W8WWV - Opinions on Low-Band Operation

Greg Ordy


This page contains my opinions on the challenge of low-band operation, and why I find low-band operation to be a whole lot of very interesting fun. By low-band, I mean 160 meters (1.8 MHz - 2.0 MHz), 80 meters (3.5 MHz - 4.0 MHz) and to some extent, 40 meters (7.0 MHz - 7.3 MHz).

One of the major goals in the amateur radio hobby is to make two-way radio contacts. All of the time and money is ultimately spent so that somebody can make a two-way contact. For me, the question becomes, what are the challenges and obstacles to overcome in order to make the contact?

In order to answer that question, we must supply some more information. In particular, what band and mode are being considered, and what part of the world do we want to contact?

I must confess, I am really ignorant about the bands above 50 MHz. Actually, I have recently been spending a lot of time on 6 meters (50 MHz - 54 MHz). That band, the magic band, has its own character and charm. But with that recent exception, the VHF and UHF bands are all substantially unknown to me. Some of what happens up there looks very interesting. Moon bounce, meteor scatter, satellites, repeaters, fast scan TV, all of that, and more, looks like a lot of fun, and a good challenge. I guess that at the end of the day, my first interest in the hobby came because of shortwave contacts. To this day, I am still mainly interested in the shortwave (1.8 MHz - 30.0 MHz) bands.

These bands (160, 80, 40, 30, 20, 17, 15, 12, and 10 meters) are mainly distinguished by their propagation possibilities, which are related to the wavelength of the signal, and the interaction of the signal with the ionosphere. When conditions are right, that two-way contact can be on the other side of the earth. On some bands, those conditions may occur almost every day. On other bands, they may occur only a few days each year, or even on certain years that track part of the 11 year sunspot cycle. These are external constraints that are simply handed to the shortwave radio operator.

And now, finally, I have said enough so that I can separate the bands into two groups. For me, on 20 meters through 10 meters, the challenge is to be louder than some other amateur in the pile-up. On the lower bands, however, the challenge is to beat the atmospheric noise and understand the propagation. It is simply my own personal nature to prefer to compete against myself and nature as opposed to other people. When I say compete against myself, I mean, can I continue to refine and improve my station and skills. In effect, can I beat myself, as opposed to other radio operators.

The line I have drawn is obviously not pure or perfect. Pile-ups certainly are common place on all bands. Propagation rules all bands. But I would claim that, in general, working a certain station on the upper short-wave bands is more often accomplished by being louder (or more rude) than another station, as opposed to being at the right place at the right time with the right equipment and techniques.

All of the bands and modes and styles have something going for them. For me, I find that at this point in my radio career, I am attracted to the lower short-wave bands. They are a great place to ragchew with the locals, as well as chase rare DX.

Essential Elements

Before I set out on a rambling set of web pages, covering all sorts of topics, I do want to try and give my overall perspective of operation on the low bands. These are very general comments, based upon my own experiences, and all of the information that I have been able to discover and read.

Much of the DX activity that happens on the low bands surrounds gray line propagation. Gray line occurs when one or both sides of a QSO (conversation) are in either sunrise or sunset. At these times, signal strength often peaks, and contacts are briefly possible that are otherwise impossible. During the daylight hours, the effect of the sun on the D-layer of the ionosphere effectively causes it to absorb low band signals. This means that from shortly after sunrise, until shortly before sunset, the lower bands will (typically) be closed for DX activity. At other times of day (at night!), however, successful low band operation requires that you become aware of gray line propagation. Fortunately, there are many software packages as well as written materials that cover all aspects of understanding and exploiting gray line.

A complete QSO requires the ability to transmit and receive. On most of the amateur radio bands, a single antenna is used for both directions. On the low bands, however, it is quite common that separate antennas are used. For transmitting purposes, it is desirable to have an efficient antenna with a low primary angle of radiation. The classic dipole, unless very high in the air, tends to have an unacceptably high angle of radiation. The vertical antenna can have very good (that is, low) angles of radiation, but the challenge becomes trying to keep the efficiency of the vertical high. This leads into the much debated world of ground radial systems. A 1/4 wavelength vertical for 160 meters is approximately 120 feet tall. Since this is beyond the height limit (due to cost or space) of many amateurs, much work has been spent on making a shorter vertical more efficient. Broadly speaking the transmit antenna should have the highest efficiency and highest gain possible. Even with an efficient transmit antenna, it is very desirable to run as much power as legally allowed.

On the receive side of the equation, the key is to improve the signal to noise ratio of the antenna (system). Within reason, antenna gain on reception is not important. What is important is to separate the signal from the noise. While claims have been made that some antennas have certain special properties that make them immune to noise, I'm of the school of thought that says that the primary  mechanism involved in improving the signal to noise ratio of a receive antenna system is the narrowing of its response pattern. Interest in this area has led to my S Meter Lite program, which helps measure the noise level of various receive antenna systems.

Given my experiences, my pages will tend to concentrate on issues related to vertical antennas and arrays of vertical antennas, as well as receiving antennas.

I have put together a set of low band references on my Resources page.

Does a dB Matter?

One of the questions that I believe all amateur radio operators must answer for themselves is: does a dB matter? The dB (decibel) is an interesting word in that it has two primary definitions.  One is a mathematical definition, and the other is a subjective definition. The subjective definition is that one decibel is a just noticeable difference between two signal levels. In terms of power, the mathematical definition says that you have a one dB reduction in power when you reduce a given power level from 100 percent down to approximately 79.3 percent. To be very practical about it, if I had a 100 watt transmitter, and started to reduce the power while transmitting, I should have to get down to 79 watts before a listener believes that that have heard a difference in signal strength.

As we go about building our stations, there are many places where we make decisions that will influence the strength of our signal. Obviously the power output of the transmitter defines an available power level. On the way to the antenna, we go through some sort of transmission line, which will introduce loss. At the antenna, our choice of antenna begins to matter. What type is it (dipole, Yagi, vertical, etc.)? How high is it? What objects are nearby? What is our local terrain? Are we behind a mountain? What are the characteristics of the soil in our area?

Usually, we can reduce loss (or increase gain) at any step in the process by spending more time and/or money. For example, we could spend more money on a lower loss transmission line, and perhaps save that one dB. Does it matter?

If we operate on 40 meters with some regional friends, and all signals are 10 dB over S9 with a background noise level of S3, we appear to have many more dB than we need, if the goal is to stay above the noise level. How many more contacts are we going to make if we increase our strength by exactly one dB? How many less will we make if our signal is reduced by one dB?

I think it is entirely possible to construct an argument that says that one dB does not matter. If you can save some money on transmission line, and only lose one additional dB, perhaps that's a sensible trade-off. If you don't want to take the time to tune up your transmitter, and you are putting out only 80 watts, not 100 watts, perhaps that doesn't really matter.  If it would take another hour of standing in the rain to get the end of the dipole up another 20 feet in the air, and if that would only make a one dB difference in the signal level, perhaps you should just go inside and get out of the rain. After all, one dB is, by definition, the just noticeable difference.

I believe that if all that was involved was a single dB, one absolute dB, my personal answer would be that a dB doesn't matter. I find, however, that this question is more about my attitude and philosophy towards paying attention to details. When put in those terms, a dB does matter. If one is not careful, one dB can lead to two. And two can lead to three. And at three dB, we have thrown away half of our transmitter power, or half of our received signal. Now, that seems just wasteful to me, even if I'm already 20 dB over the noise level.

So, my own personal answer to the question: does a dB matter?, is: yes, it does. What I really am trying to say is that I want to be aware of the detailed operation of my station, and I will spend time, effort, and money, to reduce loss and increase gain. Sooner or later, a set of small improvements can and do make a difference.

If I look out at my buried transmission line going to my tower, and figure that it would take several afternoons of work, and $150 (USD) to replace it with a cable that would have 1 dB less loss on 10 meters, I might decide to just skip it, after all, it's just one dB. But if next year I would increase the height of my tower, I could pick up a second dB (in certain circumstances). Maybe in the third year, I could replace the antenna with one with just one more dB of gain. Taken one at a time, all of these changes are just one dB, and maybe one dB just doesn't matter. But the combined result is significant. I will be able to make more contacts, work more DX, dig out more weak signals, and enjoy all that goes with a more capable station. It may take years to get enough time and money to make all of the changes, but it places the emphasis on the journey, not the destination.


As long as I am spouting opinion, I would like to comment on the practice of tail-ending. Tail-ending is the most common case of the general idea of transmitting at a time when everybody else is listening, for the purpose of having the DX station copy your call in the clear. Hopefully, they will come back to you as their next contact. In general, I find this practice to be distasteful, rude, and I don't do it.

Of course if tail-ending didn't exist, then a DX station would select the next station to work based solely upon that station's signal strength. The strongest station would indeed be the next one worked. To be most negative about it, tail-ending is a trick which can be used when your signal strength alone doesn't cut it.  Since I believe that a dB does indeed matter, I hope that it's at least consistent that I would want the determination of stations worked to be based upon signal strength (not tricks).

The problem with tail-ending is chaos and time-wasting. Another form of tail-ending, which is more understandable, but just as wasteful, is when local stations call the DX station over and over and over again, hoping that they are heard simply because others stop calling. They hope to end up in the clear just because everybody else stops transmitting. The DX station probably identified a call very quickly, but has to wait until everybody stops calling. This problem can be dealt with by using split-frequency operation. The trade-off here is that we improve our contacts per unit time ratio at the expense of consuming much more bandwidth. Split-frequency operation also opens the door to a wide range of tactics and strategies which are all acceptable (in my opinion, which is what this page is), and I do them myself. The most common being whether to sit and transmit on a single frequency and wait for the DX to find you, or, to attempt to understand how the DX stations is working the pile-up and shift your frequency to where they will be listening.

Tail-ending  can be best minimized by an experienced DX operator who knows how to keep control of their situation and makes contacts at a rapid rate. Sadly, this skill is more rare than it should be. I personally enjoy listening to a good DX operator who works stations quickly and fairly. The main skill required is to structure the QSO exchange so that it is clear when the DX station is listening for new calls. Other operators who toss out their call in the middle of an existing QSO are just plain lids, and there are too many of those around. My biggest personal gripe in this area is the DX station who ends a short QSO in the middle of a pile-up with confusion to the extent that nobody knows if they should call. DX stations really should use a consistent QSO format that clearly ends with a QRZ, or some other indication that it is time for the next contact.  The CW protocol can be different, but the concept is the same. And all of the rest of us should keep our transmitters off until we are invited to transmit, and when we do transmit, two or three complete callsigns should be enough.

Another pet peeve of mine is stations that send incomplete callsigns, but I'll leave that for another page. That page can include my opinion of the DX-police, and on the interesting phenomena of local stations that call DX stations when they obviously can't even hear the DX, but are hoping against hope for some miracle of QSB.

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Last update: Wednesday, December 31, 2003 07:15:31 PM
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