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KHF 1050 SYSTEM INSTALLATION MANUAL
Page 2037
Revison 2 23-10-09 Apr/2006
5.E.(4) EXTERNAL MODEM AUDIO Output from Receiver/Exciter
(J10531-42 & 62)
The receiver/exciter provides an unsquelched, EXTERNAL MODEM AUDIO
Output that is a balanced output for use by an external modem. This output is
factory adjusted to provide 0.775 VRMS +/-5% (1 mW) into a 600 ohm load, and
is active when the receiver/exciter is receiving in any modulation mode. If
necessary, this output can be adjusted by a service adjustment located on the
top of the Receiver Exciter. See “10.B. Field Alignment” for the location of this
adjustment. Accessing this adjustment requires removing the dust cover
5.E.(5) External Modem Audio Input High/Low- (J10531-42/62)
EXT MODEM AUD INPUP H/L
The audio signal level is typically 0.775 VRMS across 600 ohms.
The KRX 1053 Receiver/Exciter presents a balanced, floating 600 ohm load to
this signal.
This input does not present direct-current bias to the signal source.
There is no audio clipping or compression associated with this input at normal
operating levels.
This input is factory adjusted so that 1 KHz modem input signal of 0.775 VRMS
yields nominal Data USB output power from the KRX 1053 Receiver/Exciter.
5.F Discrete Inputs and Outputs
5.F.(1) Key Event - (J10531-13) KEY EVENT
The KRX 1053 Receiver/Exciter asserts (grounds) the KEY EVENT discrete
output when the transmitter is activated by any activation method.
This output may be used by external equipment, such as a flight recorder, to
sense when the HF system is transmitting. Maximum sink current is 100 mA.
5.F.(2) Maintenance Test- (J10531-78) MAINT TEST
When the MAINTENANCE TEST discrete input is asserted (grounded), the
KRX 1053 Receiver/Exciter RS-232 Maintenance port accepts test commands
from the KHF 1050 Maintenance Program (P/N 222-31044-0000).
This input is continuously read.
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