Installation Planning and Considerations
190-01810-00
GDL 82 TSO Installation Manual
Rev. 5
Page 4-3
Consider the following modifications to help reduce loss in the transponder system, if the results of the procedure in
table 4-1 do NOT meet the minimum performance specifications of Part 43, Appendix F. Any of the steps, or their
combination, can be used.
NOTE
Performance of any or all of the following recommendations does not necessarily ensure compliance
with 14 CFR §43, Appendix F.
•
Replace transponder coaxial cable and connectors with MIL-C-17 type F low-loss cable (e.g., RG-400 or RG-393).
For older installations it may be necessary to replace the existing coaxial cable assembly with a low-loss cable type
to pass the transponder ramp check in accordance with Part 43, Appendix F. Refer to section 6.2 for specifications
of recommended coaxial cable.
•
Ensure the existing transponder and L-Band antenna are properly installed in accordance with manufacturer’s
specifications (e.g., units are properly grounded, the coaxial cables are adequately routed and that the L-Band
antenna ground plane is appropriate). Any corrosion in the coaxial cable connection, or ground plane will
diminish performance.
•
Ensure the existing L-Band antenna meets the minimum performance specifications. New L-Band antenna maybe
required. Refer to section 4.4.1 for specifications of acceptable L-Band antenna.
•
Due to the nature of antenna radiation patterns, nulls or marginal conditions may be observed when measuring
a utilized radiated signal from the aircraft. In these cases, tests from different positions should be performed to
determine an acceptable angle for measurement.
•
If the existing transponder is Class A (i.e., operational ceiling is > 15,000 feet), but the results of the existing
transponder system check meet only the requirements for Class B equipment (i.e., operational ceiling is < 15,000
feet), the operating ceiling can be limited to 15,000 feet MSL if deemed acceptable. This method does not affect
the transponder’s equipment certification, but it does limit the aircraft’s operating ceiling based on the overall
system performance specifications under 14 CFR §91.215. Placards and/or an entry in the aircraft’s AFMS
specifying the limitation must be made.
4.3 GDL 82 External Sensors and Devices
ADS-B equipment requires GPS/SBAS data for ADS-B Out transmissions. The following GPS/SBAS data sources (and
their software versions) may be used with the GDL 82:
GDL 82 internal GPS/SBAS with approved GPS antenna
GTN 6XX/7XX series navigators with software v6.21 or later
GNS 4XXW/5XXW series navigators with software v5.30 or later
GNS 480 navigator with software v2.4 or later
