User's Manual Part 1

T
2
CAS / Part No. 9000000
SYSTEM DESCRIPTION AND INSTALLATION MANUAL
34-43-20
15 Feb 2003
Use or disclosure of information on this page is subject to the restrictions in the proprietary notice of this document.
2--4
This is summarized with several examples in the Table 2--1 below, assuming 4 unique
installations.
Table 2--1. Coax Cable/Connector Loss
Assumed
Antenna
Gain (dB)
Minimum
Cable And
Connector
Loss(dB)
Maximum Cable
And Connector
Loss(dB)
Cable
Length
(feet)
Recommended
CableType(and
loss)
(Cable Length (feet)x
Loss) + Connector
Loss= Cable and
Connector Loss
30 30 -- 29 = 1 30 -- 12.5 = 16.5 10 311601 (0.11 db/ft) (0.11*10)+1=2.1
30 30 -- 29 = 1 30 -- 12.5 = 16.5 100 311601 (0.11 db/ft) (0.11 * 100) + 1 = 12
26 26<29=>0 26 -- 12.5 = 13.5 10 311601 (0.11 db/ft) (0.11*10)+1=2.1
26 26<29=>0 26 -- 12.5 = 13.5 100 311601 (0.11 db/ft) (0.11 * 100) + 1 = 12
In the above examples, the antenna gain and assumed losses effectively stay within the
desired minimum and maximum ranges.
High--quality coaxial cables should be used because a mismatch in impedance, possible
with lower quality cables, produces reflections in the cable that increase signal loss.
Losses due to cable mismatch should be considered in the maximum cable loss budget.
The coax must meet FAR part 25 specifications for environmental conditions.
Recommended antenna mounting location
(1) The GPS antenna should be installed close to aircraft centerline with minimum
deviation from the aircraft level horizontal position. The antenna location is on the top
side, front half of the aircraft fuselage to minimize the shadowin g effect of the vertical
stabilizer and wings.
(2) The GPS antenna should be installed at least 39 inches (1 meter) away from any
other non L-- band or L--band except as mentioned below.
(3) If a SATCOM transmitting antenna is installed, the GPS antenna should be located a
minimum of 160 inches (4.064 meters) away.
(4) For a dual GPS antennae installation, the separation should be a minimum of 12
inches.
(5) If a TCAS or VHF communication transmitting/receiving antenna is installed, the GPS
antenna should be located a minimum of 48 inches (1.219 meters) away.