using

Using The Program

This program is intended to show the locations of the many amateur radio callsigns which can be heard on a Short Wave receiver. It also provides useful information for a radio amateur, such as his distance from the station heard, and the time at the remote station.

It can be used in two ways:
1: Enter a callsign you have heard to find where the station is located.
2: Click anywhere on the Earth to find the name of the Country, and the Callsign letter ranges allocated to that Country.

The main screen displays satellite images of the Earth, which can be 'rotated' to show all parts of the World, using the keyboard arrow keys.

When you first run the program, it asks for your Home Latitude and Longitude, which you can look up on a map. When you enter this information, it is stored in a file 'global.ini' in the folder from which you start the program. The screen displays the Home Location with a flashing green marker, and the Local Time (as set on your computer).

Installing the Program

Copy the file ‘global.zip’ to a suitable working folder, and unzip it. The files include the executable program ‘global.exe’. Set up a shortcut to the .exe file to use the program. The source code is the file ‘global.cba’, in which you may find some useful bits of code to use in your own programs. Other files are the images used by the program and the prefixes file 'prefix.txt'.

Amateur Callsigns

Each licensed amateur who operates a radio transmitter, is assigned a unique Callsign by the licensing agency in his Country. Throughout the World, no two amateur radio stations have the same callsign. Transmitting station identification by callsign is required by international law.

A callsign is an alpha-numeric code of between 4 and 6 characters. It will have at least one number in the group. The first one or two characters indicate in which Country the station is located. For example, a Swedish station would have a callsign beginning with the prefix ‘SM’.

Each Country has been allocated a unique series of Prefixes. Larger Countries will have several prefixes. For example, the United States has one-letter prefixes K, L, N and W, or two-letter prefixes in ranges AA – AL, KA – KZ, NA – NZ, and WA – WZ.

The number in a callsign can indicate a Region of the Country in which it was issued, but in some cases, one of the letters is used for this purpose. For example, the prefix ‘GM’ indicates a station in Scotland.

The last few characters of a callsign – the suffix – are not usually meaningful (except in Russia), and are assigned sequentially when an amateur is licensed.

Locating a Callsign

If you hear a callsign and wish to know which Country it is, you can enter it in the lower right box, and click ‘Show’. If it is a known callsign, the station will be indicated with a flashing red marker, and the Country name will appear at the top left. The ‘Great Circle’ distance between your Home location and the remote station is also shown, together with the time at the remote station.

Looking up Callsign Prefixes allocated to a Country

To find the prefixes allocated to a particular Country, click on the map. The Country details and prefixes will be listed, the distance from your Home location, and the remote station time. To clear the display, click 'Clear'.

The Country Prefix List

The information on which the program works is stored in a file ‘prefix.txt’. This file should be located in the same folder from which the program is launched.

In addition to Callsign prefixes, it holds details of about 2000 co-ordinates which represent Countries. When you click on the Earth, the nearest co-ordinate is used to establish the Country involved. The file of active locations, is editable using Notepad should you need to alter any values, or to add additional points..

A typical entry is:

Western Samoa 5W - -13.82 172.1

This gives the Country name, followed by its allocated prefix (or prefix range if any). The dash after the 5W indicates there is no range of characters in the above case. The last two numbers are the Latitude and Longitude of the approximate centre of the Country.

Many of the allocated prefix range values are unlikely to be heard since most Countries only use a limited number of prefixes from their allocation. If new prefixes are allocated in future, they can easily be added to the ‘prefix.txt’ database.

Latitudes are positive in the Northern Hemisphere, and negative in the Southern. They range from +90 degrees at the North Pole, through 0 degrees at the Equator, to –90 degrees at the South Pole.

Longitudes are negative West of Greenwich (0 degrees), and positive to the East. They range from 0 degrees at the Greenwich meridian, to –180 degrees in a Westerly direction, and to +180 degrees to the East.

NOTE:
In the 'prefix.txt' file, it is important that TAB characters are used to separate items on a given line of data. The program uses these to separate the data into its working arrays.

The Name field should use a Space separator if there are two words, as in the example above. The name field is then separated from the following prefix field by one or more Tabs, and similarly for the rest of the data on the line.

You will not need to edit the prefix file very often. If you do try it, be sure to keep a backup copy in case of problems. There are currently over 2000 entries, and the program is set for a maximum of 2300. If you need more, you will need to increase the value of ‘nlmax’ near the start of the program.

The above example is typical of most of the entries in the file, although many Countries will have a range of prefixes. For example, the dash after the 5W in the example above, might have been 5Z instead, indicating that callsigns might then occur for Western Samoa using prefixes anywhere in the range 5W to 5Z.

Another typical entry (if you examine the file), will have both prefix fields as dashes. What’s the point of that you might wonder? Some Countries cover a large geographic area. When you click on the map, you may not click on an ‘active’ point. Therefore, it is sometimes necessary to have ‘extra’ active points scattered around a large Country, representing several co-ordinates within the Country. This minimises the chance of you clicking on a 'dead spot'. These do not need to specify the Prefix range again, so two dashes are inserted instead.

The program is set to a click ‘sensitivity’ of 2 degrees of Latitude / Longitude (this can be altered by changing program variable ‘msens’) about a given active data point. If you click near enough to an active point, the Country details will appear.

In other cases, as for example, the United States, Russia, and China, regions have been allocated specific characters in the callsigns. These regions are usually very broad. For example, the United States is divided into only 10 regions. Region 4 for example, covering the whole of the South Eastern area of the US. If you enter a callsign such as WB4IJK, and ‘Show’ it on the map, the name displayed can only locate the station within the South Eastern USA region.

However, if you click on the map, you will probably get a more specific location, such as Virginia. The prefix ranges in use will of course be the same throughout an allocated region.

So how is this done? Near the end of the prefix file you will find a list of much more specific location names, followed by a prefix such as W4~ . This is simply a surrogate prefix for the broader region, to allow the local co-ordinates, and name, to be specified. The program relates these to the broader region prefixes W0, W1, W2, etc. when determining the available prefix ranges.

A similar set of surrogates is used for the China (B series).

If you leave a blank line in the Prefix file, the program will stop reading the file when it reaches the blank line. Only the data above the blank line will be processed.

Finally

This program has been written in Creative Basic.

There are a lot of subroutines in the program. Some testing has been done, but there may still be bugs and coding problems which I haven't dealt with. If you find a problem, let me know - or better still, get your own copy of Creative Basic and fix it yourself ..

Enjoy,

Graham (G4EVW)

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