IEEE Consumer Electronics Magazine - April 2017 - 97

Next, a transmitter-receiver radio, operating at 144 MHz, is
used as the human-to-radio interface. The radio has a microphone
for voice (transmit) and a speaker for audio (receive). The
144 MHz combines (adds 10,224 to 144 to arrive at the operating
frequency of 10,368 MHz, or 10.368 GHz) in a circuit called a
mixer, shown in the center of the diagram. During receive, incoming radio signals at 10,368 MHz enter the equipment via the
antenna. It follows the frequency chain backward: instead of multiplying, the frequency is being divided, and the result is sound
from the radio speaker. In transmit, the signals originate as voice
from the microphone, and the path goes outward along the path.
There are several problems to overcome when designing,
building, and operating equipment for the microwave bands. To
send effective ham messages, radio signals need to be multiplied
with each other to become strong enough to cover desired distances. Thus, because of the high number of multiplication stages, frequency accuracy is difficult to achieve. Small errors add up and
can be significant when arriving at the final, operational frequency.
Radio circuits require stability to remain steady on a particular frequency. This is important because a receiving station must
be able to find and hold onto the transmitted signal. When a
radio system is unstable (drift), the frequency will wander above
and below the desired frequency and thwart communications.
If two microwave stations attempt to contact each other, they
may miss a connection if Station 1 is drifting up in frequency
when Station 2 is drifting down in frequency. In this case, making
a contact between Station 1 and Station 2 will be difficult, if not
impossible. Sometimes hams will use Morse code when there is
not enough bandwidth to send a voice message. Because Morse
code signals occupy a narrower bandwidth than voice signals, it
is able to overcome marginal or weak signal conditions.
Due to the issues that arise with multiplication, stability,
drift, and bandwidth, microwave ham communication has
challenges. Hams take pride in setting distance records-and
in breaking them. In 2007, Wayne Yoshida set a record for
completing the longest two-way ham radio contact on 10 GHz
using Morse code: 1,448 km/899 mi, from central California
to Baja, Mexico [11], [12]. Unfortunately, his record did not
last long. Just a few minutes later, another ham broke that distance record by a few kilometers.
Hacking computer hardware and software to control radios and other ham equipment started as soon as affordable
personal computers were available. The Arduino and Raspberry Pi series of microcomputers are now being used for
amateur radio projects to generate frequencies, in motor and
motion control applications, to encode and decode Morse
code, in switching applications, and in electronic test and
measurement instruments for radio stations [13].

hams working at TRW (now Northrop-Grumman) in Redondo
Beach, California, and Foothill College (Los Altos Hills, California) and other hams [14]-[16]. OSCAR-1 was a simple, oneway transmitter (a radio beacon) that beeped out a Morse code
message familiar to hams all over the world, HI. (For ham radio
operators, HI is the Morse code abbreviation for laughter.).
Since then, amateur radio satellites have been launched by
several countries, each designed, built, and tested by teams of
students, engineers, and others in their spare time. Ham radio
satellites fly as ballast, or piggyback, payloads on launch
vehicles at little to no cost to the ham radio operators. Space
agencies allow ham radio payloads because they understand
the educational value of ham radio activity. Nearly 20 operational OSCAR satellites, in various forms, are now in orbit
and service to the amateur radio community, providing various ham radio functions. A summary of some active ham
radio satellites in orbit, including live reports, is posted on the
Radio Amateur Satellite Corporation (AMSAT) website [17].
One interesting feature of many amateur radio satellites is
the antenna material: a metal tape measure is cut up and used to
make antennas for the satellite. The tape measure antenna can
be folded or rolled into a compact shape and is stowed until the
satellite is launched. When the satellite is launched into orbit,
the tape measure antenna springs out to its full length. It is
simple, lightweight, and reliable.
The parts shown in Figure 5 will be used for a position
location beacon for a high-altitude (near space) balloon.
This package, when completed, may reach altitudes in the
hundreds of thousands of feet. The number one record for a
GPS-reported maximum altitude achieved by a high-altitude
balloon is 147,647.60 ft, in July 2016 [18].
AMSAT is the nonprofit, educational organization dedicated
to fostering amateur radio in space [19]. Similar organizations
are located throughout the world, such as AMSAT-DL in Germany,

BeYOND THe STArS
Hams are not just experimenting on Earth. For many years, ham
radio operators have been exploring with space-related spectrum topics. For example, on 12 December 1961, just four years
after the Russians launched Sputnik-1, an amateur radio satellite
was launched. In 1960, Orbiting Satellite Carrying Amateur
Radio (OSCAR)-1 was designed, built, and tested by a team of

Figure 5. A metal tape measure can be made into an effective and
reliable antenna for space and near-space vehicles. The items shown
are for a high altitude, near-space balloon experiment. From left:
An old portable ham radio transceiver, with parts removed to
reduce weight, a data modem, and a GPS module. (Photo courtesy
of Wayne Yoshida.)

APRIL 2017

IEEE Consumer Electronics Magazine

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