Comtech EF Data CDM-700 - Manual (Page 67)

CDM-700 High Speed Satellite Modem Revision 5
Front Panel Operation MN/CDM700.IOM
6–13
If Tx Modulation Æ Inv is selected:
Tx Spectrum: Normal
Inverted (E)
When Normal is selected the spectral sense of the carrier has the default transition to I and Q
constellation points. Selecting Inverted causes the I and Q transition points to move in the
opposite sense. The selection of the Inverted also can correct for spectral inversion in the uplink
or downlink.
Select Normal or Invert using the ◄ ► arrow keys. Press
ENTER
.
If Tx Modulation Æ
α is selected:
Tx (α) Rolloff %: 25 35
(E)
The Rolloff, or
α, dictates how fast the spectral edges of the carrier are attenuated beyond the
3dB bandwidth. The default setting is 25%; with 25% rolloff, the edge falls off more quickly
than with the 35% setting.
Select the Rolloff (
α) setting using the ◄ ► arrow keys. Whenever the Mode is changed, (α)
reverts to 25%, but ( α) can be modified to 35% from this menu. Press
ENTER
.
Tx: Æ Code
Tx Code Rate: 3/4 7/8
(E)
Refer to data rate menu for valid code rates.
IMPORTANT
• All possible choices are presented at all times.
• If an option is not installed (either Hardware or FAST) or is not valid, or if a
code rate is not available for the Mode selected, the ◄ ► arrow keys will
force the cursor to skip past the unavailable choice.
Select the code rate by using the ◄ ► arrow keys. Press
ENTER
.
Tx Code Rate Selection Description
3/4 Valid for all Modulation Types
7/8 Valid for all Modulation Types (actual 20/23)