GDU 37X Installation Manual Page 3-5190-01054-01 Revision C3.3.3 Buried Antenna (below the skin covering or glareshield) MountingThere are potential performance issues related to buried antennas that the kit builder/installer should beaware of prior to electing to install a buried antenna. See also Section 3.6.3, Non-structural Installation toGlareshield.• Some gain of the antenna may be lost as the signal needs to penetrate through the skin of the aircraft.The loss may not be apparent, but under the some of the worst case signal scenarios signal availabilitymay be affected.• The materials in some aircraft are not suitable for GPS signals to penetrate, care should be taken toproperly modify the aircraft structure to accommodate this. Modifications of this sort are not recom-mended or inferred by Garmin or the installation of the GDU 37X, and the installer should seek theguidance of the kit manufacture for such modifications.• XM – FIS antennas may typically be buried without performance impact if the overlying material isfairly transparent to the satellite signal.Figure 3-2 shows example areas of some mounting locations which have been used. Low satellitereception and tracking are compromised in these installations due to fuselage and tail blockage. It is notpossible to determine the full impact of these locations, however initial flight testing has not shown anysignificant impact to availability, your results may vary.Figure 3-2 Carbon/Glass Buried Antenna Area
