Nautel NV15, Руководство по эксплуатации и обслуживанию

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NV15/NV20 Operations and Maintenance Manual Operating the transmitter
Issue 3.2 2013-10-01 Page 2-73
Exciter TCXO
This system setting allows users to calibrate the internal clock to a user supplied external high
precision 10MHz clock reference (e.g. GPS synchronized 10MHz clock). Once this external 10MHz
clock reference is connected, the
10MHz Int-Ext Offset
field will display the difference between the
internal and external frequencies (in ppm). Users can press the
Start
button to automatically calibrate
the internal TCXO to the external reference source; equally, they can manually enter the measured
internal-external offset value into the
TCXO Offset Value
field and press
Apply
.
If no external high precision 10MHz clock reference is connected, but the actual transmitter carrier
frequency is being measured with a calibrated external frequency counter, operators can manually
offset the internal TCXO by entering the appropriate ppm difference in the
TCXO Offset Value
field.
For example, if the frequency of the transmitter is 1 ppm too high, then a positive 1 ppm should be
entered in the
TCXO Offset Value
field in order to compensate. Similarly, if the transmitter frequency
is too low, enter a negative ppm value. After an adjustment is made, press
Apply
.
To calibrate another exciter, switch to that exciter and repeat the calibration.
Figure 2.54: System Settings - Exciter TCXO
IBOC settings
This system setting (see Figure 2.55 on page 2-74 ) allows users to establish Forward Tap Delay,
FM+HD Low Inj Gain, FM+HD High Inj Gain and HD only system Gain levels. It also allows for
an IBOC power calibration. Changes apply to the active exciter (A or B) only. To calibrate the other
exciter, switch to the other exciter and repeat the change.