Command Line

c:\Program Files\DX Monitor\DXmon AUTO

Starting DX Monitor with a command line argument of AUTO forces the program to go into AUTO mode regardless of how it was shut down. Normally it retains the AUTO mode if it was on when shut down.

Running Multiple Copies of DX Monitor

Prior to version 0.99 it was possible to run two or more copies of DX Monitor simultaneously as long as they were in separate folders. After version 0.99, it is not possible to run two copies at once.

If there is demand for running multiple copies, please let me know and I will make the necessary changes.

Files Associated with DX Monitor

Almost all the files associated with the program are plain text files which can be read with a good text editor or used by other programs to extract data for other purposes. In most cases, the format is fixed column width and easily determined by examining the file.


In order to determine the location of DX spots, DX Monitor uses the CTY.DAT file created by K1EA Software for the excellent CT contest logging program. This file is updated regularly by Jim Reisert, AD1C, to include new countries and special prefixes. The latest version can be obtained from Once a day, DX Monitor checks the date of the latest CTY.DAT file and compares it with the one you are using. If your file appears to be older than the latest version, the program will download the new one and replace the old one. The old file will be saved in a form such as CTY.DAT.2006-04-03733.bak, and you will be alerted to the change. You can revert to the old file by copying the backup over cty.dat in Windows Explorer.

Note that the location of cty.dat moved on August 19 2006 and earlier versions of DX Monitor will point to the old location.

Note that in 2020 the secure URL is required. Please change the URL in the Preferences/URLs/URL for CTY.DAT to ensure that you are getting the current data.

If you wish to add a new prefix to a country in CTY.DAT while awaiting the official update, the file can be edited (carefully) with the freeware text editor Editpad Lite. For example, to add TX9 as a prefix for Chesterfield Island, change:

Chesterfield Is.:         30:  56:  OC:  -19.90:  -158.30:   -11.0:  FK/C:
Chesterfield Is.:         30:  56:  OC:  -19.90:  -158.30:   -11.0:  FK/C:

REGIONS.DAT CTY.DAT does not show locations more accurately than by country. In the case of larger countries that have geographically accurate prefixes (VE, VK, PY, UA) there is a subfile, REGIONS.DAT, which is used to locate stations from those countries. Special prefixes are translated to the "normalized" prefix for the country, which is used to look up the location. If a new callsign is being wrongly identified by the program, it is easy to add a line to the REGIONS.DAT file containing the correct latitude, longitude and country description.

I would appreciate help from users who add to this data file. Please send me your additions or changes. The file is in fixed column format.


This is a list of callsigns and locations which overrides the default location specified by prefix. It contains a few special stations, such as the NCDXF Beacons, and approximately 2,000 of the most popular calls on DX Monitor from the US and Canada.

Additional calls can be added manually to the list. Additions should follow the format of the list, in fixed spacing.


This DLL is used to access the Callbook CDrom. Even if you don't have the CD, it must be available for DX Monitor at startup. It can be placed in the same folder with the dxmon.exe executable, or it can be moved to your WINDOWS or WINDOWS\SYSTEM directory. If you have already installed this file for another program, it is best to use only one of them at a time.


This tab delimited file is used to describe the timing and frequencies of active beacons. If the beacons change, the file can be modified. It is in tab-delimited format suitable for editing with any spreadsheet program or a text editor which does not modify the format.


This plain text file contains a list of time servers which can be used to retrieve the current correct time.


This plain text file contains a list stations that upload their logs to the ARRL Logbook of the World. It is downloaded from HB9BZA’s web site with the Update LOTW command.


This is an image file containing the Mercator projection world map. The Azimuthal projection map is created from this map. If you wish to change the colors or improve the map, just make sure the locations don't move. Please share any improvements with all of us by sending me a copy.

Files created by DX Monitor

...\data folder contains the data files created by DX Monitor.
DXDB.txt contains the recent 1000 to 2000 spots.
DXHistory.txt contains the older spots up to the limit set in User Preferences.
WWVHistory.txt contains the WWV History.
AnnHistory.txt contains the announcement history.

dxmon.ini contains the settings for DX Monitor.
TIME.LOG contains the log of adjustments made to the system clock in RTF format.
DXALARMS.TXT contains the DX alerts you have created.
SKEDS.TXT contains the time alarms that you have created.
TNServers.txt contains the list of Telnet servers.
DXMTelnet.ini contains the settings for the Telnet Application.

...\maps folder contains maps created by DX Monitor.
AZ3122....PNG contains the azimuthal map for 37 degrees north, 122 degrees west. Yours will have a similar name with your latitude and longitude.
MR3122....PNG contains the Mercatore map for 37 degrees north, 122 degrees west.
VERSION.TXT contains the last version information downloaded daily.

...\tmp is a directory which is created while the program is running. It is deleted when the program exits normally. If the program crashes, the files in this directory may contain clues to the problem.

Autosave Grid on Updates can be used to save a copy of the displayed main grid for use by other programs. The file name and location are set by the last Save Grid As ....