The Amateur Amateur: The HF Chronicles--A New Mode of Thinking
By Gary Hoffman, KB0H
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.
September 6, 2002
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
signal, or it may simply be electromagnetic belching from the planet
Jupiter (a little hyperbole there; we call that "contributing
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
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).
When Iono is asleep he leaves your transmissions alone.
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
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
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 dis
believed 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
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.
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