Genesys GDR- COM Series, Installation Manual, Page: 31 / 62

GDR-XXXX NAV/COM INSTALLATION MANUAL
CHAPTER 2 – SYSTEM INSTALLATION
64-000109 Page 31 of 62
18. ANTENNA LOCATION
A. COM Antenna
The GDR requires a 50 Ohm vertically polarized COM antenna compliant with
TSO-C169. The COM antenna should cover the COM frequencies appropriate for
your model number. Some possible antennas are listed in Table 7, Table 8, and
Table 9.
•
Use RG-400 or equivalent, not to exceed 2 dB of signal loss.
•
The COM antenna should be mounted on the centerline of the airframe, at
least 3 feet from other antennas.
•
In multiple GDR installations, one antenna should be mounted on the
bottom centerline of the airframe and the other antenna should be mounted
on the top centerline of the airframe.
•
Avoid sharp bends of the coax.
•
Do not route the COM coax near ADF antenna cables.
•
Maintain at least a 2 foot distance between COM and NAV coaxial cables
when routed parallel to each other.
CAUTION:
•
The installer must ensure that the antenna is placed such that radiation
exposure to aircraft personnel is limited to 0.2 mWatt/cm
2
to conform to the
FCC safe exposure limit. This may be measured or calculated. For direct
line of sight spacing the following formula may be utilized:
𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃
𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸
=
𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃
𝐸𝐸𝑒𝑒𝑒𝑒𝐸𝐸𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝐸𝐸
4 𝜋𝜋𝑅𝑅
2
𝑚𝑚𝑚𝑚 / 𝑐𝑐𝑚𝑚
2
In this formula, R is the distance from the antenna. The effective transmit
power is found by adjusting the transmitter power for the antenna gain in
milli-Watts. For a 25 Watt radio with an antenna gain of 3 dBi, the
corrected transmit power is 49,881 mW. This gives a minimum safe
distance of 141 cm.
Table 7: List of VHF COM Antennas
Vendor Part Number Maximum Airspeed Freq. Range
Harris
DM C60-1 Not specified "Blade" 118-137 MHz
Comant
C109 Not specified "whip" 118-137 MHz
Harris
DM C63-1/A Not specified "whip" 118-137 MHz
Harris
DM C70-1/A 400 mph "Blade" 118-137 MHz