Northern Airborne Technology NPX138 - Manual (Page 38)

NPX138 Panel Mount Radio Manual SM41 Rev. 4.00
3.4.3
Scan/Guard TX Switch
When this switch is in the SCAN position, the radio will begin scanning. See section
3.10 for further details on scanning.
When this switch is in the GD TX position, all radio transmissions will be on the guard
transmit frequency instead of the transmit frequency of the current channel. The radio
continues to receive on both the Guard and Main receivers. This function only applies
to radios with the guard receiver option installed. If not, the radio will display ‘GD NOT
INSTALLED’ on the upper line when the switch is set to the GD TX position.
Set this switch to the NORM position to disable scanning. All radio transmissions will
use the transmit frequency of the current channel.
3.4.4
Guard Controls
Guard
Select
Switch
Guard RX Indicator Guard RX Volume Control
The guard controls are functional only in radios with the optional guard receiver
installed.
The rotary knob independently sets the guard RX volume. In most models, there is no
‘Off’ detent position. On most NPX models, even with the guard RX volume set
completely counterclockwise, the operator will still hear activity on the guard channel (at
the preset minimum level).
The Guard Select switch (marked GD1/GD2 on the faceplate) selects the active guard
channel. For standard guard receiver modules (-x5x), the first guard channel (GD1) has
a receive frequency of 168.625 MHz and the second guard channel (GD2) has a
receive frequency of 167.950 MHz, as specified by the USFS. Radios with custom
guard receiver modules are available (-x6x). For radios with synthesized guard modules
(-x7x), the receive frequencies for both the GD1 and GD2 channels are programmable
via the front panel or serial load to any frequency in the range of 138.000 to 173.995
MHz in 5.0/6.25 kHz increments. The transmit frequencies of the guard channels are
programmable. The Guard RX LED indicator lights amber when there is activity on the
selected guard channel.
Page 3-4 Nov 10, 2003
ENG-FORM: 806-0105.DOT
Amendment # 4 Jun 1 0, 2005
CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIRBORNE TECHNOLOGY LTD.