Shareware Grab Bag

home *** CD-ROM | disk | FTP | other *** search

/ Shareware Grab Bag / Shareware Grab Bag.iso / 090 / mapper3a.arc / MAPPER3.DOC < prev

Wrap

Text File | 1988-01-22 | 14.3 KB | 291 lines

MAPPER3 .. A DX MAP DRAWING and Propagation Program for IBM PC Compatibles with graphics capability. Version 3.0 by Dennis P. Murray 11165 McDonald Street Culver City, Ca. 90230 CompuServ 72770,2765 22 January, 1988 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- MAPPER3.BAS The Program Source Code 2- MAPPER3.EXE the Q-BASIC v4.0 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. 6- MAPPER3.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 'MAPPER3'. 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.