DX cluster
| DX cluster | |
|---|---|
| What it is | A network for sharing reports, called spots, of stations heard on the air |
| Began | 1980s, on packet radio |
| Today | Internet-linked nodes reached by telnet, websites and apps |
| Node software | DX Spider, AR-Cluster, CC Cluster |
| Spots | |
| A spot gives | Spotter, frequency, station heard, comment, time in UTC |
| Spotting command | DX frequency call sign comment |
| Used through | Logging software, band maps, web clusters |
| Related network | Reverse Beacon Network |
A DX cluster is a network on which hams share spots, short reports that a particular station is on the air on a particular frequency. A spot posted by one operator reaches thousands of others within seconds, so when a rare station appears, DXers around the world know almost at once. Clusters began in the 1980s as linked packet radio stations; today they run over the internet, and most hams use them through their logging software or a website rather than by connecting directly.
How it works
A cluster is made up of nodes, computers run by volunteers or clubs, each linked to many others. A user connects to any one node, logs in with a call sign, and from then on sees every spot posted anywhere on the linked network, along with announcements and a few other services such as propagation data. When the user posts a spot, the node passes it on to the rest of the network.
The original software, PacketCluster, ran on packet radio nodes connected by radio links. Its modern successors include DX Spider, AR-Cluster and CC Cluster, which do the same job over the internet. Users usually connect with telnet, a simple text connection: any telnet program, or a logging program pointed at a node's address and port, will do. Commands differ a little from one node program to another, but the basics are much the same, for example SH/DX to show recent spots.
Web clusters such as DX Summit show the same stream of spots on a web page, with search and filtering, and need no software at all. Many are linked to the telnet network, so a spot posted on one appears on the others. Phone apps and alert services can send a notice when a wanted station is spotted.
Reading and posting spots
A spot on a telnet node looks like this:
DX de K1ABC: 14025.0 ZS6XYZ CW, listening up 2 1432Z
The line shows the spotter's call sign (K1ABC), the frequency in kilohertz (14,025.0 kHz), the station heard (ZS6XYZ), a short comment, and the time in UTC. Some nodes add the spotter's grid square or location. Comments often give the mode or say that the station is working split, transmitting on one frequency and listening on another.
To post a spot, type DX, the frequency in kilohertz, the call sign and an optional comment, for example DX 14025.0 ZS6XYZ CW up 2. Logging programs and web clusters offer a form or a button that does the same.
Spots from Reverse Beacon Network skimmers, marked with a "-#" after the skimmer's call sign, are carried on many nodes and can greatly outnumber human spots. Most nodes let users filter them.
Using spots
Most logging programs can connect to a cluster and show spots in a list or on a band map, a scale of each band with spotted stations marked at their frequencies. Clicking a spot tunes the radio there through its computer control connection, and the program can highlight stations whose country, state or zone is still needed for an award.
Filters are what make a cluster useful. Spots posted by stations far away describe their propagation, not yours, so it is common to show only spots posted from the same continent or region. Filtering by band and mode removes the rest of the clutter.
In contests, using spots usually puts an operator in an "assisted" or "unlimited" category, so check the contest rules before connecting.
Etiquette
- Don't spot yourself on a DX cluster, and don't ask others to spot you. It is frowned upon in general and forbidden by the rules of most contests. Programs such as Parks on the Air and Summits on the Air, which encourage activators to post their own spots on their own websites, are the common exception.
- Check the call sign and frequency before posting. A wrong spot sends hundreds of operators to the wrong place.
- Keep comments useful. Mode, split instructions and an Islands on the Air or park reference help; complaints, arguments and personal messages do not belong in spots.
- Don't spot a station that doesn't want the attention, such as a ragchew between friends, and don't use spots to complain about other operators.