This is the full guide behind the Beacon Monitor tool on this site. Open the tool for the live cycle; read on for how the network works and how to get a real answer out of it in three minutes.
Every propagation prediction on the internet is a model. The NCDXF beacons are a measurement. Eighteen transmitters, spread from Nunavut to New Zealand, send the same thing at the same power on the same schedule whether anybody is listening or not, so what you copy from your own aerial is evidence rather than a forecast. Learn to use them and you can answer the question “is 15 metres open to Japan right now” in under three minutes, without asking anybody.
What is the NCDXF/IARU International Beacon Project?
The International Beacon Project (IBP) is a network of 18 amateur radio beacons operated by the Northern California DX Foundation together with the International Amateur Radio Union. The beacons transmit one after another on five HF bands, so a listener can judge propagation on a given path within a three minute window rather than guessing. Because the sequence is fixed and tied to UTC, the beacon on air at any instant can be calculated exactly, which is what the monitor above does.
The network exists because propagation is path dependent and nothing else on the bands is a controlled experiment. Two stations calling CQ tell you nothing comparable: one may be running a kilowatt into a stack of Yagis and the other a hundred watts into a wire. The beacons all run the same schedule and the same power steps from known locations, so the difference between what you hear from one and what you hear from another is the difference between the paths.
How the three minute beacon cycle works
Each beacon transmits for 10 seconds on one band, then moves to the next band while the following beacon takes over the frequency it just left. With 18 beacons and 10 second slots, one full cycle takes 180 seconds, or exactly three minutes. Every transmission is the beacon callsign sent in CW at 22 words per minute, followed by four one second dashes. The callsign and the first dash are sent at 100 watts, the remaining three dashes step down to 10 watts, 1 watt and 0.1 watt, so the number of dashes you can still copy tells you how strong the path really is.
The consequence worth internalising is that every one of the 18 beacons visits every one of the five bands once in every three minute cycle. Sit on one frequency for three minutes and you have sampled the whole world on that band. Sit there for two cycles and you have a repeat measurement, which is how you tell a genuine opening from a lucky burst.
NCDXF beacon frequencies
| Band | Frequency |
|---|---|
| 20 m | 14.100 MHz |
| 17 m | 18.110 MHz |
| 15 m | 21.150 MHz |
| 12 m | 24.930 MHz |
| 10 m | 28.200 MHz |
What the four dashes actually measure
The power steps are the cleverest part of the whole design. Each step down is a factor of ten, which is 10 dB, so the four dashes span 30 dB from first to last. Counting the dashes you can copy turns your receiver into a rough field strength meter without any equipment at all.
| What you copy | Power at the beacon | What it means for that path |
|---|---|---|
| Nothing | – | Closed, or below your noise floor |
| Callsign only, no dashes | 100 W | Marginal. CW and FT8 might work, SSB will not |
| Two dashes | Down to 10 W | A workable path for a normal station |
| Three dashes | Down to 1 W | Good. SSB with 100 watts should get through |
| Four dashes | Down to 0.1 W | Wide open. QRP conditions in that direction |
This is why a beacon check beats a cluster check for judging a path. A spot tells you that somebody somewhere heard a station. Copying the 0.1 watt dash from Pretoria tells you that you, with your antenna, at this minute, have 30 dB of margin on that path.
The 18 IBP beacons in transmission order
The beacons always transmit in the order below. Slot 1 starts each three minute cycle on 14.100 MHz at 00, 03, 06 minutes past the hour and so on.
| Slot | Callsign | Location | Grid |
|---|---|---|---|
| 1 | 4U1UN | United Nations, New York | FN30AS |
| 2 | VE8AT | Eureka, Nunavut, Canada | EQ79AX |
| 3 | W6WX | Mt Umunhum, California | CM97BD |
| 4 | KH6RS | Laie, Oahu, Hawaii | BL10TS |
| 5 | ZL6B | Masterton, New Zealand | RE78TW |
| 6 | VK6RBP | Rolystone, Perth, Australia | OF87AV |
| 7 | JA2IGY | Mt Asama, Japan | PM84JK |
| 8 | RR9O | Novosibirsk, Russia | NO14KX |
| 9 | VR2B | Hong Kong | OL72BG |
| 10 | 4S7B | Colombo, Sri Lanka | MJ96WV |
| 11 | ZS6DN | Pretoria, South Africa | KG44DC |
| 12 | 5Z4B | Kikuyu, Kenya | KI88HR |
| 13 | 4X6TU | Tel Aviv, Israel | KM72JB |
| 14 | OH2B | Lohja, Finland | KP20EH |
| 15 | CS3B | Santo da Serra, Madeira | IM12OR |
| 16 | LU4AA | Buenos Aires, Argentina | GF05TJ |
| 17 | OA4B | Lima, Peru | FH17MW |
| 18 | YV5B | Caracas, Venezuela | FK60NK |
How to find the beam heading to a beacon
Enter your Maidenhead locator in the box at the top of this page and the monitor calculates the great circle bearing and distance from your station to every beacon. Point a directional antenna at that bearing to give yourself the best chance of hearing the beacon, and remember that the reciprocal path works the same way: if you can hear a beacon well, stations in that direction stand a good chance of hearing you.
Treat that reciprocity as a rule of thumb rather than a law. The beacons run 100 watts into an omnidirectional antenna, which is a fair match for an average station, but your own receiving conditions and your local noise floor are not symmetrical with your transmitted signal. Hearing four dashes means the path is open. It does not guarantee that your hundred watts will land in the middle of a pile-up at the far end.
Three things to use the beacons for
Checking whether a path is open
This is the obvious one, and the monitor is built for it. Pick the band, sit on the frequency for a full cycle, and follow the highlighted row so you know which beacon you are hearing before the callsign arrives. Tick the ones you copy: the heard log stays in your browser and builds a picture of your real coverage over a few sessions.
Comparing two antennas honestly
Switch between antennas on consecutive cycles rather than mid-transmission, and count dashes from the same beacon each time. Three minutes apart is close enough that the ionosphere has not changed much, and the fixed power steps give you a number rather than an impression. Two dashes on one antenna and four on the other is a real 20 dB difference, which no amount of listening to somebody calling CQ would have told you.
Testing your own receiver and noise floor
Because the transmitted power is known, a beacon you used to copy at 1 watt and now only copy at 100 watts is telling you something has changed at your end. A new switched-mode power supply in the house, a failing coaxial connector or a noisy neighbour will show up on the beacons long before you notice it on the bands.
What the monitor cannot tell you
The page computes the schedule from the clock. It is not listening to the bands, and it has no way of knowing whether a given beacon is actually radiating. Beacons go off air for maintenance, for local licensing reasons and occasionally for years at a time, and the display will show them regardless. Silence where the table says there should be a signal means either the path is closed or that particular beacon is down, and only listening across a few cycles will tell you which.
One practical consequence: the display is only as accurate as your computer clock. If yours has drifted by ten seconds, so has the highlighted row. If the callsigns you copy are consistently one slot away from the one shown, check the clock on your machine before blaming the network.
For the wider picture, pair a beacon check with the propagation score, which models conditions from solar and geomagnetic data, and with the live DX cluster, which shows what people are actually working. The beacons measure your path, the score predicts the day, and the cluster reports the crowd. Disagreement between the three is usually the interesting part.
Frequently asked questions
Which beacon is transmitting right now?
The monitor at the top of this page shows the beacon on air on each of the five bands at this second, calculated from UTC. The schedule repeats every three minutes, so the same beacon returns to the same band at the same point in the next cycle.
What frequencies do the NCDXF beacons use?
14.100, 18.110, 21.150, 24.930 and 28.200 MHz. Listen in CW mode with a narrow filter, and remember that the beacon frequency is the carrier frequency, so set your dial exactly rather than tuning by ear.
How long does each beacon transmit?
Ten seconds on each band, then it hands the frequency to the next beacon in the sequence and moves up a band itself. Eighteen beacons at ten seconds each makes the three minute cycle.
What power do the IBP beacons run?
The callsign and the first dash go out at 100 watts, then the remaining three dashes step down to 10 watts, 1 watt and 0.1 watt. Each step is 10 dB, so the sequence spans 30 dB in total.
Do I need a beam antenna to hear the beacons?
No. A dipole or a vertical will copy the stronger beacons when a band is properly open. A beam raises the signal by several decibels and cuts noise from other directions, which is the difference between hearing one dash and three, but it is not a requirement for using the network.
What should I do if I hear nothing at all?
Give the frequency a full three minute cycle before concluding anything, because you may have arrived during a slot for a beacon on the far side of the world. If a whole cycle is silent, drop a band. A dead 10 metres and a busy 20 metres is the normal state of affairs for much of the solar cycle.
Are all 18 beacons always on the air?
No. Individual beacons go off air for maintenance, equipment failure or local licensing problems, sometimes for long periods. The NCDXF publishes the current status of the network, and it is worth checking there before deciding that a silent slot means a closed band.
Why can I hear a beacon but not work anyone in that country?
Because hearing is only half the path. The beacon is a known signal arriving at your receiver, but your transmitted signal has to reach the far end and compete with everybody else already there. A single dash from a rare entity means the path exists and is marginal, which usually calls for CW or a digital mode rather than SSB.