Long Path DX: When to Turn Your Antenna the Other Way
Most HF contacts travel the obvious way: along the shortest route around the globe between two stations. But every pair of points on Earth is connected by two great circle routes, a short one and a long one going the opposite direction. Sometimes the short route is closed while the long one is wide open. Long path DX is the art of noticing those moments and pointing your antenna, quite literally, the wrong way.
For DXers with a rotatable beam, long path openings explain some of the most surprising contacts in the log: a Pacific station that is loud from the “wrong” direction, a signal with a hollow echo, or a band that seems dead towards a target until you turn the beam around. This guide explains the geometry, the propagation conditions that make long path work, how to recognise an opening, and practical ways to use it, whether you run a beam or a wire antenna.
Short Path and Long Path: The Geometry
A great circle is any circle on the surface of a sphere whose centre is the centre of the sphere. The shortest route between two points on Earth always lies along a great circle, which is why aircraft routes often look curved on flat maps. The great circle distance is the length of that short route.
The same great circle, followed in the opposite direction, is the long path. Together the two routes add up to the full circumference of the Earth, roughly 40,000 km. So if the short path to a station is 15,000 km, the long path is about 25,000 km. If the short path is 19,000 km, the station is close to your antipode, and the two paths are almost the same length.
Two practical rules follow:
- The long path bearing is the short path bearing plus 180 degrees. If the short path to a station is 60 degrees, the long path is 240 degrees.
- Long path only makes sense for distant stations. For a station 3,000 km away, the long path is around 37,000 km, and many extra hops make it impractical. Long path matters most for stations that are already far away on the short path.
An azimuthal equidistant map centred on your own location shows both paths clearly: the short path is the straight line from the centre to the target, and the long path leaves the centre in the opposite direction and wraps around the edge of the map. The azimuthal equidistant projection is the standard great circle map for exactly this reason.
Why a Longer Path Can Be Better
At first glance, a signal travelling 25,000 km should always lose to the same signal travelling 15,000 km. Usually it does. But HF propagation is not just about distance. What matters is whether every hop along the path finds an ionosphere able to refract the signal, and whether the signal avoids heavy absorption on the way.
The short path can fail in several ways:
- It crosses a region where the maximum usable frequency is too low, for example a long stretch of night-time ionosphere on a high band.
- It crosses a region of heavy daytime absorption, which especially hurts the lower bands.
- It passes close to the auroral zone, where geomagnetic activity can absorb or scatter signals badly.
The long path may avoid all three. A path that runs mostly through darkness can work well on the low bands, where night-time absorption is low. A path that runs mostly through daylight can work on the high bands, where the sunlit ionosphere supports higher frequencies. And a path that runs well away from the poles can stay open while the short path is disturbed by aurora. If you want the background, our article on what really decides whether you are heard on HF explains the role of the ionospheric layers and absorption.
Long Path and the Gray Line
Many classic long path openings happen near sunrise or sunset, along the boundary between day and night. This boundary is called the terminator or solar terminator, and radio amateurs usually call it the gray line.
Along the gray line, the lower ionospheric layers that cause daytime absorption have weakened or not yet formed, while the higher layers still refract signals well. When the long path between two stations runs roughly along the gray line, signals can travel a remarkable distance with relatively little loss. That is why low band DXers often watch sunrise and sunset times at both ends of a path, and why a long path opening on 40 or 80 metres can last only minutes.
Our article on sporadic-E and gray line propagation techniques covers the gray line in more depth. The key point for long path work is simple: if the short path is closed and one or both stations are near sunrise or sunset, check the long path.
Short Path vs Long Path at a Glance
The table below compares the two paths in general terms. Real conditions depend on band, season, time of day and the solar cycle, so treat it as a guide to what to check, not a forecast.
| Factor | Short path | Long path |
|---|---|---|
| Distance | Shortest great circle route | Remainder of the circumference, always longer |
| Antenna bearing | Direct bearing to the station | Direct bearing plus 180 degrees |
| Number of hops | Fewer | More, so each hop must be efficient |
| Typical favourable conditions | Whenever the path’s ionosphere supports the band | Path mostly in darkness (low bands) or daylight (high bands), or along the gray line |
| Duration of openings | Often hours | Often shorter, sometimes only minutes on the low bands |
| Auroral exposure | Depends on the path; polar routes suffer | Can avoid the polar regions when the short path crosses them |
| Signal character | Usually clean | May show echo or flutter, especially if both paths are open |
How to Recognise a Long Path Opening
Long path signals often reveal themselves before you even turn your antenna. Here are the signs experienced DXers look for.
The signal is louder off the back of the beam
With a directional antenna, the clearest test is to rotate it. If a distant station peaks at the short path bearing plus 180 degrees, you are hearing the long path. Sometimes the signal peaks somewhere between the two, which may indicate skew path propagation, where the signal is scattered or refracted away from the great circle.
An echo on the signal
When both paths are open at the same time, the same signal reaches you twice: once by the short path and again, a fraction of a second later, by the long path. On SSB this sounds like a hollow, reverberant voice; on CW the dits seem smeared. The echo is a strong hint that the long path is alive and that rotating the beam may improve the signal.
Spots and reports from unexpected directions
DX cluster spots and reception reports can show long path openings too. If stations in your area are working a distant region while the short path towards it should be closed, the long path is a likely explanation. Reverse beacon data and reception reports from digital modes are useful for the same reason. Our guide to DX clusters and spotting etiquette explains how to read spots without drowning in them.
Beacons
The international beacon network transmits from fixed locations on a known schedule, so it is a reliable way to test a path. If a distant beacon is audible and strongest off the back of your beam, the long path is open on that band.
Working Long Path With a Beam
A rotatable beam is the ideal long path tool, because you can compare both directions in seconds. A practical routine:
- Know both bearings. Keep a list of long path bearings to the regions you chase most, or use a logging program that shows both bearings for each callsign.
- Listen in both directions. When a wanted station is weak, swing the beam through 180 degrees and listen again. Do this before you start calling.
- Check intermediate headings. If neither the short nor long bearing is best, try angles in between to see whether skew path is at work.
- Tell the other station. On SSB or CW, a short note such as “long path here” helps the other operator turn their antenna too, which can make a big difference on a marginal path.
- Move quickly. Long path openings, especially on the low bands, can be brief. Have the rotator and the radio ready before the expected opening.
If your rotator is slow or inaccurate, long path work exposes it quickly. Our article on sizing and controlling an antenna rotator covers calibration and computer control, which make quick swings much easier.
Long Path With Wire Antennas and Verticals
You do not need a beam to work long path. A vertical radiates in all directions, so it will hear the long path whenever it is open; you simply cannot choose between the two paths. A dipole has a broad figure-of-eight pattern, and its two main lobes point in opposite directions. That means a dipole broadside to a distant region favours both the short path and the long path towards it, which is convenient.
With wire antennas, the main long path skills are timing and listening. Note when echoes appear, keep track of sunrise and sunset at both ends of the path, and learn when your favourite long path openings occur. Over a season, patterns emerge that tell you when to be at the radio.
Planning and Prediction
Propagation prediction tools can model both short and long path, and many of them let you choose which one to display. They are good at showing when a path is likely to be supported by the ionosphere, though they are less reliable for brief gray line openings. Our overview of VOACAP and propagation prediction tools explains how to use them for planning.
Space weather matters too. During geomagnetic disturbances, high-latitude short paths can close quickly, which is exactly when a long path that avoids the auroral zone may be the only way through. Current conditions and alerts are published by NOAA’s Space Weather Prediction Center.
Finally, keep notes. A simple log entry such as “long path, strong echo, 15 minutes after local sunrise” is worth more than any general rule, because it describes your antenna, your location and your typical target. Many DXers also set alerts for the stations they need, so that when a long path window opens and the station is spotted, they are already at the radio rather than finding out the next day.
Common Long Path Mistakes
- Never checking the back of the beam. Many operators simply never turn the beam away from the direct bearing and miss openings entirely.
- Assuming the long path is always weaker. On a disturbed day, or on the low bands near sunrise, the long path can be much stronger.
- Calling without listening. If the DX station is beaming long path to your region and you call on the short path, you may never be heard. Listen to who is getting through.
- Ignoring the echo. An echo is information. It tells you two paths are open and that one of them may be better.
- Using the wrong bearing. Long path bearings need an accurate great circle calculation from your own location. A map that is not centred on you will mislead.
The Bottom Line
Long path DX is not exotic; it is simply the other half of the great circle. When the short path is closed by darkness, absorption or aurora, the long path may still be open, especially along the gray line and on paths to stations far away. Learn both bearings to the regions you chase, swing the beam when a signal is weak or shows an echo, watch sunrise and sunset at both ends of the path, and keep notes on what works from your location. The reward is contacts that most of your neighbours never notice are possible.
Frequently Asked Questions
What is long path DX?
Long path DX means making a contact along the longer of the two great circle routes between two stations, going the opposite way around the Earth. It works when the ionosphere along the long route supports the band while the short route is closed or weaker.
How do I calculate the long path bearing?
Add 180 degrees to the short path bearing. If the result is more than 360, subtract 360. The short path bearing itself should come from a great circle calculation from your exact location, such as the one many logging programs show for each callsign.
Why do I hear an echo on some DX signals?
An echo usually means the signal is arriving by both the short path and the long path. The long path signal travels further, so it arrives a fraction of a second later. Turning a beam towards the stronger path often reduces the echo.
Which bands are best for long path?
Long path can appear on any HF band. On the low bands it is usually linked to darkness and the gray line, and openings can be short. On the higher bands it more often follows paths through daylight. Conditions vary with season and the solar cycle.
Can I work long path with a dipole or vertical?
Yes. A vertical hears all directions, and a dipole’s two main lobes point in opposite directions, so it covers the short and long path to a region at the same time. You cannot choose between the paths, but you can time your operating for known openings.
What is skew path?
Skew path is propagation that does not follow either great circle route. The signal is refracted or scattered away from the direct path, so it peaks at an unusual bearing. If a signal is strongest somewhere between the short and long bearings, skew path is a likely explanation.