Nautel VS300, Operation And Maintenance Manual

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VS300 Operations and Maintenance Manual Operating the transmitter
Page 2-58 Issue 8.0 2016-03-01
– HD PA Volts: for FM+HD, HD and DRM+ modes, enter value, in volts, between
25.0 V and 53.0 V. This value sets the drain voltage applied to the PAs in the RF power
modules, from their associated power supplies. This value affects IBOC/DRM+
performance. Larger values result in an improved spectrum, but decreased efficiency.
Conversely, smaller values result in improved efficiency, but degrade the spectrum.
Typical values are between 35 V and 50 V, and depend on many variables such as power
level, frequency and injection level.
– HD Power Boost Priority: for FM+HD mode only, select either MER (modulation error
ratio; default setting) or Efficiency.
Selecting Efficiency enables Nautel’s digital PowerBoost process, an advanced peak-
to-average power ratio reduction that prioritizes efficiency and power capability when
reducing the peak-to-average power ratio, while ensuring that the MER of the
transmitted HD signal meets transmission requirements. HD PowerBoost is only
available to transmitters with the appropriate licensing.
Selecting MER effectively disables the PowerBoost function and makes maximizing
MER the priority. Transmitter efficiency and power capability will be reduced as a
result.
Note:
The actual digital sideband power is 3 dB less than that indicated in the upper or lower IBOC
Injection fields; i.e. if -20dBc is entered in the upper and lower IBOC Injection fields, the upper
and lower digital sideband power levels are actually -23dBc; this way, when added, the resultant
total digital power level is -20dBc.
For symmetrical sideband transmission: if -14dBc IBOC Injection level is desired (total digital
power of upper + lower sidebands is 4% of analog carrier power), set the upper and lower IBOC
Injection levels to -14dBc.
For asymmetrical sideband transmission, consider that the actual sideband power level is 3dB less
than that shown. For example, if the upper digital sideband IBOC Injection level is entered as -
14dBc, the actual power level will be -17dBc. This is equally true for the lower digital sideband.
Note:
The preferred option to maximize IBOC performance is by using the HD Optimizer feature (see
“Spectrum/Efficiency Optimizer” on page 2-105 . In this case, leave PA Volts setting at its
default value (53.0 V).