Technical Articles

Guide to Low-Band DXing– When and Where

Most Hams start out DXing on the HF “high bands” of 20 through 10 meters. There are lots of stations active, the antennas are manageable in size and effective height, and when there are sunspots to light up the ionosphere, the bands open up for stations large and small. At some point, though, one’s curiosity is piqued by those mysterious “low bands”—30 through 160 meters. (“Top Band,” 160 meters, is really in the MF range, but we’ll consider it part of the HF low bands here.) They have a reputation for being “hard,” but maybe not as much as you think. Here are some tips to get you started. Warning: Low-band DXing, like a lot of challenging activities, can be all-encompassing!

What Makes Low-Band DXing Different?

When you first dive below 14 MHz and start trying for DX contacts, don’t be surprised if you find yourself “in the dark” about what works and what doesn’t. (That’s a pun you’ll get later…) Sure, the techniques for operating in pileups and making all your gear run smoothly still apply—perhaps even more so than on the high bands—so you have a running start.

The most obvious difference is that the low bands open up in the very late afternoon and really get going after dark. When this column was being written (early 2020), the sunspot cycle was at a minimum with very low solar flux. That meant the high bands closed down quickly at sunset, if they even opened through the day at all! You probably hear the experienced Hams talking about how no sunspots is actually good for low-band DX, and that’s true.

The limits on ionospheric skip below 14 MHz are not whether the ionosphere’s F layer can return your signal to Earth but whether the lower D layer absorbs your signal. Through the day, the D layer acts like a big RF sponge—that’s why you can’t hear distant AM stations until after dark when they start coming in by sky wave, just like Ham Radio DX. So the low-band DXer gets going around sunset and loses interest around sunrise.

Noise levels are typically much higher at low frequencies as well, making it harder to hear the DX station than it would be on the high bands. There is usually enough received signal from even the most distant stations, but atmospheric and man-made noise often covers them up. You can fight noise with directive antennas, noise canceling devices, and by knowing when to listen for the best signals. 

Listening to the World Turn

Part of the fun of low-band operating is that you really can hear the world turning! Especially at sunrise or sunset at your location or the DX station’s, short openings often occur that are quite strong. These are often “spotlight” openings that favor one specific region, and it might not be where you expect, so be ready! Learn about the dawn enhancement when signal strengths can go up by a few S units for a short time as the sun rises on the eastern end of the path. Use a gray line program like the one shown from W3WVG (below) to keep an eye on sunrise and sunset around the world.

You’ll also want to stay aware of solar activity and the geomagnetic field (GMF) here on Earth. Be aware of temporary enhancements when a coronal mass ejection impacts the Earth’s GMF. Flares and other phenomena can have a big effect on low-band propagation. Sites like NOAA’s Space Weather Prediction Center and spaceweather.com have a lot of information for the DXer on any band.

Starting Your Journey in the Station

You probably already have most of the in-station equipment needed to work low-band DX. Modern radios work just fine! 100 watts will get you started although you’ll need to pick your battles and be patient at times. An amplifier helps you get through pileups a little faster, but lots of DX has been worked “barefoot” (sans amplifier). An antenna tuner is useful for matching antennas at the low end of the HF bands where the DX stations are easiest to find.

Get to know your receiver’s filtering and noise management controls. Because of the lower signal-to-noise ratio (SNR), you’ll have to use every feature of the DSP to get rid of noise and reject QRM from nearby stations. A noise reduction (NR) system can help reject noise crashes and pulses, keeping you fresh and engaged with the signal, not the noise. Learn all about passband tuning, notch filters, attenuation, and RF Gain. A DSP audio enhancer like the SOTABeams Wolfwave (above) helps you hear better and lowers fatigue from hours of listening, too.

On the transmitter side, you need to make sure you’re not leaving any dB on the table. Is your keying crisp without creating key clicks? Is your transmit audio clean and punchy so it can be heard as clearly as possible on “the other end”? Can your transmitter stand the high duty cycle of the digital modes, and have you set the audio levels just right? Distortion on any mode not only loses some of your watts in spurious products, it also makes your signal modulation hard to decipher. That’s not a good thing when you are trying to work an already weak station on a noisy band.

It would be a good thing to learn CW (Morse), if you haven’t already, since that mode gets through a lot easier than phone, particularly for a smaller station. FT8 and FT4 are other popular choices that perform very well at low SNR. Many DXpeditions are focusing on FT8 or FT4 instead of RTTY for their digital mode operating—they simply work more stations using those modes! Learning how to operate all three modes— phone, code, and digital—will ensure you always have something to work.

Your Low-Band Antenna System

Outside the shack, it may be surprising to find that you don’t need 200-foot towers with full-size rotatable beams (although it helps) to work DX stations. There are three basic things to optimize on the budding low-band DXer’s antenna farm:

  • Low-angle signals
  • Matching and radiating
  • Minimizing losses

Let’s start with the last one first. You need to make sure as few of your watts as possible go to warming the feed line or “heating the worms.” While a tuner in the station may be able to turn a high SWR into a nice 50Ω impedance, the SWR in the feed line is still high, leading potentially to surprisingly high losses. If you can, adjust your antenna feed point impedances so they are close to 50Ω or use an external automatic tuner

Remember that matching is not necessarily radiating! If you do use a tuner in the station, open-wire feed line has lower loss than coax under most circumstances, so use a balanced tuner or one with a balun at the output. Try to use antennas that are efficient as well. There are lots of designs to experiment with!

Finally, DXing on any HF band will be the most successful with antennas that radiate low-angle signals.  On 40 and 30 meters, it’s not too hard to get a dipole, one of the best antennas ever, installed at a half-wavelength above ground or higher where your signal will be launched at the low vertical angles that result in the loudest signal far away. Sloping dipoles are another option that works very well and even gives you a bit of directivity.

On 160, 80, and 60 meters, you’ll probably use a vertically polarized antenna. A tried-and-true solution is a ground-plane antenna like the Butternut HF2V dual-band 80-40 meter vertical over a ground plane of 30 or more radials.

If you have a tower, you may be able to use it to support half-slopers, where both the sloping wire and tower radiate. Many low-band DXers shunt-feed their tower as a gamma-matched vertical. For all vertically polarized antennas, a good ground radial system is required to minimize ground losses. (Graphics from the ARRL Antenna Book provided courtesy of the American Radio Relay League.)

Getting that Low-Hanging Fruit

Okay! You’re putting out the watts and listening for those rare-sounding signals. You can get a great start and begin to hone your low-band DX skills by picking some of the “low-hanging fruit” on the bands.  For starters, here in North America there are quite a few DX stations one or two “hops” away, no matter where you live. Everything in CQ zones 1-9 is quite workable under most conditions. Remember that Hawaii (KH6) and Alaska (KL7) count for DXCC!

Contests

DX contests are a great way to put low-band contacts in your log and find out when you have the best chances of making them. You’ll find the HF bands loaded with loud, workable signals as soon as the contest starts, although you’ll have to stand in line awhile at first as the big stations work each other.  Friday night can be frustrating for small stations, but beginning Saturday morning, the pileups thin out and that’s your best chance.

You can operate in the Assisted or Unlimited categories to help find stations and get used to where the activity is during the various events. Of course, everybody else can be in those pileups along with you, but you do learn about propagation and what you can expect to hear from your location. Another good way to learn is to enter as a Single Band competitor. By staying on one band, you really learn how it sounds and when it opens to different areas.

DXpeditions

There are plenty of DXpeditions to exotic places around the world with many not far from the U.S. and Canada. The rarer entities can generate enormous pileups, but toward the end of the operation, many groups are looking specifically for stations that haven’t made a contact yet, particularly on the low bands. Those last few days can be very productive for logging new ones.

Less-rare locations are a little easier to work and there are lots of them not too far away. The Caribbean islands are numerous and often very loud around North America. The northern countries of South America and West Africa can be surprisingly strong due to salt water paths, especially at their sunrise. The IOTA (Islands On the Air) program also generates a lot of activity through expeditions to activate the various salt-water island groups. Special event stations with unusual calls are fun to chase, too. 

Useful References and Resources

This short introduction is more of an enticement than a cookbook, but you can start whipping up your own recipes in short order. The low-band DXer quickly becomes a student of propagation and antennas, keeping an eye on potential station activations as well. Writing as someone who started DXing in the pre-internet days, I can assure you that there is a wealth of information to help you in your quest!

Books

The low-band DXer really needs to have a copy of ON4UN’s Low-Band DXing. Now in its fifth edition, John Devoldere’s book covers propagation, antennas, and techniques like no other. On those nights while you’re waiting for the DX to pop out of the static, it will keep you informed and thinking about ways to improve your station and your operating.

Antennas are probably the number-one station characteristic making the difference in working the DX.  Even the small station can put up surprisingly effective antennas, and there is a wealth of time-tested designs.  Along with Low-Band DXing, the ARRL publishes the ARRL Antenna Book and the Antenna Compendium series.  These will get you wandering around your station looking for places to plant and grow your antenna farm.

Bulletins

Finally, you need to know who’s on from where and when they will be active. W3UR’s Daily DX comes out every single day with information about DX activity, especially on the low bands. KB8NW has been publishing the weekly online OPDX Bulletin for years, and you can subscribe at no cost. The ARRL also publishes propagation bulletins every week on Friday with predictions and interesting observations and tutorials. For contests, expeditions, and other happenings on the bands, NG3K takes in all of the “We’re going here!” announcements and compiles them into a single table for easy reference so you don’t have to miss a single one!

I hope this article has whetted your appetite to try out those “bands of mystery” where the DX lurks in the nighttime hours! There’s a lot to be learned and enjoyed, just as when you started chasing DX on 20 meters. It’s one of the most rewarding activities in Ham Radio!

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