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KRA 405B RADAR ALTIMETER INSTALLATION MANUAL
Page 2-19
006-10536-0010 Rev. 10 Oct/2005
f. Place a one (1) foot square or larger piece of the mi-
crowave absorber over each KRA 405B Antenna. The KRA
405B should unlock and the Indicator pointer should
drive clockwise behind the mask.
NOTE: It may be necessary to remove the aircraft
from the hanger, away from other aircraft
and/or other sources of reflection in order
to achieve an unlock condition (pointer be-
hind mask) with the microwave absorber.
While keeping the Antennas covered with the microwave
absorber, reconfirm that the self-test is operational
by repeating steps b. through d. above. Release the
test switch. The pointer should again go behind the
mask.
g. If the indicator pointer does not stow behind the mask
in Step f. above, check for a faulty RF cable or TNC
connector at the R/T by exchanging the antenna coaxes
cables at the R/T. Repeat Step f.
If the pointer still does not stow, disconnect the an-
tenna cable from the R/T unit’s receiver port (upper
connector) and terminate the receiver port with a 50 ohm
load. Load the transmitter antenna into the RF absorb-
er. The indicator pointer should stow behind the mask.
Repeat this test for the transmitter port (lower port),
and again the indicator should stow behind the mask.
Note which R/T port, when terminated, causes the indi-
cator needle to stow, and continue troubleshooting in
that direction.
If the R/T will not stow the indicator needle with ei-
ther the Transmitter or the Receiver port terminated
into a 50 ohm load, the R/T unit should be bench tested.
If the indicator pointer can be stowed with both ports
terminated, reinstall the correct cables on the trans-
mitter and receiver ports and remove the cables at the
antenna.
Terminate these cables into the 50 ohm load one at a
time while placing the microwave absorber over the other
antenna.