GTS 8XX/GPA 65 Installation Manual
Page 2-7
190-00587-00
Revision 4TP
2.4.1 Coaxial
Cable
The GTS 800 requires two sets of coaxial cable assemblies and the GTS 820/850 requires three sets of
coaxial cable assemblies when a directional GA 58 antenna (or other Garmin approved antenna) is used
for both top and bottom. Each set consists of four coaxial cable assemblies.
Each set of four cables must be assembled using the same type of coaxial cable in order to meet phase and
attenuation matching requirements. In order for the system to operate in compliance with manufacturer
specifications, the coaxial cable assemblies must not exceed the attenuation specifications as stated in this
document. This section explains in further detail the coaxial cable and termination requirements.
2.4.1.1 GTS 800 Installations
NOTE
A monopole antenna is required if installing an optional bottom mounted antenna on all
fixed-gear aircraft. Retractable-gear aircraft can use either a monopole or a directional
bottom mounted antenna.
A GTS 800 installation with both top and bottom mounted directional antennas uses one set of coaxial
cables for the four GTS 800 TOP jacks (J1 TOP, J2 TOP, J3 TOP, J4 TOP) that are connected to the
corresponding top antenna jacks J1, J2, J3 and J4. A second set of coaxial cables are used for the four
GTS 800 BTM jacks (J1 BTM, J2 BTM, J3 BTM, J4 BTM) that are connected to the corresponding
bottom antenna jacks J1, J2, J3 and J4. Each cable assembly shall not exceed the maximum attenuation
of 2.5dB at 1090MHz as shown in Figure 2-1.
Figure 2-1. GTS 800 Installation with Top and Bottom Directional Antennas
If an optional bottom mount monopole antenna is installed, a single coaxial cable must be used to connect
the GTS 800 bottom jack J1 BTM to the monopole antenna jack. The coaxial cable assembly shall not
exceed the maximum attenuation of 2.5dB at 1090MHz as shown in Figure 2-2 and stated in Table 2-4.
Each of the remaining GTS 800 bottom jacks (J2 BTM, J3 BTM, J4 BTM) are to be terminated using a
QMA 2 watt termination as specified in Table 2-2.