communications and for the automated information
exchange systems. The UHF receiver separates the
receive band (302 to 312 MHz) from the transmit band
(248 to 258 MHz).
The receiver translates the received carriers to
intermediate frequencies (IFs) in the 20-MHz range and
separates them into one of three channels. One charnel
has a 500-kHz bandwidth, and two have a bandwidth of
25 kHz each. The signals are filtered, hard limited,
amplified to an intermediate level, and up-converted to
the transmit frequency. Each channel is then amplified
by one of three high-power transmitters.
GAPFILLER also supports the FLTSATCOM
system secure voice system and the fleet broadcast in
the UHF range. The GAPFILLER communications
subsystem will eventually be replaced by the
There are four FLTSATCOM satellites in service.
These satellites are positioned at 100° W, 72.5° E, 23°
W, and 172° E longitudes. They serve the Third, Sixth,
Second, and Seventh fleets and the Indian Ocean battle
groups. These four satellites provide worldwide
coverage between 70° N and 70° S latitudes (figure
Each FLTSATCOM satellite has a 23-RF-channel
capability. These include 10 25-kHz channels, 12 5-
kHz channels, and 1 500-kHz channel. The 500-kHz
and the 10 25-kHz channels are reserved for Navy use.
Of the 10 25-kHz channels, channel 1 is used for the
fleet broadcast. All charnels use SHF for the uplink
transmission. SHF is translated to UHF for the
There is a separate UHF downlink transmitter for
each channel. Each of the 23 channels has 3 different
frequency plans in which the uplink or downlink may be
transmitted. This capability precludes interference
where satellite coverage overlaps.
The latest generation of Navy communications
satellites is leased; hence, the program name LEASAT.
As we mentioned earlier, these satellites replaced 2 of
the 3 GAPFILLER satellites and augment the
CONUS LEASAT (L-3) is positioned at 105° W
longitude, LANT LEASAT (L-1) is positioned at
Figure 2-5.FLTSATCOM coverage areas,