NCDXF Beacons: Checking HF Propagation in Three Minutes

Every HF operator eventually asks the same question before calling CQ: is the band actually open, and to where? Propagation forecasts give you a probability, cluster spots tell you what someone else heard, but the NCDXF beacons let you hear the answer yourself. Eighteen stations around the world take turns transmitting on five fixed frequencies, around the clock, in a precise schedule. With a receiver, an accurate clock and a few minutes of listening, you can build a live picture of which paths are open from your own antenna.

This guide explains how the International Beacon Project works, where and when the beacons transmit, how to identify what you hear, how to interpret the power steps, and which tools make monitoring easier. It also covers the limits of the system, so you know what a silent frequency does and does not mean.

What the International Beacon Project Is

The International Beacon Project (IBP) is a worldwide network of CW propagation beacons coordinated by the Northern California DX Foundation (NCDXF) and the International Amateur Radio Union (IARU). The first beacon went on the air from Northern California in 1979. Over the years the network grew to its current layout of eighteen transmitting sites spread across every continent, each operated by a local amateur radio society or volunteer group.

The design goal is simple: give every listener a reliable, known signal source in a known direction at a known time. Because the schedule never changes, you do not need to guess who is transmitting. If you hear a signal on a beacon frequency at a given second, the schedule tells you exactly which site it came from and, therefore, which path is open.

The IARU explains on its beacons page that, apart from short-term experiments, it does not support amateur beacons below 14 MHz because those bands are too congested. That is why the network starts on 20 meters and stops on 10 meters.

Frequencies and the Three-Minute Schedule

The beacons share five frequencies, one in each of the HF bands from 20 to 10 meters:

• 14.100 MHz (20 m)
• 18.110 MHz (17 m)
• 21.150 MHz (15 m)
• 24.930 MHz (12 m)
• 28.200 MHz (10 m)

Each beacon transmits once on each band once every three minutes, 24 hours a day. A single transmission lasts ten seconds. When it ends, that beacon steps up to the next higher band, and the next beacon in the sequence starts on the frequency it just left. The result is a rolling pattern: at any moment five beacons are on the air, one per band, and over three minutes every beacon has appeared on every band.

Because 18 beacons times 10 seconds equals 180 seconds, the whole cycle repeats every three minutes, aligned to UTC. That alignment is the reason an accurate clock matters so much. If your PC or radio clock is off by several seconds, you will attribute a signal to the wrong beacon. Synchronise your computer clock with an internet time service before a monitoring session, exactly as you would for FT8.

The beacon sequence

The transmitting order, as published by NCDXF, is:

4U1UN (United Nations, New York), VE8AT (Canada, now located at Inuvik), W6WX (California), KH6RS (Hawaii), ZL6B (New Zealand), VK6RBP (Western Australia), JA2IGY (Japan), RR9O (Russia, Siberia), VR2B (Hong Kong), 4S7B (Sri Lanka), ZS6DN (South Africa), 5Z4B (Kenya), 4X6TU (Israel), OH2B (Finland), CS3B (Madeira), LU4AA (Argentina), OA4B (Peru) and YV5B (Venezuela).

The order roughly walks around the globe, which is helpful when you listen for a while: you hear North America, then the Pacific, Asia, Africa, Europe and South America in turn. Beacons occasionally go off the air for maintenance or power problems, so always check the status notes on the official NCDXF beacon schedule page before concluding that a path is closed.

What Each Transmission Sounds Like

Every ten-second slot follows the same format. The beacon sends its callsign in CW at 22 words per minute, followed by four dashes, each one second long. The callsign and the first dash are sent at 100 watts. The remaining three dashes are sent at 10 watts, 1 watt and 100 milliwatts.

Those power steps are the most useful part of the transmission. Each step is 10 dB lower than the previous one. If you can hear all four dashes, the path is strong enough that even a very low-power signal would get through. If the signal disappears after the first dash, the path is open but marginal at 100 watts. Counting dashes is a quick, practical way to estimate path strength in 10 dB steps without an S-meter calibration.

Reading the dashes

Think of the dashes as a rough link budget in your headphones:

• Callsign only, faint: the path exists, but a 100 W station would struggle. Expect weak signals and difficult QSOs.
• Callsign and first dash: workable with 100 W and a reasonable antenna, especially on CW and digital modes.
• Two or three dashes: a good opening. SSB contacts at modest power are realistic.
• All four dashes: an excellent path. QRP operators should be on the air right now.

Remember that the beacons use simple, broadly omnidirectional antennas rather than beams, and that local noise at your station affects what you hear. The comparison is most meaningful when you track the same beacon over days from the same antenna.

How to Listen: A Practical Routine

You do not need special equipment. Any HF receiver that covers the five frequencies will do. A useful routine looks like this:

1. Set your clock. Sync the computer or radio clock to UTC within a second or so.
2. Pick a band. Start with the band you plan to operate. Tune to its beacon frequency in CW mode with a normal CW filter.
3. Listen for a full three minutes. Note which callsigns you copy and how many dashes you hear for each.
4. Compare bands. Repeat on neighbouring bands. You will often find that 15 m is open to one region while 20 m favours another.
5. Act on it. Point your beam, choose the band, and look for activity from the regions you heard.

If you cannot copy CW at 22 words per minute yet, do not worry. Software can do it for you, and after a few sessions you will recognise the rhythm of the common callsigns by ear. Our guide to HF propagation explains why a band can be open to one continent and dead to another at the same moment.

Software That Monitors the Beacons for You

Several programs automate beacon monitoring. The best known is Faros, which listens through the sound card, synchronises to the schedule, detects each beacon and plots signal-to-noise and dash counts over time. Left running for a day, it produces a chart showing when each path opened and closed, which is a remarkable way to learn propagation patterns at your location.

Many logging and rig control programs also include a beacon display that simply shows which beacon should be transmitting on each band right now. Combined with CAT control, some can step your radio through the five frequencies automatically. The NCDXF site lists tools for Windows, macOS, Linux, Android and iOS, as well as web-based schedules you can keep open in a browser tab.

Beacon spots also appear in automated networks. The Reverse Beacon Network and similar skimmer-based systems decode CW signals, including the IBP beacons, and publish what they hear. That lets you check whether a beacon is being heard in a given region even when you are away from the radio. Our article on CW Skimmer and the Reverse Beacon Network explains how those spots are generated.

Beacons Compared With Other Propagation Tools

The IBP is one tool among several. Each answers a slightly different question, and experienced operators combine them.

Beacons are the only tool on this list that measures propagation from a known transmitter to your own receive antenna. That makes them particularly good at answering a very local question: can I hear that region, here, now? If you want to see how your own signal gets out, PSK Reporter and skimmer networks answer the reverse question.

Interpreting What You Hear

A few patterns show up again and again once you start listening regularly.

Gray line and daylight paths

The higher bands, 15, 12 and 10 meters, generally need a sunlit path. You will often hear beacons in regions that are in daylight at the same time as you, and hear them fade as the sun sets on either end. Around sunrise and sunset, gray line paths can bring surprisingly strong signals from beacons that were silent an hour earlier.

Solar activity

When solar activity is high, 10 and 12 meters can carry beacons from several continents at once. In quieter years the upper bands may be silent for days, and 20 meters becomes the main band where you hear the network. Geomagnetic disturbances tend to weaken polar paths first, so beacons whose signals cross high latitudes are good early indicators of a disturbance. Our explainer on solar flux, A-index and K-index connects those numbers with what you hear.

One-way openings

Propagation is usually reciprocal, but noise is not. You may hear a beacon clearly while a station in that region cannot hear you, simply because their local noise is higher or their antenna is poorer. Treat a strong beacon as a sign the path exists, not a guarantee that every contact will work.

Using the Beacons in Contests and DX Chasing

Contesters use the beacons to decide band changes. Before moving a run to a higher band, a quick listen on the beacon frequency tells you whether the target region is already coming through. Multi-operator stations sometimes leave a receiver parked on a beacon frequency with monitoring software, so the team can see openings develop on a chart.

DX chasers use them differently. If a rare station is expected on 12 meters from a region served by one of the beacons, checking that beacon over several days shows when the path typically opens at your location. That turns a forecast into a personal schedule: you know the hour when your chances are best.

Always keep the beacon frequencies clear. Do not call CQ, tune up or park a digital signal on or near them. Many band plans mark them as beacon segments, and interference ruins the measurements for thousands of listeners. Band plan details differ between IARU regions, so check the plan for your region, but the beacon frequencies themselves are the same worldwide.

Limits and Common Mistakes

The system is simple, but a few mistakes are common:

• Wrong clock. A few seconds of error shifts every identification by one slot. Always sync first.
• Assuming silence means closed. A beacon may be off the air. Check the status notes before drawing conclusions.
• Ignoring your noise floor. Local noise can hide the weaker dashes. If you have a noise problem, the beacons are a good way to measure the improvement after you fix it.
• Reading one sample as a trend. Propagation changes minute by minute. One cycle is a snapshot; several cycles are a picture.
• Forgetting antenna direction. With a beam, a beacon off the back may vanish. Point the antenna, or use an omnidirectional antenna for general monitoring.

The Bottom Line

The NCDXF beacons turn propagation from a forecast into something you can hear. Eighteen stations, five frequencies, ten-second slots and four power steps give you a complete survey of HF paths from your own antenna every three minutes. Sync your clock, listen through a full cycle, count the dashes and compare bands, or let software log the whole day for you. Combined with skimmer data, PSK Reporter and cluster spots, the beacons give you a clear, local answer to the question every operator asks: where is the band open right now?

Frequently Asked Questions

What frequencies do the NCDXF beacons use?

They use 14.100, 18.110, 21.150, 24.930 and 28.200 MHz. There are no IBP beacons below 20 meters because the IARU does not support beacons on the more congested lower bands.

How often does each beacon transmit?

Each beacon transmits for ten seconds on each band once every three minutes, around the clock. After each slot it moves to the next higher band and the next beacon takes its place.

What do the four dashes after the callsign mean?

They are power steps. The first dash is sent at 100 watts, then 10 watts, 1 watt and 100 milliwatts. The number of dashes you hear gives a rough measure of path strength in 10 dB steps.

Why do I hear the wrong beacon at the wrong time?

Almost always because your clock is off. The schedule is locked to UTC, so sync your computer or radio clock before identifying signals by time.

Do I need to read CW to use the beacons?

No. Software such as Faros or a schedule display can identify each beacon for you. With practice you will also learn to recognise common callsigns by ear.

Can I transmit near the beacon frequencies?

You should keep them clear. Transmitting on or next to a beacon frequency spoils the measurement for listeners worldwide, and band plans mark these frequencies for beacon use.