B KRA 405
Rev 6, June 2003 IM 006-00104-0006.dwd Page 2-6
prep #33 (P/N 016-01127-0000) to cleanse the metal of any residue left after
removing paint or insulating material. Protect bare aluminum surfaces with
Alodine 1001 (P/N 016-01128-0000) or equivalent prior to mounting antennas
or bonding straps.
2.4.3.C.2 RF/AIR SEALING GASKETS ARE TO BE INSTALLED BETWEEN KA 54A
MOUNTING FLANGES AND AIRCRAFT SKIN.
2.4.3.C.3 RF ANTENNA CABLES SHOULD BE PREPARED ACCORDING TO PARA-
GRAPH 2.4.4 of the KRA 405 Installation Manual, using the 40 foot AID, if
possible.
2.4.3.C.4 MAXIMUM ALLOWABLE LENGTH FOR EACH RF CABLE (RECEIVE AND
TRANSMIT) IS 17 FEET. System sensitivity suffers when cables longer than
17 feet are used.
2.4.3.C.5 MAKE SURE THE CABLE ARE TIGHT INSIDE THE CABLE CONNECTORS.
2.4.3.C.6 AVOID THE USE OF RIGHT ANGLE OR BULKHEAD COAX CONNEC-
TORS. SWRs are greater on these types of connectors and therefore can
cause problems. If right angle or bulkhead connectors must be used, extreme
care should be exercised in assembly and the tests in paragraph 2.5 should
be performed.
2.4.3.C.7 MINIMUM RECOMMENDED BEND RADIUS OF RG 393/U COAX IS 5 INCH-
ES. Bends less than 5 inches in radius can significantly increase VSWR.
2.4.3.C.8 EXCESS CABLE LENGTHS SHOULD BE LASHED SECURELY BUT NOT
TO THE POINT OF CUTTING OR DISTORTING THE CABLE INSTALLA-
TION. Cutting the coax shield causes an altitude return and affects system
operation.
2.4.3.C.9 TIGHTEN ALL ANTENNA COAX CONNECTORS SLIGHTLY MORE THAN
FINGER TIGHT.
2.4.3.C.10 DO NOT PAINT ANTENNA
: Operation and/or accuracy may suffer.
2.4.4 ANTENNA CABLES
2.4.4.1 General
The KRA 405 Radar Altimeter System is designed to read an altitude of zero (0) feet
at touchdown by adjustment of antenna cable length and selection of the proper Air-
craft Installation Delay (AID). Depending upon the minimum length of cable required
and the antenna height above the ground at touchdown, the proper AID can be select-
ed.
2.4.4.2 Minimum Cable Length Required
After the location of the antennas has been determined (paragraph 2.4.3), a minimum
length of antenna cable required for the installation can be determined. Measure the
distance from the R/T to each antenna adding enough extra length to avoid obstruc-
tions in the cable path and to allow for connection to the antenna connector.
RELEASED FOR THE EXCLUSIVE USE BY: AIRCRAFT ELECTRONICS ASSOCIATION
UP536434
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