiver represents the great-circle path between these two points. The lines drawn along this plane that are parallel to the great-circle line represent distances away from the great-circle path.

As each ray is traced, a "mirror" of the ray is plotted against the altitude "wall" located along the left-side of the base grid. Another mirror of each traced ray is plotted on the right-side wall which shows whether the ray is deviating from the great-circle path (and if so, by how much and at what altitude). A third mirror of the ray is plotted on the ground (the base grid) showing the ground path of the ray (light-gray in color). And finally, the ray itself is plotted in three-dimensional space beginning at the transmitter. These plots show you everything you need to know to visualize exactly how the rays are behaving in the three-dimensional ionosphere.

The ordinary ray makes a long single chordal hop to a distance of almost 7,000 kilometers and experiences non-great-circle propagation, deviating from the great-circle path by a distance of about 57 kilometers). Radio signals that pass through the equatorial regions (as this example shows) often experience these very-long-distance chordal hops. Ray-tracing is the only accurate method of computing the behavior of signals that undergo chordal hop and non-great-circle propagation.

The extraordinary ray behaves even more radically. This signal experiences numerous chordal hops. It travels a full 12,000 kilometers (the full length of the 3D-grid) and still has not yet reached the ground. The fate of this signal would need to be determined by extending the grid beyond 12,000 km (to say 20,000 km). It may ultimately penetrate the ionosphere, or it may make it to a receiver on the ground somewhere along the way. Signals such as this one often take on a "whispery" tone (similar to ducted signals).

Notice how the rays originally follow the great-circle path until they are about 1,500 kilometers away from the transmitter. At that point, both the ordinary and extraordinary rays begin to deviate away from the great-circle path. In this case, this is due primarily to a tilted ionosphere. Effects of the Earth's magnetic field also contribute to the non-great-circle deviations.

The splitting of the main transmitted signal into ordinary and extraordinary components is extremely important in radio communications because the energy from the main signal is divided into the ordinary and extraordinary components. If the ordinary and extraordinary components diverge (spread apart) as they do in this example, the energy reaching the ground at distant points will be less than if the two component signals stay close together. It is clear that the ordinary and extraordinary rays travel very different paths in this example. By increasing the frequency or varying the elevation angle of the transmission, the deviation of the rays can be decreased which may contribute to overall signal strength.

The reason why the signals deviate from the expected great-circle path is (as was stated above) because of a tilted ionosphere. A cross-section of the ionosphere along the great-circle path is shown here and corresponds to the ray-traced examples above.

This highly useful map was produced by PROPLAB-PRO and shows you how the ionosphere appears cross-wise, as if you were looking at a slab of the ionosphere showing the internal structure of the ionospheric layers. The transmitter in this figure is at the lower-left and the receiver in this example is 12,000 kilometers away at the lower-right. It shows you how the equatorial region of the ionosphere is shaped. Notice how it bulges upward. If the ionosphere were not tilted, the lines in this figure would be perfectly horizontal and flat. This is obviously not the case in this example, which shows many regions where the ionosphere is tilted. Signals that travel through these tilted regions will experience non-great-circle propagation because the tilted layers result in tilted reflections. Using these maps, it is possible to select paths that are stable (or tilted) in order to provide stable or exotic forms of propagation as shown in the 3-dimensional ray-tracing example.

PROPLAB-PRO will display a myriad of global ionospheric maps. This first map is a map showing how geomagnetic latitude maps onto geographic coordinates. Using this map, you can determine what your geomagnetic latitude is. Notice how the magnetic equator deviates strongly from the geographic equator. Geomagnetic coordinates are much more important than geographic coordinates in radio propagation.

Another interesting example is the map given below. This is a map showing the altitude where the electron density reaches a maximum (known as an hmF2 map, or the height maximum of the F2 layer). The contours are labeled in km above the surface of the Earth. Higher F2-layer maximums can result in propagation to much greater distances than the single-hop limit of about 4,000 km. This information is superimposed on an oblique azimuthal equidistant map projection (described below).

This type of map projection is extremely useful for instantly determining the great-circle bearings to distant regions of the world. It is valid for locations near geographic 40N 100W. The great-circle bearing from 40N 100W to any other location in the world can be determined simply by following one of the azimuthal "spokes" to the destination. For example, the great-circle azimuth to the southern tip of South Africa lies at an azimuth of about 103 degrees (measured from the north). The azimuth to Australia is much less sensitive. Transmissions using azimuths between about 250 and 290 degrees will reach Australia provided the signal does not deviate from the great-circle path. In reality, some deviation is almost certain. The extent of the deviation can only be determined through three-dimensional ray-tracing.

The type of antenna that is used to transmit to distant parts of the world is extremely important. PROPLAB-PRO lets you select from numerous pre-made antenna types ranging from sloping wire antennas to multiband aperiodic reflector arrays, etc. You can also create your own if you know the radiation pattern of your antenna.

PROPLAB-PRO will also display selected antenna radiation patterns. This screen shows a pattern for a Sloping-V antenna. The maximum gain of this antenna over an isotropic radiator is 6.2 dBi.

The radiation pattern of an antenna is split into two parts: an elevation angle pattern and an azimuthal pattern. Each of these patterns are displayed above for the Sloping-V antenna. These patterns let you more wisely choose appropriate elevation angles and azimuths to distant reception points. PROPLAB-PRO uses this information to compute signal strengths of traced rays.

Most propagation programs produce graphs showing the MUF (Maximum Usable Frequency) over a period of 24 hours. They accomplish this using empirical algorithms that are created from smoothed statistical results. However, the ionosphere often does not behave in a "smooth statistical" fashion. PROPLAB-PRO tackles this problem by rigorously computing the maximum usable frequency using much more accurate ray-tracing algorithms. Using ray-tracing techniques, much of the guess work is removed.

The maximum usable frequency for any time through a 24-hour period can be determined by examining the green line. The frequency required to reach the receiver must exceed the frequency indicated by the red line or the signal will be reflected by the E-layer and will be more heavily absorbed. The optimum working frequency (or FOT) is indicated by the yellow line and is defined as the frequency corresponding to 85% of the MUF. Frequencies between the magenta colored line and the yellow line are often the best frequencies (most reliable) to use for the given transmitter and receiver. PROPLAB-PRO also considers levels of geomagnetic activity in computing these graphs.

PROPLAB-PRO Version 3.0 is a powerful tool for amateur and professional radio communicators. It is the only software in the world for personal computers that will accurately simulate how signals travel through the ionosphere. It truly is an ionospheric laboratory for your personal computer.

	Click to SECURELY order Proplab-Pro Version 3.0 for delivery via the Internet. NOTE: the downloaded file for Proplab Version 3 measures 260 megabytes in size. Price: $220.00 (USD)
	Click to SECURELY order Proplab-Pro On-Line on CD-ROM for delivery via postal mail. Price: $250.00 (USD)

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