Honeywell KHF 1050 System Installation Manual page 137

If using the KHF 1050 Maintenance Program, some variation in indicated
pressure from one reading to the next is normal. Averaging multiple readings
is recommended.
In the event that the pressure leaks to a point below approximately 4 psig (27
kPa gauge) between annual maintenance checks, more frequent monitoring of
the pressure in that antenna coupler is advisable. If the rapid pressure loss
persists, service on the coupler is suggested to check for leaks.
NOTE: Gauge pressure readings and Maintenance Program pressure
readings can differ by up to 3 psig (21 kPa) due to the effects of
temperature and barometric pressure at the time the readings are
taken. Averaged multiple readings from the Maintenance Program is
the most accurate method for determining the pressure of the KAC
1052.
10.A.(3) KAC 1052 Pressure Warnings
In the event the pressure drops significantly below the normal value, a Label
351 Coupler-Pressure-Warning bit is set so that it can be used to advise the
pilot that the KAC 1052 should be serviced soon (typically repressurized). For
example, with a PS440 controller "PRS W" appears on the display when bit 15
is set (and bit 28 is zero). During the Coupler Pressure Warning the KHF 1050
system will continue to operate normally. A Pressure Warning indicates that the
antenna coupler may be approaching a Pressure Fault condition.
10.A.(4) KAC 1052 Pressure Faults
In the event the pressure drops to a level where there is a risk of arcing inside
the antenna coupler, both bits 15 and 28 of Label 351 are set. This can be used
to indicate to the pilot that a Coupler-Pressure-Failure condition exists. With a
PS440 controller, "PRS F" appears on the display when both bits 15 and 28 are
set. During the Coupler Pressure Fault, the KHF 1050 system will automatically
reduce the transmitter power to 50W PEP, regardless of the transmit power
selected by the pilot. This reduced power will in turn reduce the RF voltages
seen inside the antenna coupler. The low-power condition will be reflected in
transmitter power bits 22 and 23 of Label 037, Word 1, output by the KRX 1053
being set to 00B (MIN Power) as long the Coupler Pressure Warning exists. As
a practical matter, the inside of the antenna coupler would have to experience
an altitude typically above 5k ft MSL to issue a Pressure Fault.
Revison 2
N
KHF 1050 SYSTEM INSTALLATION MANUAL
23-10-09
Page 2055
Apr/2006