Northern Airborne Technology THxxx - Manual (Page 104)

Tac/Com Control Head Manual SM06 Rev. 4.10
3.9.1.3 LIST+PRIORITY Scanning
In this mode, both LIST & PRIORITY features are combined, so that a list can be
checked while still periodically testing for activity on two priority channels. This is a new
feature and only exists on software revisions 2.13 and later for Tac/Com II, and 1.45
and later for Tac/Com I controls. In this case, priority allocations remain per the normal
priority mode, but list channels have a lower priority than the 'home' channel, and are
scanned only when there is not any activity on the other three.
Note for NTX Transceivers:
When CTCSS tones are enabled, the access time for the decoder is added to the LIST
+ PRIORITY scanning time, dramatically reducing receive audio intelligibility. NAT
therefore recommends that the combination of CTCSS tones and LIST + PRIORITY
scan should be avoided for these units.
3.9.1.4
AM Scanning
While this was not an original feature of Tac/Com and the NT136-PAS multi-mode
transceiver, it is now fully implemented. Some hardware updates are required to the
transceiver (below s/n 1018) to achieve the required sensitivity for fast-lock AM
reception, but coupled with current software, it can provide scanning with AM levels
down to 2.0 uV. Because of the electrically noisy environment aircraft present, squelch
thresholds must be much higher for AM receivers than for FM (2-3.0 uV versus 0.5 uV).
When scanning, the effective range of coverage will be smaller for AM than for FM
signals of the same strength.
3.9.1.5
Scanning on other systems
On Midland Syn-Tech I radios, channels added to the scan list will have the letters 'a' or
'b' added to the end of the ID label display. The status line is used to select whether list
'b' or both list 'a' and 'b' are used in the SCAN mode. Only list 'a' channels are used in
the priority mode. Scanning is not provided for Wulfsberg radios due to their very long
synthesizer lock up times, which preclude scanning.
3.10 NAT NTX138 Wide-band/Narrow-band Operation
The NAT NTX138 radios are capable of operating in either a wideband mode (5.0 kHz
modulation) or narrowband (2.5 kHz modulation) mode. These modes are largely
determined by the operating system used by the radio, and the associated channel
spacing.
See section 3.7.1 for wide/narrow band display indication.
Page 3-28 Jan 4, 2006
ENG-FORM: 806-0106.DOT
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