The Amateur Amateur: The HF Chronicles--A New Mode of Thinking

By Gary Hoffman, KB0H
Contributing Editor
September 6, 2002

We continue to discover the wide, wide world of HF and, among other things, how SSB is different from VHF and UHF repeater operation and why headphones often are necessary to domestic tranquility.

My last column was about setting up my new HF (high-frequency) transceiver. This time we'll learn about the first discoveries I made with it.

It was immediately apparent that the HF bands were nothing at all like the VHF and UHF bands that I had been using. I had been operating with FM exclusively and had gotten used to clear, strong signals. The HF bands were completely different.

There was a bewildering array of emission modes available on the HF bands. You've got your AM, your RTTY, your USB and LSB and, of course, CW and sometimes others. Using FM had been a lot like searching for brightly colored Easter eggs on a well-manicured lawn. Using AM and single sideband, however, was more like hunting for mushrooms in a dense forest. Some of the noise that I was hearing may be a signal, or it may simply be electromagnetic belching from the planet Jupiter (a little hyperbole there; we call that "contributing editor's license").

When I listened to an FM receiver, signals typically were either there or not there. The strength of a signal was indicated by how clear it was, not by how loud it was. AM and single sideband operations were just the opposite, I discovered. Weak signals could be extremely clear but barely audible. Strong signals could blow the headphones right off of my skull!

Cartoon Gary listening to earphones

Seeking a deeper meaning in the static. [Illustrations by the author]

Ah, yes. Headphones are necessary to keep peace in a household. Whereas the static-filled background noise might be tolerable--even enjoyable--to the amateur trying to contact Antarctica, to the rest of the family it's like listening to a garbage disposal trying to digest gravel. Sweaty ears may be uncomfortable, but they're not nearly as uncomfortable as talking to a divorce lawyer.

Some hams working VHF and UHF bands take those bands--and their propagation--for granted. Those bands always seem to be there. Ah, but the HF bands, well, sometimes they disappear. I could bore you with a long-winded technical explanation, but I won't. Here is what really happens. You see, way up in the sky there is a great demi-god named Iono. Things are very strange up in Iono's "sphere of influence." Propagation is good at night. That's because Iono is asleep and will leave your transmissions alone. When he wakes up the next day, however, he's hungry, and he'll eat your radio waves. (It's a fact--in a manner of speaking, that is. You can look it up.)

Working the HF bands, I also noticed that frequency selection is not "channelized." VHF and UHF transceivers usually dial frequencies in specific increments, but HF transceivers will happily let you operate on any frequency, such as 7.150001 MHz. I don't think most ham operators deliberately operate on such hair-splitting frequencies, but sometimes it is necessary to dial them in to get the best reception.

All of the things I've mentioned might lead you to believe that the HF bands, and indeed any emission modes other than FM, are quite inferior. But the radio-savvy among you know that the big advantage is that HF band radio waves go much farther than VHF and UHF band radio waves. So instead of talking to Charlie a couple of miles away, you can talk to Vlad in Transylvania. It is, in fact, difficult to tell how far a signal has traveled unless the ham operator at the other end tells you where he is. A clear, loud signal might originate hundreds of miles away, while a relatively quiet signal might be coming from just across town. This is not just due to Iono fooling around with the radio waves. Antenna types and orientation have a lot to do with it (more about this in a future column).

Iono asleep

When Iono is asleep he leaves your transmissions alone.

Iono asleep

But when he wakes up, he's hungry and he will eat your radio waves.

Since HF radio signals travel a considerable distance, it is relatively easy to pick up foreign stations. This is a mixed blessing, however, since the Amateur Radio frequency allocations are not always quite the same in every country. It is not unusual to find that Iono is snoozing and that radio propagation is good on a HF band, but that a foreign shortwave broadcast station is blasting megawatts across most of it. This is especially true on the 40-meter phone band, which we have but Europe doesn't.

Another peculiarity about the HF bands is overlapping signals. FM transceivers are subject to "the capture effect." That is, the strongest signal will "grab" the receiver, and all other signals will be excluded. This is not true of AM and single sideband. Overlapping conversations are quite common. Some of the overlap is due to stations that simply cannot hear each other using the same frequency, and some of it is due to stations on different, but close-by, frequencies. Have you ever been to a party where you can hear a lot of conversations going on but can't make out a thing that is being said? Same thing on a busy HF band.

I would be remiss not to mention Morse code. I did listen to Morse code conversations and even transmitted a few dits and dahs myself. Supposedly this emission mode is "easier to pick out" among the static and the noise and the overlapping signals. Well, the straight dope from The Amateur Amateur is . . . that's true! I never actually disbelieved those tales, but I was amazed when I found that I really could discern and decipher weak Morse code signals buried in static. It wasn't even particularly difficult to pick out a particular Morse code conversation among a multitude of overlapping ones, as long as the pitch of each signal was slightly different--that is, they're on slightly different frequencies.

So, what did I learn? I learned that operating on HF would require an entirely different mindset--a different way of thinking. I would have to think globally instead of locally. I would have to consider the entire band and several bands at that, not just the local repeater frequencies. I would have to be more aware of the band plans, of which there seems to be plenty. I would have to figure out when Iono took cat naps. And above all, I would have to get used to listening to lots and lots of static.

I just hoped that my brain (and ears) were up to it.

Editor's note: ARRL member Gary Hoffman, KB0H, lives in Florissant, Missouri. He's been a ham since 1995. Hoffman says his column's name -- "The Amateur Amateur" -- suggests the explorations of a rank amateur, not those of an experienced or knowledgeable ham. His wife, Nancy, is N0NJ. Hoffman has a ham-related Web page. Readers are invited to contact the author via e-mail [email protected].

© 2002 American Radio Relay League


E-mail Gary Ross Hoffman

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