The Amateur Amateur: Dallying on the Digital Modes
By Gary Hoffman, KB0H
digital-mode experience likely would have been able to identify the
particular signals by their distinctive sounds, but I just clicked on
the mode buttons until something intelligible began appearing on the
August 22, 2005
The MMSSTV screen. Note the vital Auto button.
Many pictures I received were unreadable or scrambled.
In my last two
columns I explained how curiosity about PSK31
prompted me to figure out how to run digital modes on my HF
transceiver. Initially there was a certain amount of puzzling and
fumbling, but once things started to work, it was like opening the
door to a whole new world! Digital modes are kind of addictive.
Something about running the whole show from my computer appeals to
Once again I'd
like to thank all those swell Amateur Radio operators who wrote all
that really nifty computer software that is necessary to make digital
modes work. Without their labor and generosity far fewer hams would
be using these fun modes.
I started out
with the intention of just trying PSK31, but I noted that options
included in some of the PSK31 programs made it just as easy to try
other digital modes. Well, it was just too tempting. I just had to
sample some of them.
Not being all
that familiar with who does what and where in the digital world, I
just scanned through the digital subbands until I heard something
that sounded like data. Hams with digital-mode experience likely
would have been able to identify the particular emissions by their
distinctive sounds, but I just clicked on the mode
until something intelligible began appearing on the screen. Most
signals I encountered were PSK31, but I did stumble across a RTTY
conversation or two. Some of the software would even handle Morse
code, but I seldom tried that. Somehow using a computer to decode
Morse felt a bit like cheating.
But others came out near perfect.
accident I discovered that there was a fledgling emergency digital
net active in Missouri. It used MFSK16
format, which incorporates more error-correction features than PSK31.
I had not tried MFSK16 before, and it took just a little bit of
experimenting before I got it right. Soon I was able to check into
the Missouri Emergency Digital Net. Participation was light, and the
net seemed to fade away, but I suspect that it will be revived as
more hams get involved in digital modes. I hope so. I rather enjoyed
hearing the cheerful warble of MFSK16 data coming over my
discovered that slow-scan television (SSTV)
was just as easy to send and receive as all of the other HF band
digital modes. As with PSK31, RTTY, and such, free software was
available to send and receive SSTV. With no additional equipment, I
should be able to transmit my own pictures over the air. Now that
was just irresistible. I quickly downloaded and installed the
freeware program called MMSSTV
Written by Makoto
Mori, JE3HHT, MMSSTV
is a marvelous piece of computer code. It
has all sorts of options which, on initial inspection, baffled the
heck out of me. Just staring at the MMSSTV screen it became obvious
to me that there was not just one
format for sending SSTV
pictures, there were several
. They had evocative names such as
Robot 36, AVT 90, Scottie 1, and Martin 2.
I still have no
clue as to what all that means. Fortunately I didn't need to know,
because the program had the one magic button all novices seek, the
one marked "Auto."
The next trick
was to find SSTV signals on the air. I scoured my collection of band
plans and wrote down everything that mentioned SSTV. I checked all of
the frequencies I'd assembled and ascertained that I was most likely
to find SSTV aficionados
on 20 meters around 14.230 MHz.
As with any new
ham radio endeavor, I listened first--or, in this case, watched.
Luckily for me MMSSTV
didn't require a lot of user
intervention. It managed to grab signals out of the air, decide which
formats had been used and interpret them.
first picture was quite an experience. The noise coming from my
transceiver was reminiscent of special effects from a science fiction
movie. But even more fascinating was the image being assembled line
by line on my screen. It didn't look like much and it was full of
static and lines that weren't contiguous, but it was still
recognizable as a picture. I flopped back in my chair with my mouth
hanging open and marveled at it. It was a wondrous moment. I suspect
that every SSTV operator felt that way when his or her first image
dallying with the digital modes. I monitor the occasional PSK31
conversation. If I hear some data stream making unfamiliar music with
tones I'll play around to see if I can decode it. But more and more
often I find myself camped out on 20 meters hoping to pull in some
static-ridden, but still beautiful image via SSTV.
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
Readers are invited to contact the author via e-mail,
© 2005 American Radio Relay League