Copyright: Copyright © 2001-2002 Sheldon C. Shallon, W6EL
Citation: Copyright © 2001-2002 Sheldon C. Shallon, W6EL


W6ELProp Help Contents
W6ELProp™ Help Contents

W6ELProp

W6ELProp Propagation Predictions

The W6ELProp Maps

The W6ELProp Atlas

Options

Operating Aids

Fundamentals of Ionospheric Propagation

W6ELProp Files

License Agreement


W6ELProp
W6ELProp™

W6ELProp™ is a computer program for predicting ionospheric (sky-wave) propagation between any two locations on the earth on frequencies between 3 and 30 MHz. W6ELProp runs under the Microsoft® Windows® operating system. It is the Windows version of the earlier MINIPROP™ and MINIPROP PLUS™ propagation prediction programs that ran under the MS-DOS® operating system. These programs employ a unique mode-searching algorithm that takes into account the D, E, and F layers of the ionosphere when computing predicted received signal levels. The algorithm searches through the potential ionospheric modes (combination of E and F hops) and finds the mode yielding the strongest received signal. Signal levels and other useful information for this strongest mode are calculated for up to ten HF frequencies of your choice and for every half hour of the day. Maximum usable frequency (MUF) calculations use a superior F-layer method developed at the BBC by Raymond Fricker [1], combined with the E-layer method presented in a report of the International Radio Consultative Committee (CCIR) of the International Telecommunication Union [2]. W6ELProp was programmed in the Delphi™ application development environment.

Users of the later versions of MINIPROP PLUS may notice small differences between the predictions of those programs and W6ELProp; these result from minor refinements in the prediction calculations.

W6ELProp is best viewed with a minimum screen resolution of 800 by 600 pixels and a minimum color setting of 256 colors.

The copyright to W6ELProp is owned by its author, Sheldon C. Shallon, W6EL. No charge may be made for its distribution. License to use W6ELProp for non-commercial purposes is granted to individuals at no charge. Businesses and government agencies should contact the author to make licensing arrangements.

The author would appreciate being notified of any problems you encounter with W6ELProp or this help file, and of any suggestions you may have. Unfortunately, there is no guarantee of a reply or of a problem correction.

1.	Fricker, R., A Microcomputer Program for the Critical Frequency and Height of the F Layer of the Ionosphere, Fourth International Conference on Antennas and Propagation, pp. 546-550, Institution of Electrical Engineers (UK), 1985.

2.	CCIR, CCIR Atlas of ionospheric characteristics, Report 340, International Telecommunication Union, Geneva, 1983.


W6ELProp Main Menu Bar

The W6ELProp Main Menu Bar appears below the title bar in the W6ELProp opening window.

File

Predictions

Maps

Atlas

Options

Operating Aids

Help


W6ELProp Propagation Predictions

The commands in the Predictions menu allow you to run a W6ELProp On-Screen Propagation Prediction and to run W6ELProp Batch Predictions.

On-Screen

Batch


Running an On-Screen W6ELProp Propagation Prediction

Choose Predictions from the W6ELProp Main Menu Bar and then choose On-Screen.

A dialog box will appear. Enter the data asked for in the dialog box. Click the OK button or press the F9 key after you have entered the required information. The Path Information window will display while W6ELProp computes the prediction.

W6ELProp Propagation Prediction Dialog Box

Path Information Window

W6ELProp Prediction Window


W6ELProp Batch Predictions

Choose Predictions from the W6ELProp Main Menu Bar  and then choose Batch.

The major portion of the Batch Predictions window is the Batch Table in which you can enter the input parameters needed to compute up to 15 predictions. Batch Tables can be saved on disk and recalled for possible later editing and reuse.

When entering a parameter into a cell in the table, pressing the Insert key will copy the entry from the cell above into the current cell (except in row 1).

When you press the Print Predictions button, the predictions will be computed in sequence without your interaction between predictions, and each of the predictions will be sent to your printer (or to a file if you select Print to file in the Print dialog box). The letters “OK” will appear to the right of each row in the Batch Table to indicate that the prediction has been computed and printed, but a red letter “X” will appear if one or more of your input parameters is missing or invalid. Printed predictions have the same format as predictions that are displayed in the W6ELProp Prediction Window, and will display signal predictions as signal levels or S/N ratios according to your Primary Signal Display selection in Options.

The predictions will be computed for each of the frequencies specified in Options.

Terminal A or Terminal B Prefix or Locator

Enter DEFAULT or press the F7 function key if you want to use the default terminal.

To use a W6ELProp atlas entry, enter the country prefix (or other unique identifier) of the atlas entry. If you are not sure of the prefix you want, press the F8 function key. You will then be able to scroll through the atlas alphabetically by prefix or name. To move quickly to an area of the atlas, just start typing the prefix or name of an entry; the highlight bar will jump to the first matching entry, or to the next entry if there is no match. When the entry you want is highlighted, click OK or press the Enter key to complete the entry.

If you want to use an IARU Grid (Maidenhead) Locator, enter the four- or six-character Locator of the terminal. The first two characters must be letters, the next two characters must be numeric digits, and the next two characters, if used, must be letters. W6ELProp will compute the latitude and longitude of the center of the “square”, and will use these values when computing the prediction.

Date

See Entering the Date

Solar Index

See Entering the Solar Index

K Index

See Entering the K Index

Path

Enter S for short path, L for long path, or B if you want the prediction to be computed for both paths.

Notes

This column is for your use. It has no effect on the predictions.

File Menu Commands

• New	This command clears the Batch Table.

• Open	Use this command to open a previously saved Batch Table.

• Save	Use this command to save the current Batch Table on disk. When you save a Batch Table for the first time, W6ELProp displays the Save As dialog box so you can type a name and location for the file.

• Save As	This command allows you to save a Batch Table under a new name or in a new location.

• Close	Closes the Batch Prediction window and returns to the W6ELProp Main Menu.

Toolbar

The Toolbar buttons perform the same functions as the New, Open, and Save File Menu commands.


W6ELProp Propagation Prediction Dialog Box

To compute a propagation prediction between two terminals, W6ELProp needs to know the locations of those terminals. W6ELProp refers to the terminals as Terminal A and Terminal B. You will enter the locations of the two terminals, the date, solar index, and K index in the dialog box.

OK (F9)

Click this button or press the F9 key after you have entered the required information. The Path Information window will display while W6ELProp computes the prediction.

Cancel

Cancels the prediction and returns to the W6ELProp opening window.

Entering Terminal Data

Entering the Date

Entering the Solar Index

Entering the K Index

Path Information Window

W6ELProp Prediction Window


Entering Terminal Data

There are four ways you can tell W6ELProp the location of a terminal:

•	If you want to use a W6ELProp atlas entry, enter in the Prefix or Locator field the country prefix (or other unique identifier) of the atlas entry. W6ELProp will search the atlas to find the matching entry, and will use the data in that entry to fill in the Latitude, Longitude, and Name fields. If you are not sure of the prefix you want, click the Select From Atlas button or press the F8 function key. You will then be able to scroll through the atlas alphabetically by prefix or name. To move quickly to an area of the atlas, just start typing the prefix or name of an entry; the highlight bar will jump to the first matching entry, or to the next entry if there is no match. When the entry you want is highlighted, click OK or press the Enter key to complete the entry.

•	If you want to use an IARU Grid (Maidenhead) Locator, enter in the Prefix or Locator field the four- or six-character Locator of the terminal. The first two characters must be letters, the next two characters must be numeric digits, and the next two characters, if used, must be letters. W6ELProp will compute the latitude and longitude of the center of the “square”, and will fill in the Latitude and Longitude fields with these values.

•	To use the default terminal location, click the Use Default button or press the F7 key. (If the Prefix field is empty, pressing the Enter key will have the same effect as pressing F7.) W6ELProp will look in the W6ELProp.SAV disk file for the latitude, longitude, and name of the default terminal, and will fill in the corresponding fields for you. If you have not already created a default terminal for your own location, you may do so by choosing Options from the W6ELProp Main Menu Bar.

•	To manually enter the latitude, longitude, and name from the keyboard, click the Enter Manually button or press the Insert key. For information on entering the latitude and longitude, see About Latitudes and Longitudes. In the Name field, enter a call sign, city name, or other identifier. The name you enter will appear in W6ELProp windows as an identifier for your use. W6ELProp makes no other use of the name.

The W6ELProp Atlas


About Latitudes and Longitudes

In W6ELProp a location is defined by its geographic latitude and longitude.

Latitude is a measure of angular distance north or south of the equator. It is measured in degrees. The latitude of the equator is 0 degrees. The north pole is at 90 degrees north latitude, and the south pole is at 90 degrees south latitude. Latitudes can never exceed 90 degrees in magnitude. To distinguish between north and south latitudes, the latter must be preceded by a minus (–) sign or followed by the letter S. For example, 40 degrees north latitude would be entered as 40; 40 degrees south latitude would be entered as –40 or 40 S. You may place a plus (+) sign in front of north latitudes, but it is not required.

Longitude is a measure of angular distance east or west of the prime (Greenwich) meridian. It is measured in degrees. The longitude of the prime meridian is 0 degrees. Longitudes to the west of the prime meridian (e.g., in the western hemisphere) are west longitudes. Longitudes to the east of the prime meridian (e.g., in the eastern hemisphere) are east longitudes. The meridian half way around the world from the prime meridian is at longitude 180 degrees; its longitude can be given as either 180 degrees west or 180 degrees east. Longitudes usually have magnitudes between 0 and 180 degrees. However, any particular meridian of longitude can be reached by traveling either east or west from the prime meridian. Therefore, a longitude of 90 degrees west is equivalent to a longitude of 270 degrees east, for example. W6ELProp will accept longitudes with magnitudes between 0 and 360 degrees. To distinguish between west and east longitudes, the latter must be preceded by a minus (–) sign or followed by the letter E. For example, 100 degrees west longitude would be entered as 100; 100 degrees east longitude would be entered as –100 or 100 E. You may place a plus (+) sign in front of west longitudes, but it is not required.

An atlas file containing latitudes and longitudes of several locations is supplied with W6ELProp, but you will also have need for your own latitude and longitude, and you may wish to use latitudes and longitudes of other locations that are not in the W6ELProp atlas. You can generally find this information in atlases that are available in bookstores and libraries, or you may scale them from maps or charts. A note of caution is in order regarding latitudes and longitudes that are tabulated in atlases: they may be shown as decimal numbers, but often are in a degree.minute format. Thus, 40.54 might mean 40.54 degrees, but it often means 40 degrees, 54 minutes. If the latter is meant, the equivalent decimal value is 40.9 degrees.

W6ELProp will accept latitudes and longitudes as decimal degrees or in a degree minute second format. If you wish to enter a latitude or longitude in the latter format, leave one blank space between the degrees and minutes, and another between the minutes and seconds, if any. Here are some examples. All the values in each column are equivalent.

40.9	0.5	–28 10 30	–135 (east longitude)
40 54	00 30	–28 10.5	225 (west longitude)
40 54 0	00 30 0	–28.175	+225
40 54 00	00 30 00	135 E
+40 54 00

The following entries are invalid.

“33 60”	(Minutes and seconds must be less than 60.)

“118 25”	(Too many blank spaces.)

“–34 –25”	(Put minus sign in front of degrees only.)

“-40 S”	(Do not mix sign and direction indicator letters.)

“85.5 25”	(Decimal allowed only in last part of entry.)

“91”	(If a latitude, may not exceed 90.)

“361”	(Longitudes may not exceed 360.)

A span of one degree of latitude, or one degree of longitude at the equator, is equivalent to a distance of approximately 111 km (69 mi). This is sufficient accuracy for most predictions. If you enter latitudes and longitudes to the nearest minute, the location accuracy is improved to approximately 2 km (1 mi). You can specify latitudes and longitudes to the nearest second if you know the coordinates to this accuracy, but in only rare circumstances will this result in greater prediction accuracy.


Entering the Date

Dates are entered in MMDDYY, DDMMYY, or YYMMDD sequence according to your date format specification in the Regional Settings of Windows. (MM are the two month digits, DD are the two day digits, and YY are the last two year digits.) YYMMDD is the default sequence in the event that W6ELProp is unable to obtain your date format from Windows. Valid day values are 00 through 31, month values are 01 through 12, and year values are 00 through 99. Note that W6ELProp uses only two digits for the year; the YY digits of your entry will be interpreted as a year between 1945 and 2044, inclusive. This 100-year span allows you to obtain current predictions, to compare W6ELProp predictions with actual propagation records back to the beginning of the post-WW II DXCC, and to predict propagation well into the future.

If you wish, you can skip the date separators (e.g., - or /) and enter only the numerals; W6ELProp will enter the separators for you, using the separator specified in the Regional Settings of Windows.


Entering the Solar Index

You will have to enter a sunspot number or solar flux value when you run a W6ELProp prediction or use the Frequency Map.

Precede the number you are entering with S if it is a sunspot number, or F if it is a solar flux value; e.g., S75 or F132.5. However, you do not have to enter the letter if you have designated that index as your primary solar index in W6ELProp Options.

If you have access to daily values of solar flux, it is recommended that you use these values. Even better agreement between predicted and observed propagation is usually obtained by using the average of the solar flux values for the past 3 to 5 days. The reason for this is that MUFs appear to respond slowly to day-to-day changes of solar input, with an integration time of a few days.

Correlation of daily, or even monthly, values of sunspot numbers and solar flux is poor. A range of sunspot numbers can correspond to a particular value of solar flux, and vice versa. However, 12-month running averages of these two indices are highly correlated with each other. Various formulas to approximate the relationship between sunspot number and solar flux have appeared in the literature. W6ELProp uses the following formula:

12-month running average solar flux = 63.75 + 0.728 ssn + 0.00089 ssn2

In this formula, ssn is the 12-month running average (smoothed) sunspot number. The solar flux is in units of 10-22 watt per square meter per Hz measured at a frequency of approximately 2800 MHz (10.7 cm).

As a result of the annual variation of the distance between the Earth and the sun, a given level of 2800-MHz radiation from the sun results in somewhat different values of solar flux measured at the Earth (and reported on WWV and WWVH) at different times of the year. W6ELProp uses the above formula to convert between solar flux value and sunspot number, and also corrects for the varying Earth-to-sun distance. For this reason, the sunspot numbers and solar flux values displayed by W6ELProp generally will not be related in strict accordance with the above formula.

W6ELProp will accept sunspot numbers between 0 and 360, and solar flux values between 60 and 410. If you enter a solar flux value that would correspond to a negative sunspot number, W6ELProp will substitute the solar flux value corresponding to a sunspot number of 0.

To analyze propagation more than six months in the past, or to forecast future propagation, it is recommended that you use historical or forecast 12-month smoothed monthly sunspot numbers that are available at various Internet Web sites.


Entering the K Index

The K index, on a scale of 0 to 9, is a measure of the variation of the magnetic field of the Earth from quiet conditions. The Boulder K index is usually derived from magnetometer measurements made at the Table Mountain Observatory north of Boulder, Colorado. Every three hours, a new K index is determined and the WWV and WWVH broadcasts are updated.

Enter an integer between 0 and 9. Use –1 (or leave the K index blank) if you want the prediction or Frequency Map calculations to be based on an average K index (approximately 2 or 3).

MUF (maximum usable frequency) predictions in W6ELProp are a function of the K index you enter; thus predicted MUFs and the W6ELProp Frequency Map are directly affected by the K index. Note that MUFs do not always decrease as the K index increases—the inverse relationship sometimes exists—so you will sometimes see higher predicted MUFs with elevated values of the K index. Since mode availabilities and mode-searching signal level predictions are a function of predicted MUFs, you will frequently find that these change when you change the K index. Mode-searching predictions of hop configurations and radiation angles may also change as a function of K index.

Increased signal absorption will occasionally occur at mid-latitudes during periods of elevated K indices, and at high latitudes the absorption will be very severe on most occasions, but prediction of these effects is beyond the capability of W6ELProp. In general, the responses to a given geomagnetic field disturbance are not identical on any two paths, and on a given path the responses may differ as a function of date, time of day, and solar index.


Path Information Window

The Path Information window is displayed while W6ELProp computes the prediction. You may also view the Path Information window by clicking Info on the menu bar of the W6ELProp Prediction window and the Advanced Prediction window.

Below the heading are two columns of information, one for each terminal. For each terminal, the latitude and longitude are shown in decimal format. Although shown to two decimal places, latitudes and longitudes are carried to greater accuracy within W6ELProp.

Sunrise and sunset times and directions of the gray line at these times are shown for each terminal. There are several definitions of sunrise and sunset (e.g., civil, nautical, astronomical), and times can differ by several minutes among the different definitions. W6ELProp defines sunrise and sunset as the times when the center of the sun is on the celestial horizon. The gray line, or terminator, is the dividing line between the sunlit and the dark parts of the Earth. For each sunrise and sunset, the first gray line direction shown is the most northerly direction and the second direction is the most southerly; the two directions are 180 degrees apart. Many DXers point their antennas along the gray line at sunrise and sunset to look for DX.

Next, the bearings are shown for both the short great circle path and the long great circle path between the two terminals. Note that except for some special cases, the bearings from Terminal A to Terminal B, and from Terminal B to Terminal A on the same path, will not be 180 degrees apart, but the short-path and long-path bearings from any one terminal are 180 degrees apart from each other.

The short-path and long-path distances between the two terminals are shown next. Distances are given in kilometers, nautical miles, and U.S. statute miles.

The Polar notation that sometimes appears in parentheses alongside the distances is an advisory that the path passes through a polar area in which polar cap absorption (PCA) events occur. When this advisory appears, you should keep in mind that increased signal absorption may greatly reduce received signal levels during PCA events. When the advisory appears, it will usually do so for both the short and long paths; however, it is possible for the advisory to appear for only one of the paths because the two polar cap areas are not directly opposite each other on the Earth. (Increased absorption will frequently occur in the polar areas during geomagnetic storms also—but the areas affected are less well defined and will occasionally extend to mid-latitudes.)


W6ELProp Prediction Window

The major portion of this window is the primary table of predictions for MUFs and signal levels (or signal-to-noise ratios if you have selected S/N Ratios as your preferred mode for the display of signal predictions; you can select either Signal Levels or S/N Ratios as the preferred mode). These are displayed for every half hour UTC. (One of the options allows you to have all times displayed in your local time.)

MUF

The frequencies in the MUF column are the predicted MUFs for the path. Each of the MUFs is the highest of the MUFs for all the possible ionospheric modes between the two terminals at the indicated time. You probably will not refer to the MUFs too frequently because the predicted signal levels and availabilities give you the information you need to anticipate openings on your chosen frequencies.

Signal Levels

Predicted signal levels are shown for each of your default frequencies. (The Options choice in the Main Menu allows you to change the default frequencies.) W6ELProp searches through the potential ionospheric modes (combination of E and F hops) and finds the mode yielding the strongest signal at each half hour and on each frequency. The signal levels are in dB with respect to 0.5 microvolt in series with 50 ohms, and assume a matched antenna load. Typically, 0.5 microvolt produces an S3 signal. So 0 dB would be S3. At 5 dB per S unit, typical of many amateur receivers, 10 dB would be S5, 30 dB would be S9, etc. The signal levels assume 100 watts radiated power with half-wave dipole antennas in free space at both ends of the path, and with the antennas oriented for maximum gain along the path.

You may specify optional constants, one per frequency, that W6ELProp will include in its signal level calculations to add or subtract whatever number of dB you think appropriate for the antennas and power levels in use on that frequency; choose Options in the Main Menu.

Note that the predicted peak signal level generally decreases as the frequency increases. This results from the assumption of half-wave dipole antennas in free space at both ends of the path, which is equivalent to assuming constant antenna gain at all frequencies. In practice, antennas used on 80 and 40 meters usually have lower gain than those used at higher frequencies.

The display of signal levels below -10 dB (with respect to 0.5 microvolt) is normally suppressed (not shown) because weaker signals are generally unusable. The suppression threshold can be changed if you wish; choose Options in the Main Menu.

Signal-to Noise Ratios

Predicted S/N ratios are shown for each of your default frequencies. (The Options choice in the Main Menu allows you to change the default frequencies.) The noise calculation includes both galactic and man-made noises. You may specify the level of man-made noise according to your station environment (industrial, residential, rural, or remote); choose Options in the Main Menu. W6ELProp assumes that the same noise environment exists at both ends of the path.

When converting signal level to S/N, W6ELProp uses a default noise bandwidth of 1 Hz. However, you may change this default noise bandwidth; choose Options in the Main Menu. If you mostly use only one communication mode, you may prefer to set the default noise bandwidth to the receiver bandwidth you use for this mode (for example, 2400 Hz for SSB or 500 Hz for CW). In this case, the displayed signal-to-noise ratios will be relative to the noise in this bandwidth.

Note that atmospheric noise is not included in the S/N calculation, and may be strong enough to preclude your taking advantage of the predicted signal levels and signal-to-noise ratios. For example, on the lower frequencies—particularly 80 meters—summertime atmospheric noise propagated at night via the ionosphere from a great number of distant overlapping lightning discharges can make even S9 signal levels unusable.

Availability

The letters A, B, C, and D following the predicted signal levels are included to indicate the predicted availability of the strongest ionospheric mode. Availability is the probability that the frequency at the top of the column will be less than the mode MUF; availability can be thought of as the probability that the mode will indeed exist. Note that availability depends on frequency and MUF, but is independent of signal level. The availability letters have the following meanings:

Percent Availability

A	75 to 100

B	50 to 75

C	25 to 50

D	1 to 25

The display of signal levels is normally suppressed (not shown) when the predicted availability is zero. This suppression can be canceled if you wish; choose Options in the Main Menu. If you cancel the suppression, the absence of a letter following a displayed signal level will indicate zero predicted availability.

Toggling Between Signal Levels and Signal-To-Noise Ratios

Noise picked up by the receiving antenna may preclude your taking advantage of the predicted signal levels. In this case, you may find predicted signal-to-noise ratios more useful than predicted signal levels.

If you wish to view the current prediction in terms of S/N, click the Show Signal-to-Noise button. Clicking the button again will restore the signal level display. W6ELProp predictions are always calculated as signal levels, but are converted to signal-to-noise ratios when you choose the S/N display.

Toggling Between Short Path and Long Path Predictions

Click on the Show Long Path button to see the prediction for the long great circle path [1].

Keep in mind that the mechanics of long-path propagation are not completely known, which makes long-path propagation difficult to predict reliably. Predicted openings often do not occur, particularly on the higher frequencies. On the lower frequencies, openings are frequently shorter than predicted, but actual signal levels are often stronger than predicted.

Click on the Show Short Path button to return to the short path predictions.

Close

Closes the Prediction window and returns to the W6ELProp Main Menu.

Prediction Window Menu

The following choices are available in the Prediction window menu.

File

Info

Maps

Graphs

Advanced

1.	Brown, R. R. (NM7M), Long-Path Propagation, published privately, March 1992.


The W6ELProp Maps

The commands in the Maps menu allow you to display the W6ELProp rectangular and great circle maps.

Frequency Map

Rectangular and Great Circle Maps

Print Great Circle Map


W6ELProp Rectangular and Great Circle Maps

These maps are available as choices in the Maps menu on the W6ELProp Main Menu Bar, and in the Maps menu on the menu bar of the W6ELProp Prediction window. When you access one of the maps from the W6ELProp Main Menu Bar, a dialog box will appear so you can specify the terminal locations, date and time; see Rectangular and Great Circle Map Dialog Box. If accessed from the Prediction window Maps menu, the terminals and date you specified for the prediction, along with the current time, will be used.

The rectangular map is centered horizontally on the longitude of your default terminal. The great circle map, more technically known as an azimuthal equidistant projection, is centered on the geographic (latitude and longitude) location of your default terminal.

Both maps display the great circle passing through Terminals A and B, and the terminator (gray line). The terminator is the great circle separating the sunlit side of the Earth from the dark side. An eight-pointed solar icon indicates the subsolar point on the surface of the Earth. The boundaries of the polar areas in which polar cap absorption (PCA) events occur are shown surrounding the north and south poles on both maps. Increased absorption may greatly reduce received signal levels during PCA events on paths passing through these polar areas.

The great circle map has the property that the great circle path from the center of the map to any other point on the map is a straight line, and the distance scale along this straight line is linear (constant). Azimuths (bearings) from the map center to any other point are correctly represented. The circumference of the map is the antipode of the center, and may be reached by traveling along a great circle at any azimuth from the center. W6ELProp uses a proprietary plotting method that correctly plots features near the antipode.

W6ELProp will print a great circle map centered on any location you specify; see

Print Great Circle Map.

New Date

New Time

Now

Auto Update

Close

Closes the map and returns to the W6ELProp Main Menu or to the Prediction window.


Rectangular and Great Circle Map Dialog Box

When you choose Rectangular Map or Great Circle Map from the Maps menu on the W6ELProp Main Menu Bar, you will use the Rectangular and Great Circle Map dialog box to specify the parameters needed to display the chosen map.

Terminal A and Terminal B

The great circle path will be drawn on the map between the terminals you specify.

Date

Enter the date for which you want the terminator (gray line) to be drawn.

Time

Enter the four-digit time for which you want the terminator (gray line) to be drawn.

OK (F9)

This will start the calculation and display of the map. You may also press the F9 key.

Cancel

Return to the W6ELProp Main Menu.

Entering Terminal Data

Entering the Date


Graphs

This menu at the top of the W6ELProp prediction window allows you to view graphs of the MUF or signal (signal level or signal-to-noise ratio) predictions.

MUF Graph

Signals Graph


MUF Graph

This choice in the Graphs menu at the top of the W6ELProp prediction window allows you to view a graph of predicted MUFs. The MUFs are plotted for every half hour of the day.

A button below the graph allows you to toggle the graph between a display of short-path and long-path predicted MUF.

Print


Signals Graph

This choice in the Graphs menu at the top of the W6ELProp prediction window allows you to view graphs of predicted signal levels and signal-to-noise ratios.

The predictions are displayed for all of your prediction frequencies; a different color code is used for each frequency. The predicted mode availability is indicated by the symbols used to plot the predicted signal level or signal-to noise ratio. Signal display is suppressed if the predicted availability is zero and you have chosen to suppress zero-availability predictions, or the predicted signal level is below the suppression threshold you have specified.

Click a curve to identify its frequency.

A button below the graph allows you to toggle between a graph of signal levels and a graph of signal-to-noise ratios. Signal-to-noise ratios are calculated as described under W6ELProp Prediction Window.

Another button allows you to toggle the graph between a display of short-path and long-path predictions.

Print


Advanced Prediction Window

This window appears when you choose Advanced on the menu bar of the W6ELProp Prediction window. It provides information that supplements and expands the predictions in the W6ELProp prediction window. You can choose to group the scrollable information by prediction frequency or time of day, and to display the predicted information for either the short or long path.

The predicted ionospheric hop configuration (combination of E- and F-layer hops) is shown at each time and frequency for the mode that yielded the strongest signal level. The hops are always shown in sequence along the path starting from Terminal A. Each dash (–) in the hop configuration indicates the ground reflection between the adjacent ionospheric reflections. You will find it instructive to scroll through the configurations and see how the ionospheric modes change through the day on the selected frequencies. The dominant mode at the higher frequencies is usually the lowest-order F-layer mode, but at the lower frequencies E-layer hops are often included and the radiation angle may be either lower or higher than for the lowest-order F-layer mode.

The predicted availability percentages are expressed as a decimal number (as opposed to the quartile indices given by the letters A through D).

The radiation angle associated with each hop configuration is also given.

The predicted MUFs and signal information shown in the prediction window are also displayed here; you do not have to refer to the prediction window for this information, and you do not need to toggle between signal levels and S/N because they are both shown.

File

Info


Printing Predicted Information

The Print command is available in the File menu on the menu bar of some of the windows that display predicted information. When available, this command allows you to send the information in the window to your printer. Except for the Signals Graph, all printing is in monochrome.

The Signals Graph requires a color printer. It may also require more memory than is available in your printer; you can minimize the memory requirement by setting your printer for its minimum resolution.

Note that when printing the Advanced Prediction window, the printed output can exceed 300 lines. For all other windows, the printed output will be on one page.


Options

There are several values and settings (e.g., frequencies) used in W6ELProp that you can set or change to satisfy your needs. These values and settings are called defaults. Choose Options on the W6ELProp Main Menu Bar to view, set, or change the defaults.

The defaults are grouped on four notebook pages.

Default Terminal

Frequencies and Constants

Prediction Parameters

User Preferences

Save My Settings and Exit

Click this button to save your settings and exit Options.

Cancel

Exits Options and nullifies any changes you may have made.


Default Terminal

There is probably a location you will use most often as a terminal when running a W6ELProp prediction or viewing the maps. You can save the parameters of this location as the default terminal. Then when you want to use this location as a terminal it will only be necessary to specify that the default terminal be used when you are prompted for the prefix of the terminal; you will not have to enter the latitude, longitude, and name each time.

Terminal Name

The name may be a call sign, city name, or any other combination of up to 17 characters.

Latitude, and Longitude

The latitude and longitude should be entered as described in About Latitudes and Longitudes.

When you have finished setting the default terminal, you can select another Options page or click Save My Settings and Exit to exit. Click Cancel to cancel your changes.


Frequencies and Constants

W6ELProp propagation predictions are initially for the frequencies of 3.6, 7.1, 14.1, 21.2, and 28.3 MHz. You may change these frequencies, delete frequencies, or add frequencies to any combination of up to ten frequencies between 3 and 30 MHz. This will allow you to add frequencies in the 12-, 17-, and 30-meter bands or in the shortwave broadcast bands, for example.

You may specify for each frequency an additive constant that will be included in all predicted signal levels for that frequency. For example, if 14.1 MHz is one of the frequencies you have specified, and if you want the signal level predictions for this frequency to be based on a transmitted power of 1000 watts instead of the built-in value of 100 watts, you would specify an optional constant of 10 dB for signal level predictions at 14.1 MHz. If, in addition, you want the prediction to take into account a yagi antenna with 6 dB gain over a half-wave dipole at one end of the path, increase the optional constant to 16 dB.

The original default value of the additive constant is 0 dB. You may change it to any value between –99.9 dB and +100 dB. Negative values might result from a transmitted power less than 100 watts or an antenna gain less than that of the assumed half-wave dipole.

All the current prediction frequencies are listed in one column and their associated constants in a second. Selecting (highlighting) a frequency will cause its associated constant to also be selected, and vice versa.

Add Frequency

Click this button to add a frequency and an associated constant.

Delete x.x MHz

In the frequency list, click on a frequency to select it for deletion. Then click this button.

Modify Constant

To modify a constant, select the constant and click Modify Constant.

Restore Factory Frequencies and Constants

Clicking this button will delete all current frequencies and constants, and restore the original frequencies and constants.

When you have finished making your changes, you can select another Options page or click Save My Settings and Exit to exit. Click Cancel to cancel your changes.


Prediction Parameters

Default prediction parameters define the way predictions are calculated and displayed. The parameter values displayed before you make any changes are those currently in effect.

Minimum Radiation Angle

The minimum usable antenna radiation (elevation or take-off) angle depends primarily upon antenna height, terrain slope, and horizon obstructions. In the propagation predictions and Frequency Map, W6ELProp assumes this minimum angle to be 1.5 degrees unless you change it. You may change the antenna minimum radiation angle to any value between 0 and 45 degrees.

W6ELProp uses the value you enter as the starting point when searching for the ionospheric mode that yields the strongest signal. If you specify too great a minimum radiation angle, the number of hops on a given path may be excessive. In this case, a screen message will advise you that the prediction computation has been aborted.

It is recommended that you not specify a value appreciably below the radiation angle of the main lobe of your antenna if this would correspond to an antenna gain more than a few dB below the peak of the main lobe. Particularly on the lower frequencies—especially on 80 meters—this might cause the mode-searching algorithm to find a mode at an unrealistically low radiation angle; this would result in a predicted signal level that is unrealistically high.

Noise Bandwidth

Signal-to-noise predictions are calculated relative to the galactic and man-made noise in the bandwidth you specify here. The original default value is 1 Hz, but you can specify any value between 1 Hz and 20,000 Hz.

Signal Level Suppression Threshold

Signal levels below –10 dB with respect to 0.5 microvolt are normally not reported when you run a prediction because weaker signals are generally unusable. However, W6ELProp allows you to specify a different threshold. You may set the suppression threshold to 0, –10, or –20 dB, or you may completely eliminate suppression of the output of low signal levels. Keep in mind that the time required to compute a prediction will usually increase when the suppression threshold is lowered or eliminated.

Man-Made Noise Environment

Signal-to-noise predictions are calculated relative to received galactic and man-made noise. You may choose among four levels of man-made noise. The industrial noise level is the highest, and will result in the lowest S/N predictions. Remote is the lowest level, but is seldom encountered.

Availability Suppression

Signal level and signal-to-noise ratio predictions are normally suppressed (not shown) when the predicted availability is zero for the strongest mode. Click the check box to remove or add the check mark. Zero-availability suppression is in effect when checked.

Restore Factory Prediction Parameters

Clicking this button will cause all prediction parameters to revert to their original settings.

When you have finished making your changes, you can select another Options page or click Save My Settings and Exit to exit. Click Cancel to cancel your changes.


User Preferences

User preference settings allow you to control several of the ways in which you interact with W6ELProp. The settings displayed before you make any changes are those currently in effect.

Primary Solar Index

When you run a prediction or use the Frequency Map, you have to enter a solar index—either a sunspot number or solar flux value. You tell W6ELProp you are entering a sunspot number by preceding the value with the letter S, or that you are entering a solar flux value by preceding the value with the letter F. But if you expect to use one index more often than the other, you can designate that index as your primary index; then you will not have to use the prefix letter when entering values of that index. For example, if you select solar flux as your primary index, you will be able to enter a solar flux value of 95 as either F95 or simply 95. In this case, you will still be able to enter sunspot numbers, but they will have to be preceded by the letter S.

Primary Signal Display

When you run a W6ELProp prediction, predicted signal levels are normally displayed first, and you can then click a button to toggle to a display of signal-to-noise ratios. If you wish, you may select signal-to-noise ratios for the primary display, and then click a button to toggle to the display of signal levels.

Time Display

Times of day are normally entered and displayed in W6ELProp in Universal Coordinated Time (UTC). You can choose User Local Time (ULT) if you want times to be entered and displayed in your local time. W6ELProp obtains both UTC and ULT from Windows, so be sure you have correctly set your time zone, time and date in Windows’ Date/Time Properties dialog box. Sunrise, sunset and other time-related calculations in W6ELProp also use your settings.

Map Auto Update Interval

The W6ELProp map displays can be set to automatically redraw themselves with the current date and time after a fixed number of minutes. You can set the update interval to any integer number of minutes between 1 and 60.

Frequency Map Resolution

The Frequency Map suggests which of your prediction frequencies is most likely the best to use at any time of day to communicate with each of several areas of the world. If you choose Low resolution, the calculations are made to 57 areas of the world, or to 877 areas if you choose High resolution. The calculation takes about fifteen times longer in high resolution than in low resolution.

Restore Factory Preferences

Clicking this button will cause all user preference settings to revert to their original values.

When you have finished making your changes, you can select another Options page or click Save My Settings and Exit to exit. Click Cancel to cancel your changes.


Operating Aids

The commands in the Operating Aids menu on the W6ELProp Main Menu Bar allow you to print two operating aids for use in your station.

Print Great Circle Bearings

Print Great Circle Map


Print Great Circle Bearings Dialog Box

You will use this dialog box to give W6ELProp the information it needs to print the table of great circle bearings.

Name

Enter the text that will appear in the “From” label at the top of the table.

Latitude

Enter the latitude of the location from which the bearings will be calculated.

Longitude

Enter the longitude of the location from which the bearings will be calculated.

Minimum Font Size

Specify a point size between 6 and 12 points for the printed table. (Newspaper type is typically 8-point.) If a larger point size than you specify can be used without increasing the number of pages, the larger size will be used automatically. Therefore, the point size you specify is a minimum.

Print Table Alphabetically by

You can choose to have the table printed alphabetically by the prefixes or names (locations) of the atlas entries.

Print

Click this button when you have entered the required information and you have readied your printer.

About Latitudes and Longitudes


Print Great Circle Bearings

This choice is available in both the Atlas menu and the Operating Aids menu on the W6ELProp Main Menu Bar; it allows you to print a customized table of great circle bearings (beam headings) from any location to all the locations in the W6ELProp atlas. The heading and first few entries of a column in the printed table will resemble this:

PREFIX LOCATION          DEG

1A0    S.M.O. of Malta    34

1S     Spratly Is.       302

3A     Monaco             36

You may choose to have the entries printed in alphabetical order of prefix or name (location). (ASCII alphabetization is used. Numerals precede letters. The numeral 0 precedes the numeral 1.) The bearings are measured in degrees east of north, and are in the range 0 through 359 degrees. However, if the location you specify is at either the north or south pole, the west longitudes (0 through 359 degrees) of the atlas entries are printed in the DEG column. Three asterisks (***) are printed in the DEG column if the specified location and an atlas entry are collocal or when they are antipodal (diametrically opposite each other).

Print Great Circle Bearings Dialog Box


Print Great Circle Map Dialog Box

You will use this dialog box to specify the location on which the map will be centered.

Name

Enter the text that will appear in the “This map centered on” label at the bottom of the map.

Latitude

Enter the latitude of the location at the center of the map.

Longitude

Enter the longitude of the location at the center of the map.

Print

Click this button when you have entered the required information and you have readied your printer.

Note that this map may require more memory than is available in your printer. You can minimize the memory requirement by setting your printer for its minimum resolution.

About Latitudes and Longitudes


Print Great Circle Map

This choice is available in both the Maps menu and the Operating Aids menu on the W6ELProp Main Menu Bar; it allows you to print a great circle map centered on any location you specify. The map will be printed in monochrome.

Print Great Circle Map Dialog Box


Add Atlas Entry Dialog Box

You will use this dialog box to add an entry to the W6ELProp atlas. The atlas can hold 1364 entries.

Prefix

Enter the prefix for this new atlas entry. Prefixes may contain from one to six characters. Country prefixes, call area prefixes, station call signs, or any other unique identifier may be used. Spaces are not allowed and you will not be allowed to enter an all-numeric prefix. No punctuation marks are allowed other than a single embedded /. W6ELProp will check to make sure the new prefix is not already in the atlas.

It is recommended that you not enter a prefix having the format of an IARU Locator (two letters followed by two numeric digits and an optional two additional letters). If you do, you will not be able to use this entry as a Locator.

Latitude

Enter the latitude of the new atlas entry.

Longitude

Enter the longitude of the new atlas entry.

Name

The name may be a country name, city name, call sign, or any other combination of characters not exceeding 17 characters in length.

Add Entry

Click this button when you have entered the information for this new atlas entry.

About Latitudes and Longitudes


Modify Atlas Entry Dialog Box

You will use this dialog box to modify an existing entry in the W6ELProp atlas.

Current Entry Prefix

Enter the prefix of the atlas entry you want to modify. W6ELProp will then display the current contents of the entry, and the insertion point will move to the right side of the dialog box so you can modify the contents of the entry.

Modified Entry Prefix

Enter the prefix of the modified atlas entry if different from the current entry prefix. Prefixes may contain from one to six characters. Country prefixes, call area prefixes, station call signs, or any other unique identifier may be used. Spaces are not allowed and you will not be allowed to enter an all-numeric prefix. No punctuation marks are allowed other than a single embedded /. W6ELProp will check to make sure the new prefix is not already in the atlas.

It is recommended that you not enter a prefix having the format of an IARU Locator (two letters followed by two numeric digits and an optional two additional letters). If you do, you will not be able to use this entry as a Locator.

Modified Entry Latitude

Enter the latitude of the modified atlas entry if different from the current entry latitude.

Modified Entry Longitude

Enter the longitude of the modified atlas entry if different from the current entry longitude.

Modified Entry Name

Enter the name of the modified atlas entry if different from the current entry name. The name may be a country name, city name, call sign, or any other combination of characters not exceeding 17 characters in length.

Modify Entry

Click this button when you have finished modifying the information for this atlas entry.

About Latitudes and Longitudes


Delete Atlas Entry Dialog Box

You will use this dialog box to remove an entry from the W6ELProp atlas.

Prefix

Enter the prefix of the atlas entry you want to delete. W6ELProp will then display the current contents of that entry.

Find In Atlas

Click this button if you need to locate the entry in the atlas.

Delete Entry

Click this button to remove the displayed entry from the atlas.


The W6ELProp Atlas

The W6ELProp atlas contains the latitudes and longitudes of DXCC entities and other locations. Each atlas entry contains a unique prefix, a name for the location, and the latitude and longitude of the location. The atlas entries can be accessed by prefix or name. The W6ELProp atlas is contained in a file, W6ELProp.ATL, that is created when you first run W6ELProp.

Replacing the W6ELProp Atlas

If you wish to use a MINIPROP PLUS atlas that you have customized for your needs, you cannot simply rename it from MPP.ATL to W6ELProp.ATL because the two files are formatted differently. Instead, place the MPP.ATL file in the same folder (directory) with W6ELProp.EXE (usually C:\Program Files\W6ELProp Propagation Prediction); then rename W6ELProp.ATL to W6ELProp.ATX. When you start W6ELProp, it will generate a new W6ELProp.ATL file from the information in MPP.ATL. W6ELProp.ATX will remain in the folder.

If W6ELProp cannot find either a W6ELProp.ATL or MPP.ATL file, it will use information built into the program to create a new W6ELProp.ATL.

Viewing the Atlas

The View command in the Atlas menu on the W6ELProp Main Menu Bar allows you to view the entries in the W6ELProp atlas. You can toggle between viewing the atlas entries alphabetically by prefix or by name. (ASCII alphabetization is used. Numerals precede letters. The numeral 0 precedes the numeral 1.) The prefix, name, latitude, and longitude will be displayed for each entry. To search quickly for a specific prefix (if viewing by prefix) or name (if viewing by name), type the prefix or name; the display will scroll as you type.

Editing the Atlas

The Edit command in the Atlas menu on the W6ELProp Main Menu Bar allows you to add, modify, or delete an entry in the W6ELProp atlas.

Add Atlas Entry

Modify Atlas Entry

Delete Atlas Entry

Print Great Circle Bearings


Fundamentals of Ionospheric Propagation

The several gaseous constituents of the upper atmosphere selectively absorb solar extreme ultraviolet light and X-rays, ion-electron pairs being produced in the process. The ionosphere is that region of the atmosphere in which the resulting free electrons exist in sufficient abundance to affect the properties of electromagnetic waves that are propagated through it. For practical purposes, the ionosphere can generally be assumed to extend from about 50 to roughly 2000 km above the surface of the Earth. The structure of the ionosphere is highly variable, and this variability is imparted onto signals propagated through it. The ionosphere is divided into three regions--D, E, and F in order of increasing altitude and electron density. The regions are commonly referred to as layers.

The D region extends in altitude from 50 to 90 km. The electron density in the region has large diurnal variations that are highly dependent upon solar zenith angle. The electron density is highest near local noon, is higher in summer than in winter, and is lowest at night.

The E region spans the altitude range from about 90 to 130 km. The maximum density occurs near 100 km, although this height varies with local time. The diurnal and seasonal variations of electron density are similar to those of the D region. Collisions between electrons and neutral particles, while important in the E region, are not as numerous as in the D region. The E region acts principally as a reflector of HF waves, particularly during daylight hours.

Embedded at times within the E region is the so-called sporadic-E layer. This layer is an anomalous ionization layer that assumes different forms—irregular and patchy, smooth and disklike—and has little direct dependence on solar radiation. Sporadic-E ionization is believed caused primarily by wind shear, but the causes are not fully known. The properties of the sporadic-E layer vary substantially with location and are markedly different at equatorial, temperate, and high latitudes. Short-skip openings, sometimes on an otherwise dead band, are often a result of one-hop sporadic-E ionization. When sporadic-E ionization is sufficiently widespread, multi-hop propagation is possible. W6ELProp predictions do not include the effects of sporadic-E ionization.

The highest ionospheric region is termed the F region. The lower part of the F region, from 130 to 200 km, is termed the F1 region, and the part above 200 km is termed the F2 region.

The F1 region, like the E region, is under strong solar control. It reaches a maximum ionization level about one hour after local noon. At night and during the winter the F1 and F2 regions merge and are termed simply the F region. When the F1 region exists as a separate region, its effects on radio waves are very similar to those of the E region. The F1 region is not treated separately in W6ELProp.

The F2 region is the highest ionospheric region, usually has the highest electron density, and is the region of greatest value in long-distance HF ionospheric propagation. The region exhibits large variability in both time and space in response to neutral winds and electrodynamic drifts in the presence of the Earth’s magnetic field. The maximum electron density generally occurs well after noon, sometimes in the evening hours. The height of the maximum ranges from 250 to 350 km at mid-latitudes to 350 to 500 km at equatorial latitudes. At mid-latitudes, the height of the maximum electron density is higher at night than in the daytime. At equatorial latitudes, the opposite behavior occurs.

Electromagnetic waves are refracted when passing through an ionized medium, the refraction increasing with increased electron density and decreasing with increase of frequency. If the refraction is large enough, a wave reaching the ionosphere is bent back toward Earth as though it had been reflected, thereby permitting reception of the wave at a large distance from the transmitter. The F2 layer is the most important in this regard because of its height and its high electron density. The maximum Earth distance traversed in one F2-layer hop is about 4000 km. Round-the-world communication can occur by way of multiple hops.

If the frequency is too high, the wave is not refracted sufficiently to return to Earth. The maximum frequency for which a wave will propagate between two points is called the maximum usable frequency (MUF). Waves at low radiation angles require less refraction to return to Earth than do waves at high radiation angles. Consequently—for a fixed reflection point—MUFs are higher on longer hops because radiation angles are lower. The shortest distance along the Earth’s surface that can be reached by a refracted wave at a given frequency is called the skip distance. To reach shorter distances, lower frequencies must be used. The highest frequency at which a wave will be returned to Earth at vertical incidence (zero ground distance) is called the critical frequency.

Signals on their way to or from the F2 layer must pass through the E layer. The E layer is also capable of reflecting HF signals, and if the E-layer MUF is too high, the signals to or from the F2 layer are cut off or blocked. Signals can propagate between two points on Earth via the E layer in the same manner as they do via the F2 layer, but the maximum Earth distance traversed in one E-layer hop is only about 2000 km, so a significantly greater number of hops are usually required on DX paths.

Propagation between two points can occur via one or more F2-layer (henceforth referred to as F-layer) hops, one or more E-layer hops, or via a combination of E- and F-layer hops, with a ground reflection between adjacent hops. These three types of hop configuration, or mode, are referred to as F-layer modes, E-layer modes, and mixed modes.

Because of the large variability that exists within the ionosphere, predicted MUFs on a path between two points on the Earth are not absolute limits, but are statistical in nature. The actual MUF at any given time may be higher or lower than the predicted MUF. Predicted MUFs are intended to be median values; i.e., the actual MUF will exceed the predicted MUF 50 percent of the time, and will be less than the predicted MUF 50 percent of the time. The predicted frequency that will be supported by the ionosphere only 10 percent of the time is a frequency higher than the predicted MUF. This frequency is called the highest probable frequency (HPF), but even higher frequencies are possible 10 percent of the time. The predicted frequency that will be supported 90 percent of the time is a frequency lower than the predicted MUF that is called the optimum traffic frequency (FOT, from the French Frequency Optimum de Travail).

The D region of the ionosphere must be traversed by signals from or to the Earth on their way to or from the F or E layers. Electron densities in the D region are not large enough to cause HF signals to be returned to Earth, but the high collision frequency between electrons and neutral particles in the D region causes absorption of signals passing through it. The reduction of signal strength can be substantial, particularly in daytime in the lower HF range.

Electron density in the ionosphere increases with increased radiation of extreme ultraviolet (EUV) light and X-rays from the sun. Therefore, MUFs and signal absorption both increase as these ionizing radiations increase. Unfortunately, these radiations cannot be measured directly, except by satellite-borne instruments, because they do not penetrate to the surface of the Earth. The sunspot number and solar flux are used as indirect measures of the ionizing radiations. The Zurich smoothed mean sunspot number has been used extensively as an index of solar activity and is the index with which propagation data has been correlated over the years. Therefore, most propagation prediction models require that the user specify the sunspot number to be used in making a prediction. The 2800-MHz (10.7-cm) solar noise flux is generally considered a more dependable indirect measure of the solar EUV and X-rays, but with a smaller base of propagation observations. Smoothed (12-month running average) values of the two indices are highly correlated, and W6ELProp allows you to specify either sunspot number or solar flux as a measure of solar activity.

Ionospheric propagation is susceptible to several kinds of short-term disturbance. These disturbances upset the electron configuration in the ionosphere, and consequently affect propagation. A sudden ionospheric disturbance (SID), sometimes called a shortwave fadeout (SWF), occurs when X-rays, emitted by a solar flare and traveling at the speed of light, reach the sunlit portion of the D layer, increasing the electron density—and thereby the absorption—by that layer. SIDs may last from a few minutes to as long as several hours. A polar cap absorption (PCA) event occurs as a result of intense ionization of the polar ionosphere caused by high energy protons from some large solar flares. PCAs start about 15 minutes to several hours after the protons are ejected by the sun, and last from about an hour to 60 hours or more. Ionospheric storms are caused by lower energy protons from disappearing filaments, coronal holes, coronal mass ejections, and solar flares. These protons take from about 20 hours to about 60 hours to reach the Earth, and the corresponding storms last from a few hours to several days. Except for the tendency of some of these disturbances to recur in synchronism with the approximate 27-day rotation period of the sun, they are difficult to accurately predict and to quantify.

Ionospheric storms occur in conjunction with geomagnetic storms, and geomagnetic field disturbances can be used as an indicator of ionospheric disturbances. The severity of magnetic disturbances is indicated by the A and K indices that are included in the Geoalert voice announcements on WWV and WWVH, and that are also available from several sources on the Internet. In general, MUFs decrease and signal absorption may increase as geomagnetic field activity increases, although MUFs sometimes increase. Ionospheric and magnetic disturbances are often accompanied by visible auroras.

Propagation sometimes occurs by way of backscatter and on bent paths that are not great circle paths. Propagation only along great circle paths is considered in W6ELProp. Ionospheric ducting also is not considered in W6ELProp.

More information about ionospheric propagation can be found in Davies, K., Ionospheric Radio, Peter Peregrinus Ltd., 1990.


Frequency Map Dialog Box

You will use the Frequency Map dialog box to specify the parameters needed to display the Frequency Map.

Terminal A

MUFs on the paths to the several areas of the world will be calculated for paths originating from Terminal A. See Entering Terminal Data.

Date

Enter the date for which you want the path MUFs to be calculated. See Entering the Date.

Time

Enter the four-digit time for which you want the path MUFs to be calculated.

Solar Index

Enter the sunspot number or solar flux. See Entering the Solar Index.

K Index

Enter the K index. See Entering the K Index.

OK (F9)

This will start the calculation and display of the Frequency Map. You may also press the F9 key.

Cancel

Return to the W6ELProp Main Menu.


W6ELProp Frequency Map

See also Frequency Map Dialog Box

The Frequency Map suggests which of your prediction frequencies is most likely the best to use at any time of day to communicate via the short great circle path from a terminal you specify (Terminal A) to each of 57 areas in the world (low resolution) or 877 areas (high resolution). The Options choice in the W6ELProp Main Menu allows you to change the resolution.

The 57 (or 877) areas are of roughly equal size on the surface of the Earth and are rectangular in shape in the Frequency Map display. W6ELProp computes the predicted MUF from Terminal A to the center of each area. It then fills each area with a dot pattern indicating the highest of your prediction frequencies that is at or below that MUF. The indicated frequency in each area is usually the best frequency to use at the specified time because signals at higher frequencies have a lower probability of propagating, and absorption loss will be greater for signals at lower frequencies.

Click an area to see the highest available frequency in that area.

The dot pattern corresponding to each frequency is shown on the left side of the display. If you have set more than seven prediction frequencies, only the highest seven are used. The density of the dot patterns increases with increasing frequency, so the brightest parts of the display will indicate the areas to which the MUF is the highest. The absence of a dot pattern in any area indicates that the predicted MUF to that area is below all your prediction frequencies (or below the highest seven if you have set more than seven prediction frequencies).

If you want the map to display only the areas to which one of your prediction frequencies is the highest frequency at or below the MUF, click on the box for that frequency on the left side of the screen. A button will appear below the boxes; click on this button to return to the display of all your prediction frequencies.

If you have deleted all prediction frequencies, W6ELProp will assume a frequency in each of the 10-, 15-, 17-, 20-, 30-, 40-, and 80-meter amateur bands.

Keep in mind that MUFs to different locations within the same area can differ. However, the areas are sufficiently small that this effect will be minor, and the predicted MUF computed to the center of each area will be representative of the MUF to any point within the area.

If you use high resolution (877 areas), the Frequency Map may show multiple skip zones in rings around Terminal A. These skip zones, other than the first, generally will not appear in practice because the actual ionosphere contains irregularities as opposed to the smooth gradients assumed in ionospheric models.

The eight-pointed solar icon is shown at the subsolar point. The small plus sign marks the location of Terminal A. Terminal A need not be your default terminal. You can specify any location on Earth for Terminal A, and the indicated frequencies will then be for paths from that location to the centers of each of the areas.

New Date

New Time

Now

Auto Update

Close

Closes the Frequency Map and returns to the W6ELProp Main Menu.


New Date

Allows you to change the date for which the map is drawn. The time will remain unchanged.


New Time

Allows you to change the time of day for which the map is drawn. The date will remain unchanged.


Now

Redraws the map with the current date and time.


Auto Update

Redraws the map with the current date and time. The map will repeatedly update after a predetermined number of minutes. The Options choice in the W6ELProp Main Menu allows you to change the update interval.


File

The Exit command is the only command in the File menu on the W6ELProp Main Menu Bar.


File

The commands in the File menu allow you to close the current window and to send the contents of the window to your printer.

Print


Help menu

The following commands are included in the Help menu on the W6ELProp Main Menu Bar in the W6ELProp opening window.

Contents

Lists the major W6ELProp Help topics.

Search for Help On

Opens the Help Topics dialog with the Index tab selected.

How to Use Help

Opens the standard Windows Help dialog.

About W6ELProp

Shows W6ELProp version and copyright information.


W6ELProp Files

The W6ELProp distribution package includes three files:

•	W6ELProp.EXE is the W6ELProp executable file

•	W6ELProp.HLP is the W6ELProp help file

•	License.TXT contains, in plain text format, the License Agreement that is a part of this help file

If they do not already exist from a previous installation of W6ELProp, four additional files will be created when you run W6ELProp:

•	W6ELProp.ATL will hold your working atlas

•	W6ELProp.SAV will hold your default settings

•	W6ELProp.REC will hold the rectangular map centered horizontally on your default terminal

•	W6ELProp.GC will hold the great circle map centered on your default terminal

In addition, you may print on-screen predictions to disk files (default extension TXT), batch predictions to disk files (default extension WPF), and save Batch Tables in disk files (default extension WBT).

The files W6ELProp.DAT and W6ELProp.GEO that were distributed with earlier versions of W6ELProp are no longer needed because their contents are now built into the program.


License Agreement

1. LICENSE GRANT

Sheldon C. Shallon, W6EL, (the "AUTHOR") grants you a non-exclusive license to install and use the W6ELProp™ software program (the "SOFTWARE") for non-commercial purposes only, on any computer, as long as the terms of this agreement are respected. Businesses and government agencies should contact the AUTHOR to make licensing arrangements.

2. OWNERSHIP

The SOFTWARE is owned and copyrighted by the AUTHOR. Your license confers no title or ownership in the SOFTWARE and should not be construed as a sale of any right in the SOFTWARE.

3. COPYRIGHT

The SOFTWARE is protected by United States copyright law and international treaty provisions. You acknowledge that no title to the intellectual property in the SOFTWARE is transferred to you. You further acknowledge that title and full ownership rights to the SOFTWARE will remain the exclusive property of the AUTHOR, and you will not acquire any rights to the SOFTWARE except as expressly set forth in this license. You agree that any copies of the SOFTWARE will contain the same proprietary notices that appear on and in the SOFTWARE.

4. DISTRIBUTION

You may make as many copies of the SOFTWARE as you wish for non-commercial purposes only. Unmodified copies of the SOFTWARE installation package may be distributed without restraint provided that no charge is made for said distribution.

5. ADDITIONAL RESTRICTIONS

A. You shall not (and shall not permit other persons or entities to) sell, rent, lease, modify, translate, reverse engineer, decompile, disassemble or include in other software the SOFTWARE or any component thereof, or create derivative works based on W6ELProp.

B. You shall not (and shall not permit other persons or entities to) remove or obscure copyright, trademark or other proprietary notices or legends from any of the materials contained in the SOFTWARE package.

6. DISCLAIMER OF WARRANTY

A. The SOFTWARE and documentation are provided "AS IS" and the AUTHOR disclaims all other warranties and conditions, whether expressed, implied, or statutory, including, but not limited to, fitness for a particular purpose, conformance with description, and non-infringement of third party rights. The AUTHOR does not guarantee that this SOFTWARE is free from bugs or free from computer viruses.

B. To the maximum extent permitted by applicable law, in no event shall the AUTHOR be liable for any indirect, incidental, consequential, special or exemplary damages or costs incurred arising out of the use or inability to use the SOFTWARE, even if the AUTHOR has been advised of the possibility of such damages.

7. GOVERNING LAW

This license shall be construed, interpreted, and governed by the laws of the state of California.


terminal

One end or the other of a propagation path; a path termination.


mode availability

The probability that the associated frequency will be less than the maximum usable frequency (MUF) for the strongest ionospheric mode at that frequency; the probability that the mode will exist.


ionospheric mode

An ionospheric hop configuration (combination of E- and F-layer hops).


muf
maximum usable frequency (MUF)

The maximum frequency for which a wave will propagate between two points. Predicted MUFs are intended to be median values; i.e., the actual MUF will exceed the predicted MUF 50 percent of the time, and will be less than the predicted MUF 50 percent of the time.


gray line or terminator

The dividing line between the sunlit and the dark parts of the Earth.


mode-searching

The unique algorithm employed by W6ELProp that takes into account the D, E, and F layers of the ionosphere when computing predicted received signal levels. The algorithm searches through the potential ionospheric modes (combination of E and F hops) and finds the mode yielding the strongest received signal.


short path, long path

The short path is the shortest of the two great circle paths between two points on the Earth’s surface. The long path is the longest of the two great circle paths.


PCA event
polar cap absorption (PCA) event

Occurs as a result of intense ionization of the polar ionosphere caused by high energy protons from some large solar flares. PCAs start about 15 minutes to several hours after the protons are ejected by the sun, and last from about an hour to 60 hours or more.