User's Guide

Page 3
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Transceiver Variants
Two variants of the T6TR VHF transceiver are available:
❑ B6550/NB/50. This transceiver frequency operating range is 118.000 to 136.975 MHz. Power
output adjustable from 5 to 50 Watts. Frequency stability compliant with ICAO requirements for 2,
3 and 4-offset carrier applications
❑ B6550/WB/50. This transceiver frequency operating range is 112.000 to 155.975 MHz. Power
output adjustable from 5 to 50 Watts. Frequency stability compliant with ICAO requirements for 2,
3 and 4-offset carrier applications.
Operating Frequency
The transceiver’s operating frequency can be changed by the user through the front panel, through the
VFP, through a T6 controller or through an associated MARC system (or compatible control data
system). Details of how to change the operating frequency from the front panel and VFP are contained
in this document. Details of how to change the frequency from MARC or a T6 controller can be found in
the MARC and T6 Controller User Guides respectively.
Input Supplies
The transceiver can be operated from standard ac input supplies, or from a low voltage dc supply. Both
ac and dc input supplies can be connected to the equipment. When both ac and dc supplies are
connected, operation from the ac supply takes priority; automatic change-over to the dc supply will occur
if the ac supply fails. On restoration of the ac supply, the equipment reverts to ac operation.
Built-in Test (BIT) Indications
The transceiver continuously self monitors key internal parameters without affecting normal operation. If
a BIT alarm is detected, the front panel Alarm indicator lights, the Ready indicator becomes unlit, and the
transceiver becomes inoperable. Additionally, a BIT alert, as opposed to a BIT alarm may be indicated.
A BIT alert is shown by the front panel Alarm indicator flashing; the Ready indicator remains lit and the
transceiver remains operational, but at reduced power. Conditions that cause a BIT alert are:
❑ RF output has reduced from its setting by more than 3 dB
❑ Supply volts has fallen below a pre-defined level.
In AM-voice and AM-MSK modes only, and in addition to continuous monitoring, an interruptive BIT test
can be initiated locally at the front panel or remotely. When initiated, test signals are injected that key the
transceiver allowing parameters to be monitored in their active state.
The results of continuous monitoring, and of interruptive testing, are available at the front panel LCD and,
if connected, the VFP PC. When the transceiver is used with a MARC system (or other compatible data
and control system) the results are also sent, in the form of a data message, to the monitoring facility.