Revision 4 - December 17,1998 Ryan TCAD 9900 Series Page 6-4
6.2.7 TRANSPONDER COUPLER
The Coupler consists of a 50-ohm track on the transponder line and a diode detector to
provide a signal to the TCAD indicating the host transponder has transmitted. No
maintenance is required for the coupler.
If the coupler signal fails to reach the TCAD, the unit will detect and display the host
transponder.
The most important item regarding the Coupler is the proper mounting and installation of
the connectors on the transponder antenna cable. The RF cable must be intact and it
should have no bends that exceed the natural radius of the cable. Do not run the Coupler
output line with any pulse lines, such as the transponder RF lines.
Improper or poor transponder antenna connector installation, or cable damage may result
in a Signal Fail indication on the TCAD or display of the host transponder.
The type N connectors used with the coupler are designed for RG-58 cable. If the
connectors are used on cable that is smaller than RG-58, the cable jacket may not provide
sufficient mechanical support for the connector. In this case the shield and the center
conductor mechanically support the connector, resulting in an unreliable connection. The
coax can easily pull out, creating transponder or TCAD problems (seeing the onboard
transponder). Be sure the coax jacket is sufficiently snug in the connector in order to
provide mechanical support and a more reliable connection.
The Coupler should be well grounded to the airframe. Grounding to the side of the
TCAD or transponder rack is usually not sufficient.
Addition of the Coupler to the Antenna cable increases the cable length, and can cause the
transponder frequency at the antenna to shift. Adjust the transponder as necessary.
6.2.8 INPUT TO TCAD DISPLAY AND PROCESSOR DISPLAY LINES
Twisted shielded pairs should be used. Excessive noise from the aircraft penetrating these
lines can cause a Link Failure indication on the TCAD Display. A % link is provided on
the self-test. It should always be 90% or better.
6.2.9 INSTALLATION WITH MULTIFUNCTION DISPLAYS
The Multifunction Display Interface for the ARGUS is approved under STC 00900NY.
For instructions regarding installation, see Model 9900B Multifunction Display Interface
Installation Instructions, Document 32-2304. Use twisted shielded pairs for the RS-232
connections.
When interfacing with an Argus Series Moving Map (Multifunction) Display, remote
INFOrmation and SELect buttons are very desirable. An ADF/Remote switch will give
the pilot the ability to deselect the ADF and select the TCAD.
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