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2016 Extra Class study guide: E2A - Amateur radio in space

Posted: 17 Mar 2016 07:23 AM PDT
http://feedproxy.google.com/~r/kb6nu...m_medium=email

E2A Amateur radio in space: amateur satellites; orbital mechanics;
frequencies and modes; satellite hardware; satellite operations;
experimental telemetry applications

Working the satellites is a very popular amateur radio activity. There’s
even an organization dedicated to launching and operating amateur radio
satellites AMSAT (www.amsat.org).

Perhaps the most important thing you need to know when trying to
communicate via satellite is where the satellites are. One way to predict
the location of a satellite at a given time is by calculations using the
Keplerian elements for the specified satellite. (E2A12)

Amateur radio satellites are not in a geostationary orbit. That is to say
they are constantly changing position in relationship to a point on the
Earth. The type of satellite appears to stay in one position in the sky is
geostationary. (E2A13)

When determining where a satellite is, you might want to know its orbital
period. The orbital period of an Earth satellite is the time it takes for a
satellite to complete one revolution around the Earth.(E2A03)

It’s also important to know the direction in which it is travelling. The
direction of an ascending pass for an amateur satellite is from south to
north. (E2A01) The direction of a descending pass for an amateur satellite
is from north to south. (E2A02)

Next, you need to know what mode the satellite is in. The term mode as
applied to an amateur radio satellite means the satellites uplink and
downlink frequency bands. (E2A04)

We use a combination of letters to denote the mode. The letters in a
satellites mode designator specify the uplink and downlink frequency
ranges. (E2A05) If it were operating in mode U/V, a satellite’s receive
signals would be in the 435-438 MHz band. (E2A06) U stands for UHF, V for
VHF. With regard to satellite communications, the terms L band and S band
specify the 23 centimeter and 13 centimeter bands. (E2A09)

Satellites repeat signals using transponders. Transponders are similar to
repeaters, except that they receive signals across a band of frequencies
and repeat them across another band of frequencies. The most common type of
transponder is the linear transponder. All of these choices are correct
when talking about the types of signals can be relayed through a linear
transponder (E2A07):

FM and CW
SSB and SSTV
PSK and Packet


One thing to keep in mind is to keep your transmitter power to the minimum
needed to hit the satellite. Effective radiated power to a satellite which
uses a linear transponder should be limited to avoid reducing the downlink
power to all other users. (E2A08)

There are quite a few interesting phenomena that result from the fact that
satellites rotate while they are orbiting. One reason the received signal
from an amateur satellite may exhibit a rapidly repeating fading effect is
because the satellite is spinning. (E2A10) To mitigate the effects of this
of fading, you might use a circularly polarized antenna. A circularly
polarized antenna is the type of antenna that can be used to minimize the
effects of spin modulation and Faraday rotation. (E2A11)

Sending up high-altitude balloons with amateur radio equipment has also
become a popular part of the hobby. The balloons send telemetry data with
various measurements, such as pressure and temperature, and GPS data to
track their positions. The position data is sent using APRS (Automatic
Packet Reporting System), which is the technology used to track, in real
time, balloons carrying radio transmitters. (E2A14)

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