Nautel NV30 - Page 85

NV30/NV40 Operations and Maintenance Manual Operating the transmitter
Issue 3.3 2014-12-10 Page 2-67
IPA bias balance
IPA Bias Balance (see Figure 2.49 on page 2-68) allows for optimal balancing of RF power module
outputs to minimize reject load power. An
IPA Balancing Recommended Alarm will be generated
when balancing is suggested. This may occur after an RF power module has been replaced or
repaired. While RF is enabled (on) and the transmitter is operating at the desired power level in the
desired preset, press the
Start button to initiate the process. When the process has been completed,
the Save and Cancel buttons will activate to either save the result to the active preset or abort the
function without affecting the previous balance. Note that the user may press Stop while a balancing
is in process but still save or cancel the interim result.
The balancing progress may be observed by monitoring the Reject Power Percentage meter.
Balancing targets a reject power percentage of 0.75% or less of the transmitter’s maximum power
capability. (An IPA Balancing Recommended alarm will be generated if this percentage exceeds
1.5%.)
While this routine can be performed when operating in most presets (as the DAC bias numbers are
stored in the controller’s EEPROM), it should also be noted that this balancing process affects only
the active preset.
Users may also adjust the bias values individually to either a user specified value or to the default
value saved in that module’s EEPROM (see Factory Settings - PA Field Bias on page 2-69). Note, that
if an auto-balance is started any user set values will be replaced with default values before the process
starts. Therefore, manual adjustment should be undertaken only after an auto-balancing has been
completed or manually stopped.
Note:
IPA bias balancing cannot be performed when the transmitter is in the Current Settings preset.
Users must have an active preset saved (without edits) in order for the updated IPA bias data to
be stored properly. IPA bias balancing can also not be performed if there is a module fault present
(e.g. PA fail).