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1987-10-20
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MAPPER2 .. A DX MAP DRAWING and Propagation Program
for IBM PC Compatibles with graphics capability.
Version 2.0
by
Dennis P. Murray
11165 McDonald Street
Culver City, Ca. 90230
CompuServ 72770,2765
20 October, 1987
This program, written for BASIC compilers such as MICROSOFT QUICK
BASIC or BORLAND TURBO BASIC, displays a map of the world centered on
a user-selectable QTH, and does propagation predictions based upon a
modified MINIMUF method. It shows the regions of sunlight and darkness
around the world, and updates these regions automatically at user-
specified time intervals. It can also accept arbitrary times and dates
at the user option. The program accepts DXCC prefixes or
latitude/longitude values for the DX location, draws the path from the
home QTH to that location, and displays the range, azimuth and wave
launch elevation angle from the home QTH. The user can select either
short or long paths; the sunspot number; antenna height, gain, and
polarization for both home QTH and DX station; transmit power; and the
minimum wave launch angle to be used for propagation prediction. The
propagation prediction gives the MUF (maximum usable frequency), LUF
(lowest usable frequency) based upon E-layer screening, and the
minimum number of F-layer hops for the minimum launch angle.
Predictions of signal strength are made for Ham Band frequencies which
include D-layer absorption, reflection losses, and transmit and
receive antenna losses due to ground plane reflection at low elevation
angles.
This program is written for IBM PC compatible computers with an
EGA Graphics capability and color display. The source code provided
could be modified by the user to use other graphics displays supported
by your BASIC compiler. The program runs quite quickly on an AT clone
with a hard disk and 640k of RAM, but it might be a 'dog' on a floppy-
only machine because it must read some long files for the map data.
The author does not intend to support this software, but is
simply releasing it into the public domain for non-commercial use by
HAMS who know what they are doing with their computer. The BASIC
source code is included for that reason.
The author encourages the distribution of this program to anyone
who might find it useful, or onto bulletin boards which deal with HAM
radio or shortwave listening. Please make sure to include ALL the
required files in any uploading however. These files are:
1- MAPPER2.BAS The Program Source Code
2- MAPPER2.EXE the Q-BASIC v3.0 executable code
3- MAPPER.ATL An Atlas of DXCC countries and their
latitudes, longitudes, and DX prefix.
This is an ASCII file ,sorted by prefix,
which can be added onto by the user with
a word processor or text editor.
4- MAPPER.DEF A short file used to store some default
values used by the program.
5- MAPPER.SCR A large file which is used to store and
retrieve the screen data for a world map
centered on the user's location. This
file is rewritten whenever the user
changes the 'Home' location. ( It is
interesting to view the world as seen
from DX locations.) This data is read
into a large array in memory to permit
rapid redrawing of the map as the sun
moves. The file is written into the
integer array NSTORE by BLOAD and BSAVE
commands. Because the program uses a lot
of memory to speed things up, this array
is DYNAMIC and does not generally reside
in the normal BASIC data segment. The
version of the program supplied for
Q-BASIC uses the CALL PTR86 subroutine
supplied by MICROSOFT, and this module
must be specified during the linking
process. In TURBO-BASIC the VARSEG
command can be used to find the array
segment used in lines 3120 and 12140.
6- MAPPER2.DOC This instruction file.
7- WORLDMAP.DAT A large ASCII file containing the
lat/lon of the world's borders. This is
used to recompute the map whenever the
map center point is redefined.
INSTRUCTIONS:
To run this program simply enter 'MAPPER2'. After an initial
message explaining the program is displayed, and you press any key to
proceed, you will be presented with a 7-choice initial menu which
allows you to change the default values of:
1- Sunspot number
2- Home QTH latitude and longitude
3- The time interval at which the daylight/darkness areas are
redrawn.
4- Home antenna height, gain, and polarization.
5- DX station antenna height, gain, and polarization.
6- Transmitter power output.
7- Minimum elevation angle for propagation predictions.
Pressing the appropriate number key will put up prompts to allow
changes to these variables, and will return you to this menu after a
change is entered. Pressing <ENTER> at the menu prompt will store
these new values in the MAPPER.DEF file and proceed on to the map
drawing.
The map drawing will first put up a blank box, then calculate the
position of the sun at the time and date currently held by the DOS,
draw the solar terminator ( it looks like a satellite ground trace ),
and color the sun-lit portions of the world in red. It will then go on
to draw the country boundaries, color the oceans blue, and color the
USA green. The land areas which are in darkness will show up in black.
The program may miss coloring part of the oceans blue because of the
position of the solar terminator blocking the PAINT commands used in
the subroutine at line 8000 ... . I got tired of adding ocean points
to this routine to cover all the contingencies.
After the map is drawn a Menu bar will appear on the bottom line of
the screen, with 9 choices selected by the function keys:
f1- Select DX Prefix.
You will be prompted to enter a DX prefix ( eg. ZS for
S. Africa ). The program will then search the DX atlas
for an occurrence of this prefix. It will display all
of the entries ( ie ZS1,ZS2,... ) that contain this
string and ask you to select one. If the number of
candidate entries is large you can simply <ENTER> to
continue the search.
When a selection is made the program will fetch
the location of the prefix, make a propagation
prediction for the currently selected date and time,
draw the path from your QTH to that location, and
display sundry useful information at the top of the
screen. On the left of the screen the signal strength
predictions will be shown for all Ham bands for which
the frequency is more than 80% of the lowest usable
frequency (LUF), less than 120% of the maximum usable
frequency (MUF), and whose predicted signal strength
is higher than -20dB relative to 0.5 microvolts into a
50 ohm receiver input.
For each band which meets these criteria I display the
frequency, the absorption losses (Labs), the ground
reflection losses (Lref), the transmit and receive
antenna losses due to ground reflection ( Ltx, Lrx ),
and signal strength ( Prcv ). The losses are given in
dB. The signal strength is given in dB relative to 0.5
microvolts into 50 ohms. This is about an S-1 signal
level for most Ham receivers, and S-9 usually
corresponds to 50 microvolts at the antenna terminals.
Thus a signal strength of 40 dB would correspond to a
S-9 prediction.
The user should be cautioned that the signal strength
predictions are very uncertain. I only calculate paths
via the F2 layer, and there a great number of other
propagation modes possible which may be better or
worse than the pure F2 mode. Don't blame the author if
this program says that you can't possibly work
Australia when you are hearing VK's with S-9 signals.
These are only crude indications of the likelihood of
a path being open.
f2-Specify Country Name.
Same as option 1 except that you are prompted for the
name of a country ( or a subset of that name such as
'AUS', which will find both Austria and Australia ).
The search process is insensitive to the case of your
entry.
f3-Specify Lat/Lon.
Same as the above option except you will be prompted
to enter the latitude and longitude of the desired DX
location.
f4-Select Date/Time.
Prompts for a new date and time to be used to
calculate solar terminator and make propagation
predictions. <ENTER> responses to either of these
prompts will fetch the current DOS value of date or
time. This option will also turn off the automatic
updating of the terminator and map redraw.
f5-Use Real Time.
This option will reset the above option to the real
(DOS) date and time and enable the auto update
feature.
f6-Select Short Path.
This toggles the path from the long path option back
to short path.
f7-Select Long Path.
This option toggles long path calculations.
f8-Change Parameters.
This returns you to the 7 choice initial menu to
change the various default parameters such as sunspot
number, antenna heights, power, etc.
f9-Quit.
Exits the program and returns you to DOS.
The program is entirely menu-driven so you don't have to remember
any special commands to use it.
Good luck!!
Some Technical Information:
The propagation is based upon the MINIMUF method, but with some
modifications of the author.
1-Rather than use the standard MINIMUF method of only looking at
the first and last ionospheric bounce points ( the two control
point method ), I calculate the propagation at every hop and
select the worst-case condition out of all of them. This results
in generally much more pessimistic MUF and LUF estimates than
MINIMUF.
2- I have included the E-layer screening frequency and lowest-
usable frequency ( LUF ) estimation technique given in chapter 4
of 'Amateur Radio Software ', by John Morris GM4ANB , RSGB
Books, Lambda House, Cranborne Road, Potters Bar, Hertfordshire
EN6 3JW. The subroutine starting at line 45000 contains this
calculation.
3-I have used what apparently is the HAM convention for longitudes
being positive-West for the input and output in this program, in
the MIMIMUF subroutine, and in the DX Atlas file MAPPER.ATL.
However, in the internals of the program I immediately reverse
the sign of the longitude. Being an engineer by training I think
in terms of right-handed coordinate systems! Therefore those who
want to modify the program should be wary of the sign of the
longitude being used.
4-Note that I have changed the names of the variables in the
MINIMUF subroutine from the standard values to names which are
descriptive of what the variable actually is.
5-I have augmented the propagation predictions with a signal
strength prediction. For each ionospheric control (bounce) point
an estimate of the D-layer absorption is made according to the
method in chapter 5 of Davies, "Ionospheric Radio Propagation",
NBS monograph 80, 1965. The total D-region absorption is summed
up for all control points. The subroutine at line 46000 contains
this calculation.
6-In addition, a calculation of the loss due to ground reflection
is made for each ground reflection point along the path. At each
of these points the map on the screen is checked to see if that
point is colored blue. If so, it is assumed that the bounce
point is at sea, and the reflection coefficient for sea water is
calculated ( dielectric constant of 80, conductivity of 4 mho/m
). If the reflection point is over land then a dielectric
constant of 4 and conductivity of 0.01 mho/m are used. The
Fresnel reflection coefficients for both horizontal an vertical
polarization are power-averaged to account for the random
polarization of the wave due to Faraday rotation at HF
frequencies. I have also modified the reflection coefficients to
account for surface roughness. A RMS surface roughness of 4m is
used on the sea, and 15m for land points. The subroutine at line
35000 makes the reflection calculations.
7-To account for the fact that most Hams have fairly low antenna
heights, thus suffer large losses at low elevation angles, I
explicitly calculate the multipath cancellation losses for each
antenna in the subroutine at line 36000. This is the standard
Fresnel reflection calculation without surface roughness
included. Most urban locations will be worse than this
calculation suggests because buildings in the foreground will
actually shadow the low angle line-of-sight and modify the
reflection area. If you know you have poor line-of-sight you
should modify the minimum launch angle setting at the initial
menu appropriately.
