Revision 4 - December 17,1998 Ryan TCAD 9900 Series Page 6-1
SECTION VI
INSTALLATION PLANNING AND
TROUBLESHOOTING GUIDE
6.1 GENERAL
The following information is designed to give the technician guidance in planning
installations and efficiently troubleshooting problems with the TCAD. If there are any
problems or difficulties experienced in installing or maintaining the TCAD, please contact
the factory. Your input is invaluable.
6.2 EXTERNAL CONNECTIONS
6.2.1 ANTENNA
The antenna should have, at minimum, a ground plane equal to one-half wavelength (half-
wavelength is about six inches) all around the antenna.
The antenna should be mounted as far forward as practical, above the cockpit, with no
appurtenances between the antenna and the nose of the aircraft. Optimum location of the
top antenna is important, because threatening traffic is normally detected ahead of the
aircraft. Placement at this location also to allows TCAD to properly correlate with the
pilot’s observations.
Since the transponder signal from the threat aircraft is essentially line of sight, traffic ahead
of the aircraft will be blocked if the antenna is mounted well aft of the cockpit. If the
antenna is blocked by the airframe, other antennas, or large metal mass such as an engine,
a less than optimum antenna reception pattern will occur. A perfect location does not
exist on an airplane, and some compromise is normally necessary. Nonetheless, the
TCAD antenna should be at the highest, forward-most part of the aircraft when the
aircraft is in level flight. The forward view from the TCAD antenna should be better than
the view from the cockpit. Since the TCAD monitors for traffic all around the aircraft,
insure that the antenna is clear to the rear also.
Customer satisfaction is directly related to proper antenna location.
Ground the antenna to the airframe. Otherwise, the ground plane is not effective.
A second antenna supplements the coverage of the top antenna. It is normally placed on
the underside of the fuselage. In rare situations (such as some helicopters), where there is
an obstruction behind the antenna, the second antenna could be located on the other side
of the obstruction. Before this is done, contact the factory.
The cable lengths for each antenna should be about the same, within 0.2dB of each other.
Sometimes a KA-60 King-stamped pulse antenna is substituted for a clean antenna. The
KA-60 is electrically acceptable for the 9900 and 9900A. However, field reports indicate
the antenna can warp when mounted on top of the aircraft. In addition, the upside down
King stamp shows on the top antenna for all to see that the installer took a shortcut.
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