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Page 5-10 400 SERIES MAINTENANCE MANUAL
Rev. C P/N 190-00140-05
5.6.1 Com Setup Page Fields
5.6.1.1 Com Frequency
The Com Frequency field selects a VHF communication frequency. For purposes of setting the
squelch, sidetone levels and mic gain, only the frequencies 118.000, 127.000, and 136.975 MHz
can be used.
If any adjustment is made at one of these frequencies, it should
be made at all three frequencies.
5.6.1.2 Frequency Spacing
8.33 kHz channels are not authorized for use in the United States.
SELECTION DESCRIPTION
25.0 kHz Selects traditional 25 kHz spacing (760 channel)
8.33 kHz Selects 8.33 kHz channel spacing, which is required in certain areas of the world
5.6.1.3 SQ 250
For GNS 430 units with serial number 96300200 or lower, the operation
of the SQ 250 setting is reversed. The higher the SQ 250 number, the
more signal is required to break squelch. For units with serial number
lower than 96300200, units may contain –03 Com Boards. See Section 1
for 28V unit part numbers.
The SQ 250 field sets the noise squelch threshold for 25 kHz channel spacing operation. The
squelch threshold can be set to any value between zero and 63.
25 kHz ___________ OK
5.6.1.4 SQ 833
The SQ 833 field sets the squelch threshold for 8.33 kHz channel spacing operation. The squelch
threshold can be set to any value between zero and 63. The higher the number, the more signal is
required to break squelch.
8.33 kHz ___________ OK