DX Cluster — OpenHamClock Manual

What Is a DX Cluster?

A DX cluster is a network of servers that amateur radio operators use to announce interesting stations they have just heard or worked. When you hear a rare station, you post a spot: your callsign (the spotter), the DX callsign, frequency, and mode. That spot propagates instantly to thousands of operators worldwide.

OpenHamClock connects to the global DX Spider cluster network and displays the live spot feed, refreshed every 5 seconds. Each spot shows the DX callsign, frequency, band, mode, spotter, and how long ago it was posted. The most recent spots appear at the top.

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You do not need to log in to read spots

The DX cluster feed is read-only in OpenHamClock — you can see every spot without a callsign or account. Posting your own spots requires a direct telnet connection to a cluster node, which is outside the scope of this dashboard.

Reading the DX Cluster Panel

📶 Screenshot: DX Cluster panel with annotated callouts assets/img/screenshots/dx-cluster-panel.png

The DX Cluster panel. Each row is one spot: band colour strip on the left, DX callsign, frequency, mode, spotter callsign, and age. The toolbar at the top controls filters.

1 Band colour strip — matches the colour of the marker on the world map for that band.
2 DX callsign — the station being spotted. Click to draw the great-circle path on the map and open the DX Location panel.
3 Frequency — in kHz. Click to tune your rig (if Rig Bridge is configured).
4 Mode — CW, SSB, FT8, RTTY, etc. May be blank if the spotter did not include it.
5 Spotter — the operator who posted the spot, with their continent shown as a small flag.
6 Age — how long ago the spot was posted. Spots older than your retention window (default 30 min) are automatically removed.

Band Colour Coding

Every spot is colour-coded by band, making it immediately obvious which bands are active without reading the frequency numbers. The same palette is used on the world map markers, the Band Conditions panel, and the propagation indicators.

Colour	Band	Frequency range
Deep red	160 m	1.8 – 2.0 MHz
Orange	80 m	3.5 – 4.0 MHz
Yellow	40 m	7.0 – 7.3 MHz
Green	30 m	10.1 – 10.15 MHz
Blue	20 m	14.0 – 14.35 MHz
Dark blue	17 m	18.068 – 18.168 MHz
Indigo	15 m	21.0 – 21.45 MHz
Purple	12 m	24.89 – 24.99 MHz
Magenta	10 m	28.0 – 29.7 MHz
Teal	6 m	50 – 54 MHz
Grey	2 m and above	144 MHz+

Filtering Spots

The DX Cluster panel can quickly fill with hundreds of spots. The filter toolbar lets you narrow the view to exactly what interests you. Filters are per-browser and persist between sessions.

Band filter

Click any band button in the toolbar to show only spots on that band. Click again to deselect. Multiple bands can be active at once. Clicking ALL resets to the full feed.

Mode filter

Filter by operating mode: CW, SSB, FT8, RTTY, Digital, or All.

CQ Zone filter

Show only spots from a specific CQ zone, or spots to a specific zone. Useful for contest operators working a specific multiplier zone.

DXCC filter

Filter to show only spots from DX entities on your needs list. Enter the DXCC entity prefixes or names in the needs list in Settings → DX Cluster, and enable the needs-list filter in the toolbar to instantly highlight what you still need.

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Contesting tip: narrow before you start

Before a contest, set the band filter to the bands you plan to run, and the mode filter to CW or SSB. This dramatically reduces noise in the panel and lets you focus on mults appearing on your active bands only.

Watchlist & Audio Alerts

The watchlist is a personal list of callsigns (or callsign prefixes) that you are actively chasing. When any spot matching an entry appears in the feed, OpenHamClock highlights that row in the panel and can play an audio tone.

Adding callsigns to your watchlist

Open Settings → DX Cluster → Watchlist and enter callsigns one per line. You can use partial prefixes:

Watchlist entries (examples)

3B8            # any Mauritius station
VK9X           # Christmas Island prefix
ZL9            # Campbell Island
VP2E           # Anguilla
OA4TT          # specific callsign

Audio alerts

Enable Settings → DX Cluster → Audio alert on watchlist match. A short tone plays each time a watchlist callsign appears in a new spot. The tone volume is adjustable, and you can choose between a soft chime or a more attention-grabbing beep — useful if you are operating at the radio while the dashboard runs on a second screen.

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DXpedition chasing

When a major DXpedition is on the air (e.g. a rare Pacific island), add their callsign(s) to your watchlist before they activate. The moment their first spot hits the cluster you will hear the alert, no matter what else you are doing at the keyboard.

Spot Retention

By default spots are kept in the panel for 30 minutes before being removed. You can change this in .env:

.env

SPOT_RETENTION_MINUTES=30   # 5–120 is a practical range

A shorter window (10–15 min) keeps the panel focused on the freshest activity. A longer window (60 min) is useful for reviewing what was active over the past hour — helpful during a contest when you return to the radio after a break.

Data Sources

OpenHamClock can pull spots from several sources, configured via DX_CLUSTER_SOURCE in .env. See Configuration → DX Cluster Source for the full options. By default, auto mode tries sources in priority order and falls back gracefully if one is unavailable.

The DX Spider proxy is the most real-time source — it maintains a persistent telnet connection to a DX Spider cluster node and bridges it to the OpenHamClock API. This is what you want for serious DXing or contesting.