Codan Radio Communications VT-3-150-SN User Manual
VHF Enhanced Transmitter Instruction Manual VT-3 132 - 174 MHz
2-5
2.3.2
Frequency Change
The transmitter is initially aligned at the factory for the frequency stamped on the 'Factory Set
Operating Frequency' label (see section 3.1). This label should list the frequency at which the last
complete transmitter alignment was performed. For a small frequency change, a simple channel
change (see section 2.2) may be all that is required. A larger frequency change may involve the
realignment of other modules. The frequency change in question is the accumulated frequency
change in relation to the frequency stamped on the label. For example, if the frequency is changed
by 0.5 MHz from that stamped on the label, then a second frequency change of 1 MHz in the same
direction would result in a total change of 1.5 MHz. The action taken would be on the basis of the
1.5 MHz value. Failure to perform a realignment after a large frequency change could result in
unreliable transmitter operation or transmitter operation that does not conform to the published
specifications. The allowable frequency change is summarized below.
Operating Frequency' label (see section 3.1). This label should list the frequency at which the last
complete transmitter alignment was performed. For a small frequency change, a simple channel
change (see section 2.2) may be all that is required. A larger frequency change may involve the
realignment of other modules. The frequency change in question is the accumulated frequency
change in relation to the frequency stamped on the label. For example, if the frequency is changed
by 0.5 MHz from that stamped on the label, then a second frequency change of 1 MHz in the same
direction would result in a total change of 1.5 MHz. The action taken would be on the basis of the
1.5 MHz value. Failure to perform a realignment after a large frequency change could result in
unreliable transmitter operation or transmitter operation that does not conform to the published
specifications. The allowable frequency change is summarized below.
Note: It is advisable to confirm these frequency ranges with the individual module manuals,
notably the Amplifier and Synthesizer Module, as they are subject to change with updated
versions. The values in the module manuals take precedent over those tabulated.
versions. The values in the module manuals take precedent over those tabulated.
FOR MODEL ALL VT-3 132 - 174 MHz Transmitters
Size of Frequency Change Modules to be Aligned
less than ± 0.2 MHz
Transmitter Main Board (Channel Change)
between ± 0.2 and ± 0.5 MHz
Transmitter Main Board (Channel Change),
Audio Processor (see section 2.3.4)
Audio Processor (see section 2.3.4)
between ± 0.5 and ± 1.0 MHz
Transmitter Main Board (Channel Change),
Audio Processor (see section 2.3.4), Synthesizer
check RF alarm thresholds (section 2.3.5)
Audio Processor (see section 2.3.4), Synthesizer
check RF alarm thresholds (section 2.3.5)
± 1.0 MHz or greater
Complete alignment
2.3.3
Output Power Adjustment
The RF power output of the amplifier is set to its rated value of 2.0 Watts or 8.0 Watts at the
factory. This should not require adjustment under normal circumstances. However, should it be
necessary to correct the output power, the 'Output Power Adjustment' which is described in the
Amplifier Manual can be adjusted accordingly. If the Synthesizer module is replaced, it is strongly
recommended that the amplifer undergo a realignment as described in the Amplifier Module, unless
it is confirmed that the original and replacement Synthesizer module have identical output power
(within ± 0.5 dBm).
factory. This should not require adjustment under normal circumstances. However, should it be
necessary to correct the output power, the 'Output Power Adjustment' which is described in the
Amplifier Manual can be adjusted accordingly. If the Synthesizer module is replaced, it is strongly
recommended that the amplifer undergo a realignment as described in the Amplifier Module, unless
it is confirmed that the original and replacement Synthesizer module have identical output power
(within ± 0.5 dBm).