As a radio engineer, you probably have had some experience with
satellite reception. In the United States most of the radio networks
are on the radio community satellite, currently called AMC-8. General
Electric, who used to operate GE-8, sold the satellite division to
SES-Americom. The radio networks that operate a carrier on AMC-8
include Westwood One, ABC, Premiere, Clear Channel/NSN, Jones,
Learfield Communications, WITF Radio Pennsylvania, Peninsula
Communications, Morris Communications and Waitt Radio. The advantage to
being on the same satellite, operating in the same polarity (all are
vertically polarized on odd transponders) is that only one dish and a
single LNB are required for most networks.
While AMC-8 sees the bulk of the radio activity, other satellites
that carry programming, mostly for regional, state or sports networks,
include Clear Channel's AMC-1, AMC-2, AMC-4 and PAS-8 and NPR's Galaxy
C-band (3,700MHz to 4,200MHz) is used for the national networks
because of the robust reception. Direct TV or Dish Network users know
what rain fade can do to a signal. C-band is less prone to fading due
to bad weather because it is lower in frequency than Ku and uses a
larger dish. Kuband frequencies are about 10,900MHz to 12,750MHz, with
DBS using 11,750MHz to 12,500MHz.
Relative locations for several commonly
Downlink equipment includes a dish, LNB and cable run to a receiver
or multiple receivers with audio and data ports to feed the
First, let's look at the antenna. The FCC has allowed satellite
operators to put satellites in the sky every two degrees. If your dish
is not two-degree compliant, you may receive interference from an
adjacent satellite. To get enough signal for minimum fading, use a 3.2
meter or larger solid-core dish for AMC-8 reception. The SES-Americom
website at www.ses-americom.com is an excellent resource for
information to line up a dish, including a tool to determine azimuth
and elevation based on a Zip code. AMC-8 is low on the horizon from the
East Coast, so you must be clear of buildings or trees.
If a dish is placed on top of a building or in a higher location to
obtain a clear line of sight, be aware of any terrestrial microwave
paths that operate in the 4GHz range that could potentially interfere
with reception. Conduct a frequency search to be sure. Comsearch is one
company that can provide this service. Once you've cleared the downlink
site, it is possible to file with the FCC to protect the downlink, in
the event another applicant wants to install a terrestrial microwave
path or uplink nearby, after the dish has been installed.
Think inside the box
Are you peaking your dish when the satellite is in the center of the
box? Geostationary satellites fly in a figure-eight pattern in the sky.
When aligning a dish, do so when the satellite is at the center of that
figure eight. This is called center of the box, and the satellite
owner's website lists when the satellite is at that point. If aligned
when the satellite is at the far end of the figure eight, it is
possible to get a significant drop in signal strength when it reaches
the other side.
Don't use the receiver to align the dish. With the latest digital
receivers, it can take 30 seconds or more for the receiver to acquire a
signal. It is better to align a dish with a spectrum analyzer. If you
don't own one, find someone at the local TV station or cable company
who will let you borrow one. You can also rent one if necessary.
Another option is to hire a local satellite installation company. Many
carry accurate signal meters. If using a spectrum analyzer to line up
the dish, contact the operator of the satellite for a printout of the
satellite carrier pattern. They can tell you what pattern to look
One more option is to purchase a lower-cost test device. Similar to
a spectrum analyzer but designed to operate in the 920MHz to 2,150MHz
range. Emitor makes a unit called the Satlook Digital. This unit can
download the carrier pattern for the satellite and alert you when the
dish is aligned properly.
Specify an LNB that has a phase-locked loop (PLL). Older video LNBs
will will pick up a signal, but the digital receiver will not lock and
drop out every few seconds. A good LNB with low noise temperature will
make a big difference in how well the receiver will work. Find the
lowest noise temperature possible for best performance.
Most networks use Starguide receivers. Other receiver types include
Comstream, Wegener, International Datacasting and ICP.
Westwood One transmits a Starguide II signal, which any Starguide II
and many Starguide IIIs will receive. ABC, Premiere and Jones use
Starguide III transmission, which can only be received by a Starguide
III receiver. Because these receivers can only receive one network at a
time, many radio stations have multiple receivers. It is not
recommended to use one receiver to pick up multiple networks because
the programming done at the network head-end is lost each time the
carrier or provider is changed.
When connecting more than one receiver to the dish, only one
receiver should power the LNB. Splitters are available that will pass
voltage on only one and block the dc on the others. Only use passive
splitters. Amplified splitters can introduce phase distortion or
possibly overload the receiver.
Specify a phase-locked-loop LNB
with a low noise temperature. Photo courtesy of Patriot Antenna
The downconverted L-band signal from the LNB can be connected via
RG-6 for long runs or RG-59 for short runs. Avoid in-line booster
amplifiers; they can overload the front end of the Starguide receiver
and degrade the signal. Sometimes the receiver may see too much signal
even without an amplifier, requiring an inline pad to be inserted
before the receiver.
A great utility program written by Kirk Wesley to test a Starguide
receiver is found on the Radio magazine website in the
Engineer's Notebook section. The software was designed as a
relay logger, but it will also display bit rate errors and signal
The Starguide signal meter displays EB and AG values. EB, short for
Eb/No, is a ratio of energy-per-bit to spectral-noise density;
basically a signal-to-noise reading for a digital transmission system.
Generally, the higher the EB the better the quality of the signal. AG
is an abbreviation for automatic gain control. The better the AG, the
lower this reading. You can only compare these readings between
receivers using the same version of software. If the versions are
different, the readings can vary due to different components used in
later versions of the hardware. Don't worry about different signal
readings from one receiver to the next. As long as the EB is above 4.5
and the AG is between 130-192, the receiver should work fine.
Trautmann is senior vice president of engineering for Westwood
One Radio Networks, New York.