Nautel VS1 - Page 83

VS1 Operations and Maintenance Manual Operating the transmitter
Issue 3.1 2013-10-01 Page 2-55
Mode - additional calibration settings:
– IBOC Injection (Lower): for FM+HD and HD modes, enter value, in dB, between -20
and -10 dB for the IBOC injection level of the lower sideband of digital carriers. This
value determines the relationship between the digital carriers power and the analog
carrier power. Example: -20 dB indicates that the total RMS power of the digital carriers
will be 1/100 of the total RMS power of the analog carrier. -10 dB indicates that the total
RMS power of the digital carriers will be 1/10 of the total RMS power of the analog
carrier.
– IBOC Injection (Upper): for FM+HD and HD modes, enter value, in dB, between -20
and -10 dB for the IBOC injection level of the lower sideband of digital carriers. This
value determines the relationship between the digital carriers power and the analog
carrier power. Example: -20 dB indicates that the total RMS power of the digital carriers
will be 1/100 of the total RMS power of the analog carrier. -10 dB indicates that the total
RMS power of the digital carriers will be 1/10 of the total RMS power of the analog
carrier.
– 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.
Note:
The actual digital sideband power is 3dB 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, account for the fact 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.