DX Cluster Preferences

SkookumLogger supports AR Cluster version 6.1 nodes in order to take advantage of the CT1BOH algorithm for assessing skimmer spot quality. Other types of nodes may or may not work as described here.

Logging in

To log in to a AR Cluster node, choose a node name in the  DX Cluster Node  popup list, enter a call in the  Login Call  text field, then click  Log In . You can use any call you want as the login call, but be aware that spot filters that you set up on the node are associated with that call. SkookumLogger remembers the log in status across sleep/wake and quit/restart cycles and automatically logs in when necessary. SkookumLogger also monitors traffic to detect outages.

Spot filters

You can define a spot filter on each AR-Cluster node. The definition is associated with your  Login Call  and remembered by the node (separately for each node) across logins. SkookumLogger provides a default spot filter, which will appear in your DX Cluster preferences Spot Filter box unless you have previously edited your filter.

AR-Cluster nodes have a powerful filtering capability that you can use to limit the number of spots that the node sends to you. The  Spot Filter  text box helps you construct an AR-Cluster filter. The default filter is:

((Call=[<buddies>]) OR ((BAND=[160,80,40,20,15,10,6,2]) AND (NOT Comment=[*PSK*,*TTY*,*BEACON*])))

The effects of this filter are to always receive DX announcements for calls in your buddies list, and otherwise receive only announcements for contest bands while rejecting spots that contain PSK, TYY, or BEACON in the spot comments field.

The spot filter understands a second token — <rejects>. Add this to your filter definition to cause calls in your <rejects> list to be filtered out by the node. For example:

((Call=[<buddies>]) OR ((NOT Call=[<rejects>]) AND (BAND=[160,80,40,20,15,10,6]) AND (NOT Comment=[*PSK*,*TTY*,*BEACON*,*JT*])))

In the examples, the asterisk is a “wildcard” that matches zero or more characters excluding whitespace characters. As a more complex example: 

(Call=[<buddies>] OR (SkimValid AND (BAND=[160,6] OR (BAND=[80,40,20,15,10] AND SpotterCqZone=5))))

 The effects of this filter are:

CT1BOH skimmer spot quality

Note: This information is borrowed from the documentation for the DXLog.net contest logging app.

To add spot quality flags to the comment field for skimmer spots, send this command to your AR Cluster node (using the DX Cluster window) after you  log in:

set dx extension skimmerquality

The setting is remembered when you log in again with the same call so you only need to do this once.

The CT1BOH skimmer quality algorithm is based on three parts:


When a callsign is first spotted, it is tagged with "?" in the last column of the spot's comment field. If the callsign of an unverified spot closely resembles an already verified one on the same frequency, the verified callsign is provided within parenthesis in the spot's comment field. When two or more skimmers agree on the spot, it is considered verified and the tag becomes "V".


When a verified spot appears more than 0.35kHz off its verified frequency, the spot is tagged "Q" for QSY. Once verified, this becomes the new verified frequency and it is tagged "V".


The algorithm checks uncertain spots for resemblance with already verified spots and spots at or near the same frequency. If the resemblance is high enough, the spot is considered busted "B" and the corrected callsign is provided within parenthesis in the spot's comment field.

If an unverified or busted spot includes a call in the comment field, SkookumLogger replaces the spotted call with that call and changes the flag to c or C, respectively, to indicate that the spotted call has been replaced by a corrected call.

Use these flags to judge the quality of an activity. You can also use flags named SKIMVALID, SKIMQSY, SKIMBUSTED and SKIMUNKNOWN, corresponding to V, Q, B, and ?, respectively, in your spot filter to pass or reject spots based on these flags. If you suppress delivery of unverified or busted spots, you will lose the ability for SkookumLogger to use the more likely call.

Other preferences

Ignore band-edge DX announcements  discards activities for frequencies at a lower band edge. Some illiterate DX cluster users send band-edge spots with messages in the information field as a way to broadcast to everyone.

Update Spot Filter at log in  sends your spot filter to the node each time you log in, so that you don’t have to remember to do that yourself after changing your buddies list or your rejects list. This feature relies on the node sending a line beginning with “Welcome” when you log in; standard AR-Cluster nodes do that and other node types usually do not.

The  Get WWV Forecast  button asks the AR-Cluster node to send a table of recent WWV propagation forecast data. When received, SkookumLogger displays the most recent data at the lower left corner of a  Great Circle map  window.  Get WWV Forecast at log in  performs that function each time you open a connection to an AR-Cluster node.

DX Cluster announcements generated by skimmers have reliable mode information. Other announcements do not, so the radio buttons provide choices for guessing the mode of non-skimmer spots. The default choice guesses mode based on the spot’s frequency relative to the phone band edge. The other choices assume all non-skimmer spots are either CW or SSB mode, for CW and SSB contests respectively. These choices are useful in events like the CQ 160m SSB contest, where there is no well-defined phone band edge.

The  DX Cluster Node  popup list has a few pre-defined sites. You add or remove items by clicking  Edit List  to open the DX Cluster Nodes window with a table listing node names and URLs. The  Name  for a node can be anything you like.  Address  must be a valid URL, optionally followed by a colon and a port number. SkookumLogger assumes the port number is 23 (the telnet default) when none is supplied. Click the  DX Cluster Web Site  button to visit a web page containing a large table of DX Cluster nodes, included their addresses and their software versions.

SkookumLogger  3.13  © 2023 K1GQ