XMWGUIDE.TXT
OPERATING MANUAL FOR XMW 
A PROPAGATION PREDICTION PROGRAM
BY WILLIAM ALSUP, N6XMW
INSTALLATION
1. Make sure that your version of DOS or Windows includes QBASIC.EXE. If not,
you will need to add QBASIC.EXE to run in the directory (c:\N6XMW) that will 
be created when installing XMW. QBASIC.EXE is not supplied on this CD-ROM, 
but you can generally find it on the Windows 95 or Windows 98 CD-ROM, 
usually in either the \Tools\OldMSDOS or the \Other\OldMSDOS subdirectories.
2. From the ACV6\N6XMW subdirectory, type INIT_XMW.BAT and if QBASIC is 
available, a short set of configuration questions will be asked during the 
initialization phase for XMW.  Please answer the questions.  
3. Then, you will automatically wind up at the XMW main menu where you will 
have ten options, accessible by function keys F1 through F10, each described 
below.  
4. Thereafter, you can always run XMW from the \ACV6\N6XMW directory by 
typing XMW.BAT.  You can also use your program manager to run XMW.BAT from 
the windows main screen.  
INTRODUCTORY NOTE ON NAVIGATION
You always start from the main menu and choose a subprogram with one of the 
function keys.  There is no mouse.  All commands are via the keyboard, 
usually (but not always) either a 0 (or simply Enter), or a 1 or 2.  
The prompts are usually printed in yellow so that your attention will be 
drawn to them right away.  
If you want to interrupt the program (although there is no need to do so), 
hit CTRL-BRK.  You can resume by simply hitting F5 or you can return to the 
main menu with SHIFT-F5.  Again, from the main menu, remember to use a 
function key (e.g., F1) to launch a sub-program.  
F1:  THREE-HOUR PROPAGATION FROM QTH1 TO TWENTY TARGETS 
FOR GIVEN DATE
This displays the openings (and non-openings) from a single QTH anywhere in 
the world to each of twenty targets.  By way of inputs, you can choose any of 
your home QTH's as the hub QTH or pick any place else as the hub.  You can 
use the actual date and/or UTC (in which case the display will continuously 
update as the clock ticks) or you can use an artificial date and UTC (in 
which case it will continuously re-run for the same date and time).  You must 
also input the antenna heights.  
After entering the inputs, the screen will generate and display the predicted 
propagation between the hub QTH and twenty pre-selected targets in the world.  
For each individual target, signal indices for 7, 14, 21 and 28 MHz, are 
calculated and shown in sets of three numbers.  The middle number is for the 
UTC on the screen, the left-hand number is for one hour earlier, and the 
right-hand number is for one hour later.  In turn, each number conveys three 
indicators, as follows:  
Strength:  The larger the number indicated, the better will be the signal.  
Any number under three will be unreadable above normal noise.  Nine is the 
highest number and is a very strong signal.  All numbers higher than nine are 
truncated to nine.  A four, five or six is a readable signal.  A three is 
borderline.  (The numbers do not necessarily correlate to S units.)  The 
strength is always based on the strongest open hop mode.  A hyphen means an 
opening is unlikely.  
To simplify presentation, XMW was calibrated to simulate the results (on 
approximate basis) obtained when both stations use 100 watts of power and a 
three-element tribander antenna.  If your station uses more or less power, 
then you have to adjust mentally.  
Reliability:  The color of the number shows its reliability (with one 
exception noted below).  Gray is 50-50.  Bright white is better.  Reliability 
is based on how close the strongest hop mode is to breaking through the F 
layer into outer space (and thus being lost), or to being screened by the E-
layer (and thus being lost).  For example, if the three-hop mode is the 
strongest, and it is right at the edge of passing through the F layer into 
space at one or more apexes, then it is 50-50 in terms of reliability.  
Alternatively, if that mode is almost screened by the E layer, then it is 50-
50.  If the strongest hop mode is close to the edge, then a check is made to 
see if the second strongest hop mode is almost as strong and is more safely 
within limits.  If not, then the 50-50 reliability is retained and indicated 
by displaying the strength in a gray color.  If the strongest mode or an 
almost-as-strong second mode is well within both limits, then it is more 
reliable and is shown as bright white.  Signal strength is independent of 
signal reliability.  It is entirely possible, for example, to have great 
strength with only 50-50 reliability.  A hyphen means no opening or the 
probability of an opening is less than 50-50.  
Fading:  When multiple modes are open, such as, for example, 3F, 4F and 5F, 
then the incoming modes will add or subtract in phase, at any given moment, 
depending on their relative phases.  Even though different hop modes may be 
open, their combined strengths may actually be less than the strength of the 
strongest standing alone.  As the ionosphere churns about, the path lengths 
of such modes vary.  In turn, their relative phase differences vary, which 
means fading.  If, after application of the vertical radiation patterns of 
both antennas, only one of the modes is clearly dominant, then fading will be 
negligible.  If, however, the second strongest mode is at least fifty percent 
as strong as the strongest mode, then the program assumes you will hear 
fading.  Alternatively, if the strongest signal is less than 50% of the total 
strength of all open modes, then the program also assumes you will hear 
fading.  In both cases, the program then places a "~" after the strength 
indication.  Thus, a number "7~" indicates a strong signal with noticeable 
fading (and its color will indicate its probability of being open).  As 
stated, the presumed signal strength is based only on the strongest of the 
hop modes.  (If there are other open hop modes, it is presumed that there 
will be fading of signal strength up and down but still centered about the 
strength of the strongest mode.  The fading indicator is shown in the VRP 
mode only.  It is not shown in the NO VRP mode because fading depends, in 
part, on how your VRP magnifies or suppresses the incoming hop modes.)  
If any significant chordal propagation is detected, then the resulting signal 
strength, even a hyphen, is printed in yellow.  This is the case for both 
true chordal and near-chordal propagation and both short path and long path.  
The foregoing predictions are refreshed and displayed in a continuous loop.  
You can alter the assumptions used without breaking the loop by hitting 
selected F keys.  F2 allows you to toggle between a VRP and a no-VRP 
assumption.  (VRP means Vertical Radiation Profile, uses a flat-earth 
horizontal orientation, and allows you to vary the antenna height and see the 
impact.)  F4 allows you to toggle between the short path and the long path.  
F5 allows you to toggle among the different sets of targets.  The starting 
group is a worldwide group, as stated.  The next set of twenty are in the 
Western Hemisphere only.  The next is for Europe and Africa.  After that is a 
group for the Pacific and Asia.  Then, there is a special long-path group.  
The final group is a North America group of twenty cities.  After that, it 
returns to the first group.  F3 allows you to interrupt the loop to adjust 
certain parameters, like the flux.  
The targets and the corresponding predictions occupy most of the screen but 
at the bottom of the screen are three side-by-side and different views of the 
globe (Polar, Pacific, Atlantic).  Each shows the current grayline and sun 
location, the yellow cross showing where the sun is directly overhead.  The 
opposite point on the earth is marked with dark blue cross.  These 
solar/grayline indications also update themselves on each loop.  
The other information on the screen is the month, date, UTC, declination, 
flux, K index, the presumed antenna heights, antenna gains and power (= 100 
watts always).  The local time at QTH2 is also shown in the far right column.  
Any local time between midnight and 6:00 a.m. is shown in dark blue to remind 
you that most hams there will be asleep.  The beam heading toward QTH2 is 
shown.  
Near the top of the screen is a guide to the F keys useable during the 
continuous loop.  To repeat:  
* F1:   This will return you to the main menu.  
* F2:   This will toggle between the VRP and No-VRP alternative assumptions.  
Comparing No-VRP with VRP allows you to see the effect of the vertical 
radiation profile.  
* Again, note when the VRP assumption is used, a horizontal antenna is 
presumed.  XMW does not yet involve a module for vertical antennas, although 
the NO-VRP alternative is still useful for determining whether an opening 
exists at all.  
* F3:   This will allow you to interrupt the loop temporarily to adjust the 
solar flux, K index, and the heights of the antennas.  
* F4:   This will toggle between the short and the long path.  Short is the 
default.  SP or LP will appear, as appropriate, on the screen.  
* F5:   This will advance to the next group of targets.  
F2:  24-HOUR PROPAGATION FROM QTH1 TO QTH2 FOR  GIVEN DATE
This option shows propagation measured at 24 even intervals over the course 
of a day for any given path and conditions.  You have three sub-choices, as 
follows:  
1.      Openings By Takeoff Angles and Strength.  
The first sub-option allows you to input a path (defined by any two locations 
on the globe) as well as a date, flux and K index.  The sub-program then 
constructs four separate graphs (one for each of 7, 14, 21 and 28 MHz), all 
on the same screen.  Each graph shows when the path is open and when it is 
not for each of the 24 hours of the date selected; if it is open, then the 
signal strength and takeoff angle is shown for each hop mode that is open.  
For each of the four graphs, the horizontal axis is UTC.  The vertical axis 
is the takeoff angle, from 0 to 50 degrees.  The vertical position of the 
square or pixel indicates the takeoff angle of the hop mode.  There will be a 
square for each hop mode that is open.  So its vertical position tells the 
takeoff angle.  The square size tells the strength.  A large square (one-
eighth inch square on a typical screen) is a loud signal but a small mark is 
not readable (over usual noise).  
The hop modes are color-coded.  The color code is in the upper left corner of 
the screen.  (Hop = 1 or 6 = Red; 2 or 7 = White; 3 or 8 = Magenta; 4 or 9 = 
Yellow; 5 or 10 and above = Green.)  When chordal propagation is indicated, 
however, the hop codes are obviously meaningless.  
Each graph has several cyan lines rising and falling from left to right, 
often overlapping, sometimes diverging.  These are the highest takeoff angles 
that the F layer will support using the conventional multi-hop model, one for 
each hop mode tested.  To see how close the takeoff angle is to the highest 
permissible takeoff angle for a hop mode, simply check to see how close the 
square is to the cutoff.  This allows you to gauge the reliability of the 
signal.  If it is close to the cutoff, then its reliability is only 50-50.  
If it is well within limits, it will be much more reliable.  
The green line represents the lowest possible takeoff angle that avoids E-
layer screening (allowing, at most, only one E-layer reflection).  There will 
be a green line for each hop mode.  These will almost always overlap with 
each other.  If the hop mode is close to this cutoff, then it is only 50-50 
reliable.  
The maximum and minimum takeoff limits are not color-coded.  An earlier 
version tried to do so.  It was confusing.  So now all the maximums are cyan; 
all the minimums are green.  By the way, why do the maximum takeoff angles 
differ from hop mode to hop mode?  Shouldn't all the highest angles be the 
same for a given frequency and time?  And, shouldn't all the lowest angles be 
the same for a given frequency and time?  At first glance, you would think 
so, but actually, as the hop modes change from, say, two-hop to three-hop, 
the relevant apexes on the great circle route change positions, thus possibly 
changing the weakest and strongest points of relevance in the F and E layers.  
With the sole exception of chordal effects, discussed momentarily, a mode is 
thus open only if its takeoff angle is between the upper and lower cutoffs 
for that mode, i.e., the takeoff angle is high enough to avoid E-layer 
screening but not so steep as to pierce the F layer.  Some paths will show 
very few open modes and others, many.  It just depends.  Some will show 
several different hop modes open at once, especially on 7 and 14 MHz.  
To determine if there will be fading, look at the open modes.  If the 
strongest is the most dominant by far and well within the maximum and minimum 
limits, then there will be little fading.  If there are two or more stronger 
modes roughly equal in strength, or several open modes with none clearly 
dominant, there will usually be fading.  
With respect to chordal propagation, a separate and supplemental graph is 
imposed on the 28 MHz graph (simply because it usually has the most extra 
room).  The supplemental graph shows the "tilt" factor in a dotted line 
format.  The higher it is, the better the chordal or near chordal 
possibilities.  The bottom or base of that supplemental graph is the solid 
yellow line.  Although it is superimposed on only the 28 MHz graph, the tilt 
factors apply to all of the frequencies, and all four graphs.  When chordal 
propagation is at work, it is entirely possible that the takeoff angle will 
exceed the cyan lines indicating the highest normal takeoff angles.  This is 
because chordal propagation allows higher takeoff angles than multi-hop 
propagation will normally support.  Because chordal propagation does not 
involve conventional hops, the hop color code is really irrelevant, although 
it is still displayed.  
The screen will first show the results of "no VRP" effect included.  You can 
then select the opposite assumption and get the results on a new set of 
graphs.  Then you can see the difference by toggling to the "Last Screen."  
One advantage of the VRP option is that you can visually see how the 
antenna/terrain affects the strength of the open modes.  
2.      Openings By Takeoff Angles and Strength Using Output Data Previously 
Generated.  
Just after you press F2, a second sub-choice allows you to construct the same 
type graphs but from results previously generated.  This is quicker, all of 
the number crunching having already been done.  The latter, however, is 
limited to the middle of whatever month you input now and, of course, is 
limited to the flux and K index previously assumed. Otherwise, this sub-
choice is similar to No. 1.  To use this sub-option, you must first generate 
and store the outputs via F6 or F7.  
3.      Openings By MUF and EMUF (Conventional Format).  
Sub-option 3 will display the output more in the traditional MUF and EMUF 
graph format.  One graph (not four) is constructed.  This looks the most like 
the traditional propagation prediction graphs in QST but there are some 
differences.  
Again, you input any path and conditions you wish.  The output shows the MUF 
(solid line) and EMUF (dotted line) for the hop mode with the fewest number 
of hops possible (say, 3-hop from the West Coast to Europe) and for the next 
three higher-hop modes (say, 4-, 5- and 6-hop).  Any higher order hop modes 
are usually irrelevant and are omitted.  If the MUF exceeds the EMUF for a 
hop mode, then there will be-for that hop mode-a possible opening for the 
frequencies in between.  The bigger the gap, the better will be the openings 
as a general rule, although this sub-option does not take absorption into 
account, so you cannot tell if the opening is weak or strong.  The hop modes 
are color-coded (for the number of hops) as per the legend on the screen.  At 
the top of the graph is a separate graph showing the tilt factor (as a dotted 
line).  The solid yellow line (superimposed on the 30 MHz line) is the base 
for the tilt graph.  The greater the tilt factor, the greater will be the 
enhancement to MUF.  Yes, the MUF is adjusted to reflect the tilt factor.  
(Unlike the takeoff angle format, signal strength and VRP are not shown.)  
How do the predictions compare to the propagation charts in the QST?  The 
answer is somewhat close but there are differences.  The EMUF line differs 
from the LUF (QST) line mainly in that the LUF (QST) line also takes into 
account noise variation around the globe (whereas XMW ignores noise).  XMW 
also gives the results for higher hop modes, which usually will be of more 
practical value since the lowest hop modes are usually too weak to work for 
antennas of ordinary height.  And, sometimes there is simply a difference in 
the MUF's predicted due to differences in methodology.  
Toggling And/Or Saving the Screen.  Once any graph is generated by the 
program, you will be asked if you want to toggle to the "last screen."  If 
you do, you can then toggle back and forth.  This allows handy comparisons.  
The current screen will be saved and so it can be recalled next time as the 
"last screen."  This function, however, is not permanent storage.  For more 
permanent storage, after the toggle opportunity, you will be asked if you 
want to save the screen (1 = yes) and, if so, what, if any, short comment you 
wish to superimpose on the screen saved; and what priority you wish to assign 
to the saved screen (0, lowest; 2, highest).  Lower priority screens will be 
overwritten first, once the limit of ten screens are saved.  
F3:  24-HOUR CRITICAL FREQUENCY FOR GIVEN LATITUDES
This draws graphs of the F-layer vertical critical frequency and the center 
actual heights of the F layer at latitudes you designate, given a date and 
flux you input.  Data for four different latitudes can be drawn 
simultaneously for comparison.  The tick marks indicate the sunrise and 
sunset points.  The left side of each graph is longitude 0 at UTC = 0000.  
The last screen and screen-save functions work as in F2.  
F4:  CRITICAL FREQUENCY MAP OF THE WORLD
This draws a contour map of the world showing the estimated F-layer critical 
frequencies (at vertical incidence) as contours in increments of 1 MHz.  The 
inputs are a date, time and solar flux.  The contour lines are color-coded as 
per the legend on the screen.  The cyan line is 10 MHz, a convenient 
reference line.  The last-screen and screen-save functions work as in F2.  
F5:  GRAPH OF CRITICAL FREQUENCY
This sub-program graphs the critical frequency of the F layer (at vertical 
incidence) along the great circle path between any two end points.  By 
following the prompts, you can select any two end points in the world, any 
date, any UTC, any smoothed solar flux, and the long path or the short path.  
The route is divided into thirty segments of equal length and readings are 
taken at the 31 points thereby created (counting the ends too).  These 
readings are drawn on the screen.  Blue indicates night.  Yellow indicates 
daytime.  The latitude of the reading is shown in red (and QTH1 is circled in 
cyan).  The critical frequency of the E layer at vertical incidence is drawn 
in green.  The actual height of the F layer is shown in magenta.  
This feature is particularly useful for seeing why a path is or is not open 
and for identifying chordal-propagation profiles.  The latter tend to be U-
shaped profiles in which the critical frequency is lowest in the middle of 
the route (but high enough to support refraction at a slight angle of 
incidence) and gradually rises to peaks near the ends of the routes.  Again, 
the last-screen and screen-save functions work as in F2.  
F6:  SINGLE RUN OF ONE PATH FOR FULL-YEAR X 24-HOUR PERIOD
This generates and stores propagation output data for a single path between 
any two QTH's in the world.  At the end, the results will be automatically 
displayed and the output data will be stored in a file.  Later on, you can 
again view the stored output via F2 (sub-option 2) or F8.  The purpose is to 
generate a permanent output file, whose content can be quickly displayed at 
any time, thus, avoiding the time required to crunch numbers.  
F7:  BATCH RUN OF 20 PATHS FOR FULL YEAR X 24 HOURS
This generates and stores propagation data for the 20 paths from your home 
QTH to the 20 targets on the leading list of targets used in F1.  This takes 
up to an hour or more to run, depending on the speed of your CPU.  You can 
view the results via F2 (sub-option 2) or F8.  Again, the purpose is to 
generate and to store a lot of data that can be quickly displayed.  
F8:  DISPLAY GRAPHS OF BATCH OR SINGLE RUN
This is one of two ways to view the outputs generated via F6 or F7, the other 
being F2 (Sub-option 2).  F8 shows the daily propagation for each of 24 hours 
between two end points for each of twelve months, using a date in the middle 
of each month.  This is great for seeing what months you should listen for 
selected targets and on what bands and at what times.  The X-axis shows 
months 1 to 12.  The Y-axis shows UTC (0 to 2400).  For each "cell" in the 
grid thereby created, there can be four possible rectangles, one for each of 
7, 14, 21 or 28 MHz, all side-by-side, each frequency with its own color.  
The area of the rectangle indicates the strength of the strongest open hop 
mode.  If the rectangle is solid in filled-in color, then the signal is more 
reliable; if it is hollow, then it is close to 50-50 (i.e., near a cutoff 
frequency).  No box at all means no opening or that one is less than 50-50.  
Remember that XMW does not take noise into account, so you must view these 
results with judgment.  The grayline positions of sunrise and sunset for both 
QTH's are superimposed.  
F9:  DISPLAY SAVED SCREENS
F9 allows you to view screens previously stored.  F9 first lists the prior 
screens you stored and allows you to select one to view.  Storage is limited 
to ten screens because each graphics screen takes a fair amount of disk 
space.  You can toggle among the ten saved screens.  Follow the on-screen 
instructions.  
When you originally save a screen, you will be asked for a priority.  Two is 
the highest (0 is the lowest).  The priority input determines the order in 
which saved screens will be erased to make room for future screens saved.  If 
all ten slots are designated in the same priority or higher than you specify, 
you will be given an opportunity to revise the priorities already in storage.  
F10:  ADJUST CONFIGURATION FILE
This allows you (1) to add, to subtract, or to modify your list of QTH1's, 
such as your home QTH and any others that you wish to treat as QTH1, like a 
DX expedition venue (you can have as many QTH1's as you want but one is 
sufficient) and (2) to change the difference in hours between UTC and your 
computer clock.  Normally, you will want to have the latter difference the 
same for all QTH1's you input since your computer clock is in one place, but 
the program allows you to associate any difference you wish for each QTH1 you 
input.  
CONCLUSION
XMW is the result of many nights, mornings and weekends of work.  It was a 
solo job.  Help me find the bugs and please suggest improvements.  



73,   Bill,   N6XMW
1120 Ashmount Avenue
Oakland, California  94610

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