58 May 2015
Data transmissions vary in complexity and contain a
wide variety of information. Some are as simple as Morse
code (CW) or Radio-teletype (RTTY), while others are
more sophisticated such as AMTOR or SITOR which are
similar to RTTY.
Some of the popular newer modes are Binary Phase
Shift Keying (BPSK), Weak Signal Propagation Reporter
(WSPR), and the weak signal digital modes JT65/9. These
modes — developed by amateur radio operators — use low
power and complex coding, and allow communication
over great distances. Text messages are usually conveyed
with these protocols. To convey images and graphics,
commercial stations use radio-facsimile (FAX), while
amateur stations use slow scan TV (SSTV) and EasyPal.
One of the things that all of these modes have in
common is that they are audio modes. That is, the radio
signals are first converted to audio signals using your radio
receiver. Then, the sound is analyzed using audio
decoders in the PC software. Figure 2 shows how the
pieces fit together.
What makes this setup work nicely is that most PCs
have sound cards that can accept the audio signals from
the radio. If yours does not, you can add an inexpensive
USB sound card to do the job. Then, to decode the audio,
it is only a matter of selecting the right software for the
mode of interest.
Several software packages will be discussed to help
you get started. The good news is that most of it is free
and can be
your radio are that it
be stable, have a numerical frequency readout, and
receive SSB (single side band) signals. Many commercial
or ham radios will do the job, but can be expensive. One
popular low cost receiver that fits the bill is a DEGEN
Model DE1103 as shown in Figure 3. It can be found on
the Internet for around $62 and works well in this
This model stabilizes in a few minutes, has a jack for
an external antenna, has digital frequency readout, and a
BFO (beat frequency oscillator) for receiving SSB signals.
Its small size and battery operation make it easy to take
on vacations along with your laptop PC. This allows you to
enjoy the hobby away from home.
Setting Up Your
The single most important component of your setup is
the antenna. Ideally, it should be a resonant antenna such
as a dipole that is cut for the frequency range of interest.
However, a long wire antenna placed as high as possible
will work well even if it is not perfectly matched. The main
thing is to get it up high and away from noise sources, like
The DE1103 has an external 3. 5 mm antenna jack on
the side of the case for shortwave. Unlike more costly
radios that provide a 50 ohm antenna jack, the DE1103
impedance varies from 1,000 ohms at 4 MHz to 200
ohms at 14 MHz. You can use a single wire or shielded
coaxial cable to connect your antenna to this jack. If you
use coax, you will need to make a cable with a 3. 5 mm
plug on the end. To reduce noise, an antenna tuner or
pre-selector can be used between the radio and the
A good ground system is very important. Try to
connect your radio ground to the earth ground in your
home. Failing that, use a long wire along the floor to act
as a counter-poise or substitute for earth ground.
Connecting the Audio
The audio signal from your radio needs to be
connected to the PC sound card line-input. If you are
using an external USB sound card, use a USB cable with
FIGURE 2. Block diagram of shortwave data receiver.
FIGURE 3. DEGEN Model 1103 SSB radio.
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